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Energy shortages and the global climate crisis have led researchers to develop renewable clean energy sources. Zinc-air batteries have attracted much attention due to their high theoretical energy density, safety, and conversion efficiency. However, the cathodic oxygen reduction reaction (ORR) exhibits slow reaction kinetics and high reaction energy barriers, which require catalysts with high activity, selectivity, and stability to improve the reaction rate. Chainmail catalysts have attracted attention in the field of energy conversion and storage due to their structural stability. In this paper, coal-based carbon encapsulating Co-N-C chainmail electrocatalysts are designed and constructed, which can effectively reduce the thermal crumpling phenomenon of the framework structure, enhance the defect content and provide active sites for ORR. The results show that G/Co-N-C-0.025 exhibits a higher half-wave potential than that of Pt/C, with a high ultimate current density of 4.6 mA cm−2, good cycling stability, and high methanol resistance. A primary zinc-air battery is assembled, with an open-circuit voltage of 1.417 V and a maximum power density of 82 mW cm−2. The specific capacity is 789.2 mAh g−1 at a current of 20 mA cm−2. This work provides new ideas for the design and application of high-performance chainmail electrocatalysts. [Display omitted] • Coal-based carbon encapsulating Co-N-C chainmail electrocatalysts are designed. • It exhibits the excellent catalytic activity for 4e oxygen reduction reactions. • The performance of assembled zinc-air battery is comparable to that of Pt/C. [ABSTRACT FROM AUTHOR]

The crux to promote the utilization of air-cathode microbial fuel cell (AC-MFC) is to find high-efficiency and low-budget oxygen reduction reaction (ORR) catalysts, which can replace Pt-based catalysts, reduce electrode cost and thus improve the cost-effectiveness of AC-MFC. In this work, a three-dimensional network carbon structure F-MIL-HOF loaded with Fe 2 O 3 material composites have been successfully synthesized by carbonizing by NH 4 F-fluorinated MIL-88B combined with a high nitrogen content hydrogen-bonded organic framework (HOF) to evince excellent catalytic property for ORR in both alkaline and neutral electrolytes. The Fe 2 O 3 obtained after carbonization of MIL-88B portrays efficient ORR catalytic activity, and the combination with the natural pore-rich HOF precisely solves the problems of uncontrolled growth and agglomeration during Fe 2 O 3 synthesis, achieving the high dispersion and full exposure of Fe 2 O 3 nanoparticles as active sites. As-synthesized F-MIL-HOF as cathodic catalyst reaches a limiting current density of 6.40 mA cm−2 in alkaline condition, which exhibits an advantage performance over commercial Pt/C (6.26 mA cm−2). Furthermore, F-MIL-HOF shows approximately four-electron pathway with better methanol resistance and stability than Pt/C, and the performance only decreases by 10.2 % in the stability test, which still had efficient ORR catalytic performance. F-MIL-HOF is an emerging alternative electro-catalyst for AC-MFC. • F-MIL-HOF is an F-modified Fe–N–C material. • MIL-88B pyrolysis produces Fe 2 O 3 active sites to promote mass transfer. • F modification increases the stability and corrosion resistance of F-MIL-HOF. • The synergistic effect of F and N element can reduce the activation barrier. • F-MIL-HOF has outstanding ORR performance in MFC compared with Pt/C. [ABSTRACT FROM AUTHOR]

Electrocatalysts play a pivotal role in advancing proton-exchange membrane fuel cell (PEMFC) for hydrogen energy applications. In this study, we investigate a novel PtCu/C N electrocatalyst synthesized via a gram-scale synthesis approach, which demonstrates remarkable activity and stability in the oxygen reduction reaction (ORR). The catalyst's effectiveness stems from its unique structure, combining bimetallic nanoparticles (NPs) and an N-doped carbon support. Employing identical location transmission electron microscopy (IL-TEM) imaging, we observe significant NP structure reorganization upon activation influenced by the upper limiting potential. Notably, the PtCu/C N catalyst activated to 1.0 V surpasses the United States Department of Energy (DOE) target for ORR activity by 3.3-fold. These findings underscore the potential of this catalyst in enhancing the performance of PEMFCs, marking a significant advancement in hydrogen energy technology. [Display omitted] • Catalyst's effectiveness attributed to unique structure of bimetallic NPs and N-doped support. • Vital reorganization of NPs occurs under the upper limiting potential of activation. • PtCu/C N catalyst activated to 1.0 V surpasses DOE target for ORR activity by 3.3-fold. • IL-TEM method comes to the rescue in assessing NPs' reorganization. • Findings highlight potential of bimetallic catalyst in enhancing PEMFC performance. [ABSTRACT FROM AUTHOR]

Enhanced ordered intermetallic compounds excel in catalyzing the oxygen reduction reaction (ORR). We introduce a novel synthesis strategy based on molecularly engineered to address challenges in high-temperature annealing. It involves the synthesis of carbon platforms with rich edge sites, which serve as effective anchoring points for nanoparticles. By utilizing sulfur anchoring, we synthesize ordered Pt–Co intermetallic with Pt-rich shells (o-PtCo@Pt) that exhibit remarkable ORR performance. Ordered arrangement of Pt–Co endows Pt-shell with compression stress and enhances the oxidation resistance of Pt/Co sites. O–PtCo@Pt exhibits high mass activity (MA, 0.53 A mg Pt −1) and specific activity (SA, 1.17 mA cm−2). It exhibits remarkable as cathodic catalyst in proton exchange membrane fuel cells. It achieves power density of 1.14 W cm−2 at 2.0 A cm−2, with MA of 0.50 A mg Pt −1 at 0.9 V. It maintains stability with only 8 % power density loss after 30,000 cycles, retaining MA of 0.35 A mg Pt −1. • O–PtCo@Pt with highly ordered and stable Pt-shell was synthesized. • S was introduced within a carbon platform to anchor O–PtCo@Pt nanoparticles. • The catalysts exhibited excellent ORR activity and strong durability. [ABSTRACT FROM AUTHOR]

Advancements in solar-driven energy storage technology have been achieved for rechargeable zinc-air batteries (RZABs), facilitating accelerated kinetic responses in both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In this study, we successfully synthesized a novel g-C 3 N 4 /BiOBr/Bi 2 O 2 CO 3 ternary heterojunction through a facile hydrothermal process, demonstrating its efficacy as a bifunctional photocatalyst. Upon exposure to LED irradiation, this heterojunction triggers an effective separation of the photogenerated electron-hole pairs, resulting in enhanced oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) performance by 46.19 % and 65.69 % respectively, compared to non-LED conditions. Interestingly, the reduction in the potential gap under LED irradiation (0.06 V), correlating with a significant 2.71 % increase in round-trip efficiency (RTE), is observed. In addition, the optimized band alignment derived from g-C 3 N 4 /BiOBr/Bi 2 O 2 CO 3 ternary heterojunction for photo-assisted charging rechargeable zinc-air batteries is proposed. Insightfully, photo-enhanced charging in RZABs mechanism during the charge/discharge process through in-situ X-ray absorption spectroscopy (XAS) is monitored, confirming the large interaction between O 2 adsorption and Bi 6d orbitals of g-C 3 N 4 /BiOBr/Bi 2 O 2 CO 3 in the presence of LED. In conclusion, our innovative g-C 3 N 4 /BiOBr/Bi 2 O 2 CO 3 ternary heterojunction underscores the significant role that visible-light-driven photocatalysts can play in enhancing the efficiency of rechargeable zinc-air batteries. [Display omitted] • Photo-assisted RZAB is first reported for the g-C 3 N 4 /BiOBr heterojunction. • The limited current of ORR and OER are increased by 46.19 % and 65.69 % under LED. • Round-trip efficiency under LED irradiation is enhanced by 2.71 %. • The band alignment and mechanism of a photo-assisted RZABs are first proposed. • In-situ XAS reveals the enhanced absorption of O 2 on Bi atom under LED. [ABSTRACT FROM AUTHOR]

A spectrum of selenium-doped Fe–N–C catalysts is prepared and scrutinized for acidic oxygen reduction reactions to understand the impact of the presence and amount of chalcogen dopants on the catalytic performance as cathode catalyst layers (CCLs) for H 2 –O 2 and H 2 –air polymer electrolyte membrane fuel cells (PEMFCs). While for a high initial content of Se, all available iron is bonded into iron selenides, a low amount of Se doping yields Fe–N–C catalysts of extensive microporosity, increased nitrogen content, and iron occurring predominantly in the Fe-N x coordination state. The chemistry of the iron-carbon-selenium (Fe–C–Se) system is studied in detail to elucidate the impact of Se on Fe–N–C catalyst formation during pyrolysis. The performance of the Se-doped platinum group metal-free Fe–N–C catalysts in PEMFCs is compared with their commercially available counterpart. The effect of the catalysts' morphology alternation by ball-milling on their performance is also studied. It is concluded that chalcogen doping (either S or Se doping) indirectly impacts Fe–N–C catalyst activity by controlling carbon scaffold properties, while the idea of a direct impact of chalcogen atoms on the Fe-N x catalytic centers is challenged. [Display omitted] • Se-doped Fe–N–C catalysts are studied as CCLs in H 2 –O 2 and H 2 –air PEMFCs. • Se-content is varied in a wide range, yielding a large family of Se-doped Fe–N–C. • Se doping grants enhanced microporosity and formation of Fe–N x sites. • Common characteristics of chalcogen-doped Fe–N–C catalysts are identified. • Ball-milling alters catalysts' morphology, thus improving their activity. [ABSTRACT FROM AUTHOR]

Developing electrocatalysts with efficient cathode oxygen reduction reaction (ORR), for example, iron-based single-atom catalysts (Fe-SACs), has been deemed necessary to accelerate the commercialisation process of zinc (Zn)–air batteries. Nevertheless, determining how various nitrogen species and active metal centres coordinate on an atomic scale remains unclear and inadequately explained. Herein, we demonstrate a soft-template-aided technique using Fe-containing molecules (e.g. iron phthalocyanine [FePc], Fe-1,10-phenanthroline [Fe-Phen] and Fe-glucose) to enhance the performance of Fe-SACs in terms of ORR. In this technique, FePc molecules can be converted into atomically dispersed pyrrolic-type iron–nitrogen (FeN 4) sites during a pyrolytic process. The resultant catalyst exhibits excellent ORR activity (half-wave potential = 0.90 V) in alkaline medium and standing battery performance when used in Zn–air batteries (peak power density = 197.3 mW cm−2 and specific capacity = 796.2 mAh g−1). As per the findings from control experiments and characterisation studies, electron transfer between the support and the active Fe centre amplifies the ORR performance. Theoretical calculations substantiate that Fe sites coordinated with pyrrolic N atoms govern the electronic configuration of the catalysis, reducing the free energy absorption of reaction intermediates and thus increasing its intrinsic ORR capability. Herein, we aim to offer a fresh perspective on the relation between coordination environments and catalytic activity in ORR catalysts. • Pyrrolic-type FeN 4 act as active sites in FePC–CNN. • The thermal exfoliation of the support prominently increases the surface area. • The role of different N species or the oxygen reduction reaction (ORR) are clarified. • As the attractive catalyst for ORR, FePC–CNN shows great potential for Zn-air battery. • This work provides deeper understanding of coordination−activity relationships. [ABSTRACT FROM AUTHOR]

This work explores a novel and sustainable synthesis strategy for developing platinum-group metal (PGM)-free catalysts with high electrocatalytic activity, emphasizing the significance of hierarchically porous structures to improve electrocatalytic performance. We present an easily scalable method that utilizes magnesium salt as the precursor of sacrificial template to synthesize mesoporous carbon-based catalysts. The catalysts are doped with nitrogen and iron, while manganese is added to increase the stability of the catalyst under highly corrosive acidic conditions. The electrochemical oxygen reduction reaction (ORR) is investigated in acidic media using the rotating disk electrode technique. The electrocatalytic activity of the prepared catalysts is evaluated in proton exchange membrane fuel cell (PEMFC), where a significant increase in performance is achieved with the hierarchically porous carbon catalyst. The results demonstrate the potential of these catalysts as efficient and durable alternatives to PGM-based cathode catalysts in PEMFCs. [Display omitted] • Mesoporous catalysts are prepared from alkylresorcinols using an Mg-based template. • High ORR activity of Fe- and FeMn-doped M-N-C catalysts in RDE test in acidic media. • FeMn-doped electrocatalyst exhibits increased stability in AST and low H 2 O 2 yield. • Excellent PEMFC results were obtained using PGM-free materials as cathode catalysts. [ABSTRACT FROM AUTHOR]

The long-term operation of fuel cell vehicles causes aggregation and dissolution of Pt nanoparticles and corrosion of the carbon support of fuel cell cathode catalysts. However, thoroughly addressing these issues is challenging. Herein, we report a high-performance carbon-supported Pt 3 Co intermetallic catalyst by depositing ultrafine CeO 2 nanocrystals on a porous carbon, then the ordered Pt 3 Co alloy nanoparticles are loaded on the CeO 2 /C support. The resulting O-Pt 3 Co-CeO 2 /C catalyst with 30 % CeO 2 loading exhibits high mass activity (MA) and low MA loss (8.44 % after 30000 low-potential cycles, 17.62 % after 5000 high-potential cycles), outperforming commercial Pt/C (a 53.46 % loss at 30000 low-potential cycles, a 29.23 % loss at 5000 high-potential cycles). Importantly, we find that the generate heterojunction interface between CeO 2 and Pt 3 Co increases the Pt oxidation potential and decelerates the electro-oxidation reaction of carbon oxides, thereby markedly countering carbon corrosion. Furthermore, when O-Pt 3 Co-30%CeO 2 /C is used as cathode catalyst, the membrane electrode assembly with Pt loading of 0.15 mg cm−2 delivers a rate power of 1.19 W cm−2, and potential loss of only 9.09 mV at 0.8 A cm−2 after 30000 square-wave cycles. This study describes a blueprint for the target improvement of the durability of fuel cell catalysts through the design of carbon supports. This work is designed carbon-supported CeO 2 -Pt 3 Co composite catalyst for durable ORR catalysis, which not only significantly improved the activity and stability of ORR in MEA but also uncovers the mechanisms of corrosion resistance of carbon. [Display omitted] • CeO 2 nanocrystals (∼4.5 nm diameter) were uniformly dispersed on porous carbon. • High-performance ORR catalyst was obtained by deposition of Pt 3 Co NPs on CeO 2 /C. • The heterojunction interface between Pt 3 Co and CeO 2 NPs was confirmed via TEM. • CeO 2 and ordered Pt 3 Co NPs improve the durability of catalyst at low-potential. • The corrosion of the catalyst support in high-potential ADT was inhibited by CeO 2. [ABSTRACT FROM AUTHOR]

A facile dual isolation and protection strategy is developed to prepare PtFe intermetallic electrocatalyst (PtFe–N–C@bioC) on porous biomass carbon (bioC) derived from peanut shell. In preparation, meso-tetraphenylporphyrine (H 2 TPP) together with platinum (II)-tetraphenylporphyrin (PtTPP) are in-situ fabricated on the porous peanut shell-derived bioC matrixes and then further absorbed Fe (III) tetraphenyl porphyrin (FeTPP) molecules through π−π interactions between PtTPP/H 2 TPP and FeTPP to form a mixed precursor of FeTPP/PtTPP/TPP-bioC. Upon pyrolysis of FeTPP/PtTPP/TPP-bioC, PtFe bimetallic-containing N-doped carbon formed on bioC (PtFe–N–C@bioC). The resultant PtFe–N–C@bioC showed excellent oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) activity across a wide pH range. In particular, under alkaline medium, PtFe–N–C@bioC shows the ORR performance with an onset potential (E onset) of 0.989 V, a half-wave potential (E 1/2) of 0.901 V and a limiting current density (J L) of −6.214 mA cm−2. Meanwhile, PtFe–N–C@bioC delivers an enhanced mass activity (1.197 A mg−1 Pt), which is 13 times larger than commercial Pt/C. For HER, PtFe–N–C@bioC shows an impressive overpotential (η 10) of 17 mV at a current density of 10 mA cm−2 under acidic medium. Further, it is applied to Zn-Air batteries with a power density performance of 98.7 mW cm−2 and good durability. • A facile dual isolation and protection strategy is developed. • Highly efficient dispersion of PtFe intermetallic electrocatalyst is obtained. • The bio-derived PtFe–N–C@bioC catalysts exhibit high performance for ORR and HER. [ABSTRACT FROM AUTHOR]

The Pt 1 /CeO 2 single-atom catalyst excels across catalytic fields, promising applications in the oxygen reduction reactions (ORRs). Here, we employ first-principles calculations to systematically investigate the ORR mechanism catalyzed by Pt 1 /CeO 2 systems and the activity regulated by Ce3+ polarons. We determine the reaction pathways of different Pt 1 /CeO 2 systems by evaluating four critical factors: O 2 adsorption energy, O 2 dissociation Gibbs barrier, Gibbs free energy change for O 2 →OOH*, and H 2 O 2 adsorption structure. Notably, most Pt 1 /CeO 2 systems tend to react through the 4e− associative path. Theoretical activity calculations reveal that Pt OH /CeO 2 (110) system show low overpotential of 0.47 V comparable to pure Pt. The excellent ORR activity is attributed to the synergistic mechanism of Pt and surrounding Ce3+ polarons, where the polaron regulation mechanism dominates the reaction. The quantity of Ce3+ polarons not only affects the reaction active sites but also regulates the radical adsorption state. With an elevated Ce3+ polarons concentration, the ORR overpotential in Pt 1 /CeO 2 system can decrease from 0.47 to 0.16 V, leading to a substantial enhancement in activity. This work first underscores the crucial involvement of Ce3+ polarons in catalyzing the ORR, reducing the significance of Pt in catalysis, inspiring a new way to design active non-platinum electrocatalysts for ORR in experiments. [Display omitted] • Four key factors determining the ORR pathways of Pt 1 /CeO 2 systems were deduced. • Most Pt 1 /CeO 2 systems prefer to react through the 4e− associative pathway. • Pt OH /CeO 2 (110) system with high stability shows the best ORR catalytic activity. • The Ce3+ polaron regulation mechanism was proposed to dominate the reaction. [ABSTRACT FROM AUTHOR]

The formation of small-sized (<5 nm) and high-loading (>50 wt%) Pt-based intermetallic compound structures commonly requires thermal treatment to conquer the atom-ordering barrier, which inevitably causes severe nanoparticle agglomeration and hence reduces oxygen reduction reaction activity. Herein, we provided a synthetic wrinkled carbon support by vapor deposition from methane (CH 4), and then we utilized the carbon to synthesize sub-5 nm high-loading (50.6 wt%) Pt 3 Co 1 intermetallic compound by mesoporous confinement effect. Structural characterizations reveal that the nanoparticles are mainly located in the pores of the mesoporous carbon with an average size of ca. 4.1 nm, corroborating the confinement effect of the mesoporous structure. As a consequence, the Pt 3 Co 1 intermetallic compound catalyst exhibits superior oxygen reduction reaction activity with a mass activity (@0.9V) of 0.35 A/mg Pt and satisfactory durability with a mass activity decline by 22% after 40k-cycles accelerated durability test. Membrane electrode assembly with the resultant catalyst delivers the desirable performance with the peak power density of ca. 1.0 W/cm2 while lowering the Pt loading to 0.1 mg/cm2, suggesting the practical application potential in low-Pt proton exchange membrane fuel cells. • Wrinkled carbon with abundant mesopores of ca. 4 nm is synthesized to confine IMC NPs. • 50.6 wt% Pt 3 Co 1 -IMC with an average size of ca. 4.1 nm is prepared. • Pt 3 Co 1 /MPC with a MA decline by only 22% after 40k-cycles accelerated durability test. • MEA with 0.1 mg Pt /cm2 Pt 3 Co 1 /MPC attains the peak power density of ca. 1 W/cm2. [ABSTRACT FROM AUTHOR]

Efficient and stable electrocatalysts with low platinum content are crucial for the practical application of fuel cells. The development of Pt-based single atom catalysts (SACs) has emerged as a promising research direction. In this study, we design and prepare a SACs based on MoS 2 with Pt–S–Mo and Pd–S–Mo active sites (Pd, Pt–MoS 2) by successively occupying vacancies, while maintaining the individual characteristics of the active sites. The resulting Pd, Pt–MoS 2 catalyst exhibits excellent electrocatalytic activity for oxygen reduction reaction (ORR), long-term stability, and resistance to common poisons (SCN−, S2−, and methanol) under neutral conditions. Meanwhile, the microbial fuel cell (MFC) equipped with Pd, Pt–MoS 2 exhibits excellent performance in terms of actual electricity generation performance and sewage purification capacity with an ultrahigh power density, average chemical oxygen demand (COD) removal rate, and coulombic efficiency (CE) of 1398.6 ± 43.5 mW m−2, 96.2 ± 2.2 %, and 22.5 ± 0.5 %, respectively. This strategy will provide new insights into the development of advanced bimetallic as well as polymetallic doped vacancies of MoS 2 SACs. [Display omitted] • A feasible approach for the design of bimetallic single atom catalysts. • One SACs based on MoS 2 was prepared by successively occupying vacancies. • Pd, Pt–MoS 2 catalyst exhibits excellent electrocatalytic activity for ORR. • Optimized catalyst exhibits excellent capacity in electricity generation. [ABSTRACT FROM AUTHOR]

Protonic ceramic fuel cells (PCFCs) have been the focus of research due to their advantageous properties compared to oxygen ion-conducting solid oxide fuel cells (SOFCs). However, the biggest obstacles to the development of PCFC are the lower proton conductivity and the poor stability in high concentration steam environment. Herein, we report a novel composite cathode with surface reconfiguration, comprised of BaCoO 3-δ (BCO) nanoparticles by water-induced precipitation and Ba 0.9 Pr 0.1 Co 0.7 Fe 0.2 Y 0.1 O 3-δ (BPCFY) substrate with e−/O2−/H+ triple conducting behavior, exhibiting high catalytic activity towards oxygen reduction reaction (ORR) and stability in high steam concentration. With wet hydrogen (3 vol% H 2 O) as fuel and wet air (3 vol% H 2 O) as oxidant, the peak power density of NiO-BZCYYb|BZCYYb|BPCFY single cell reaches 750 mW•cm−2 at 700 °C, approximately 25 % higher than that using dry air at cathode side. Such improvement performance can be attributed to the precipitation of BaCoO 3-δ nanoparticles that increase the active adsorption sites as well as the increased oxygen vacancy concentration by Pr doping in BaCo 0.7 Fe 0.2 Y 0.1 O 3-δ , which synergistically expand the triple phase boundary and facilitate ions migration. This work provided a promising approach to enhance the catalytic activity of PCFC at lower temperatures while also improving its tolerance to steam. • Pr-doping promotes BaCoO 3 nanoparticles precipitation after steam treatment. • Pr-doping improves the ions diffusion process. • The exsolved BaCoO 3 nanoparticles facilitate the gas exchange process. • The composite cathode showed desirable tolerance for steam and carbon dioxide. [ABSTRACT FROM AUTHOR]

Perovskite oxides are widely regarded as efficient and low-cost catalytic materials for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) on the air-electrode side of zinc-air batteries (ZABs). Herein, LaCo 1−x Mo x O 3 (LCM, x = 0, 0.05, 0.1, and 0.15) perovskite electrocatalysts are prepared by self-propagating high-temperature synthesis and evaluated as the bifunctional electrocatalytic activity for ZABs. Results show that the ORR and OER activities of LaCoO 3 (LCO) can be efficiently enhanced simultaneously with the proper substitution of Mo for Co, and the optimal performance is obtained in LaCo 0.95 Mo 0.05 O 3 (LCM-5). In comparison with LCO, LCM-5 demonstrates significantly enhanced bifunctional catalytic activity, in which a more positive ORR onset potential (0.861 V) at −0.1 mA cm−2 and a lower OER overpotential (405 mV) at 10 mA cm−2 are achieved. When using LCM-5 as an air electrode catalyst for ZABs, it delivers a specific discharge capacity of over 800 mA h g−1, a high power density of 136.1 mW cm−2, and excellent long-term cycle stability (120 h at 10 mA cm−2). This finding is primarily due to the regulation of the B-site Co valence states and the increase in surface oxygen vacancies. This study suggests the possibility of enhancing the bifunctional catalytic activity of LaCoO 3 perovskite air electrodes for ZABs by a simple doping process. • Improved catalytic activities toward ORR and OER simultaneously were observed. • The B-site Co valence states and oxygen vacancies were optimized by Mo doping. • The ZABs with LCM-5 as cathode deliver excellent long-term cycle stability. [ABSTRACT FROM AUTHOR]

The commercialization of Proton Exchange Membrane Fuel Cells (PEMFCs) is hindering by the cost of noble metal catalysts. We are introducing A-Fe SAC -NC DS /rGO, a novel catalyst derived from metal-organic framework through carbonization and ammonia treatment. This catalyst is incorporating single iron atoms (Fe SAC) within dual-sized porous nitrogen-carbon frameworks (NC DS , 30 nm and 100 nm), supporting on reduced graphene oxide (rGO). The catalyst is providing abundant active sites, with NC DS increasing active site density and rGO enhancing material conductivity. Consequently, catalyst is exceling in the oxygen reduction reaction, boasting an onset potential of 0.807 V and a half-wave potential of 0.779 V, near benchmark Pt/C catalyst. PEMFC tests employing A-Fe SAC -NC DS /rGO achieved a power density of 780.7 mWcm−2 at 1.6 A cm−2 in an H 2 –O 2 system. In durability tests at 0.6 Acm−2 in H 2 -air, voltage loss was 28.68 % after 50 h. These results position the catalyst as a promising choice for PEMFC. [Display omitted] • A-Fe SAC -NC DS /rGO is derived from carbonization and ammonia treatment of MOFs. • Catalyst has abundant Fe SAC within dual-sized porous N-carbon supported on rGO. • Catalyst exhibits ORR LSV E onset and E 1/2 values close to the benchmark Pt/carbon. • PEMFC demonstrates a power density of 780.7 mWcm−2 at 1.62 Acm−2 in H 2 –O 2 system. • Durability test of PEMFC shows a voltage loss is 28.68 % at 0.6 Acm−2 after 50 h. [ABSTRACT FROM AUTHOR]

Because the mass of lithium-air battery (LAB) changes due to oxygen reduction/evolution reactions (ORR/OER), weighing of the battery is an indispensable method for determining its actual energy density and analyzing the battery reactions. To this end, we have newly developed a weight monitoring system which can trace the semi-permanent weight change of air-batteries (∼11 g including a holder) with a precision of 7.87 μg. The system reveals the weight decrease of LAB in each cycle before finally losing its capacity. The in-situ weighing during battery operation also provides first-hand evidence of double layer capacitance and electrolyte evaporation of LABs. Specifically, the e−/O 2 ratio during discharge is determined to be 1.954 ± 0.004 based on the weight increase of an LAB cell using tetraethylene glycol-based electrolyte at a current density of 100 μA cm−2, confirming the slightly lower e−/O 2 ratio than the ideal two electron ORR. During charge, the initial weight decrease is 5.4% less than the 2e−/O 2 OER process, and the weight decreases sharply at the end of charge due to CO 2 evolution. The main rates of weight increase/decrease remain the same throughout the cycle life, but side reactions are accelerated with cycling, causing the deterioration of LABs. [Display omitted] • An in-situ weighing system for air batteries with 7.87 μg precision was developed. • Weight increase/decrease from oxygen reduction/evolution reactions were observed. • Double layer capacity of air-electrode and electrolyte evaporation were detected. • Continuous weight loss every cycle observed before losing cell capacity. [ABSTRACT FROM AUTHOR]

In this work, we propose hydroxyapatite (HA) as a hard template to unlock the porosity of Fe–N–C catalyst materials. Using HA, a naturally occurring mineral that can be removed with nitric acid, in the synthesis generates a catalyst material with a unique porous network comprising abundant pores and interparticle cavities ranging from 10 to 3000 nm. Hard templating with HA alongside ZnCl 2 as a micropore former results in a Fe–N–C catalyst based on naturally abundant peat with excellent oxygen reduction activity in alkaline conditions. A half-wave potential of 0.87 V vs RHE and a peak power density of 1.06 W cm−2 were achieved in rotating ring disk electrode and anion exchange membrane fuel cell experiments, respectively, rivaling the performance of other state-of-the-art platinum-free catalysts presented in the literature. A combined approach of using renewable peat as a carbon source and HA as a hard template offers an environmentally friendly approach to high-performance Fe–N–C catalysts with abundant porosity. [Display omitted] • Naturally abundant peat converted into highly active Fe–N–C catalyst. • Hard templating with hydroxyapatite generates unique porous network. • Micropore former ZnCl 2 and pyrolysis at 1000 °C promotes formation of active sites. • Peak power density of 1060 mW cm−2 in AEMFC with Fe–N–C cathode. • The result ranks among the 14 best-performing NPGM catalysts in AEMFC. [ABSTRACT FROM AUTHOR]

Over the past few decades, microbial fuel cells (MFCs) have attracted significant interest within the realm of renewable energy technologies owing to their capability to generate electricity from low-grade substrates. However, their commercialization and scaling-up are impeded by significant obstacles, including high capital costs, limited durability, and sluggish oxygen reduction reaction (ORR). Here, we demonstrate an environmentally-friendly approach for developing highly efficient electrocatalysts consisting of palladium oxide (PdO) and different transition metal oxides (i.e., tin (IV) oxide (SnO 2), ceric oxide (CeO 2), iron (III) oxide (Fe 2 O 3), and zinc oxide (ZnO)) embedded within reduced graphene oxide (rGO) framework for improving the efficiency of ORR in neutral medium and MFCs. Among the as-prepared electrocatalysts, the PdO–SnO 2 /rGO possesses the highest ORR electrochemical catalytic activity in a neutral medium (pH ∼ 7.2) following a four-electron ORR pathway, with a current density slightly lower than that of benchmark Pt/C electrocatalyst. The assessment of MFC performance is conducted by employing activated sludge as the inoculum and glucose as the sole electron donor in the anode chamber of single-chamber, air-cathode MFCs. Consistent with electrochemical performance, the maximum power output of an MFC equipped with PdO–SnO 2 /rGO as an air cathode is significantly higher than other tested MFCs, reaching 84.6 ± 2.8 mW m−2, which represents ∼ 91 % of the power output of an MFC with Pt/C air cathode. Our results reveal that the incorporation of PdO into transition metal reduced graphene oxide framework has the potential to facilitate their long-term application as air cathodes in MFCs that possess easy fabrication, relatively affordable cost, and outstanding electrochemical catalytic oxygen reduction capability, for enhancing electricity generation from wastewater. • PdO-MO x /rGO catalysts were prepared using a surfactant-mediated templating method. • PdO–SnO 2 /rGO exhibited high electrochemical activity toward ORR in a neutral medium. • PdO–SnO 2 /rGO has remarkable stability and durability as a cathodic catalyst of MFC. • MFC-PdO-SnO 2 /rGO achieved a comparable power density compared to MFC-Pt/C. [ABSTRACT FROM AUTHOR]

Designing an efficient and stable non-precious metal cathode catalyst is essential to reduce fuel cell cost and promote fuel cell commercialization. Herein, ZIF-67 and carbon powder are rapidly heated using a transient Joule heat device to pyrolyze ZIF-67 to form a CoO/N/C nanocatalysts. The prepared CoO/N/C-90 is comprised of 3–4 nm CoO nanoparticles loaded on a carbon substrate. In alkaline medium the Tafel slope of CoO/N/C-90 is 50 mV dec−1, and a half-wave potential (E 1/2) of 0.82 V towards oxygen reduction reaction (ORR). The E 1/2 only experiences a negative shift of 4 mV after 40,000 cyclic voltammetry (CV) cycles, demonstrating excellent catalytic reaction kinetics and durability. The CoO/N/C-90 is assembled into direct borohydride fuel cells (DBFC) as a cathode, achieving a maximum power density (P max) of 526 mW cm−2 at 60 °C. This work indicates that the CoO/N/C-90 is an efficient and stable non-precious metal catalyst for DBFCs. [Display omitted] • CoO/N/C nanoparticle with a size of 3–4 nm is prepared by CTS method. • CoO/N/C exhibits superior stability and highly electrochemically active area. • A DBFC with maximum power density of 526 mW cm−2 is achieved at 60 °C. [ABSTRACT FROM AUTHOR]

Platinum has been considered as an essential element in both the cathode and anode catalyst in Proton Exchange Membrane Fuel Cells (PEMFC). However, with the increasing capacity of PEMFC industry in both transportation and stationary applications, the demand for platinum increases rapidly. From the standpoint of scarcity and cost, developing platinum group metal free (PGM-free) catalyst is rewarding. In this work, we prepared highly active material with secondary nitrogen doping, and were able to scale up material synthesis from milligram scale to gram scale with the high activity well maintained. The scale up catalyst SU-PAU was evaluated in 50 cm2 MEAs with comprehensive operating and design parameter optimization. The state of art 670 mW/cm2 peak power density was achieved under H 2 -Air operation, with the air partial pressure of 1 bar. • Fe–N–C family PGM-free ORR catalyst synthesis is scaled up from milligram sale to gram scale. • Secondary nitrogen doping creates more micropores and increases ORR activity. • Performance of 50 cm2 MEAs are studied with a variety of testing and design parameters. • State of art PGM-free catalyst based H 2 -Air performance (670 mW/cm2) is achieved. [ABSTRACT FROM AUTHOR]

The cathode properties are critical for solid oxide fuel cells (SOFCs) performance and a major challenge for commercialization. This study employs the impregnation method to produce uniformly distributed Mg-doped manganese-chromium spinel oxide nanoparticles infiltrated into a network on the Gd 0.1 Ce 0.9 O 1.95 (GDC) skeleton as SOFC cathodes. The effects of Mg doping on the performance of these nanostructured spinel oxides are investigated. Both experimental results and density functional theory (DFT) calculations demonstrate that Mg doping can optimize the electronic structure of the manganese-chromium spinel oxide, increase the oxygen vacancy concentration, and significantly enhance the electrical conductivity and oxygen reduction reaction (ORR) catalytic activity. The Mg-doped manganese-chromium spinel oxide cathode exhibits superior performance, with an area-specific polarization resistance of 0.33 Ω cm2 and a maximum power density of 976 mW cm−2 at 800 °C. Moreover, the nanostructures of the cathode barely change after 100 h of cell operation. These findings provide a new strategy for optimizing the performance of SOFC spinel oxide cathodes. • Mg doping lowers bandgap and facilitates oxygen vacancy formation of Mn–Cr spinel. • Mg-doped Mn–Cr spinel cathode exhibits superior performance. • Nanostructures of Mg-doped Mn–Cr spinel remain stable after 100 h cell operation. [ABSTRACT FROM AUTHOR]

Though expensive platinum (Pt) is used as catalyst for oxygen reduction reaction (ORR) in polymer electrolyte fuel cells (PEFCs), insufficient durability remains as a bottleneck for commercialization of PEFCs. Improving both catalytic performance and durability by graphene encapsulation is an attractive strategy to solve this problem. In this study, graphene-encapsulated PtFe core-shell catalyst is synthesized with dimethyl formamide (DMF) and a pair of Pt and Fe electrodes without using any metal salts by utilizing the solution plasma (SP) process. TEM and EELS results show synthesized PtFe nanoparticles are encapsulated with close to single-layered highly crystallized graphene. Although commercial Pt/C showed significant performance degradation (ECSA −33%, MA −68%) after 50,000 cycles of accelerated durability test (ADT), PtFe core-shell catalyst shows remarkably improved durability (ECSA −13%, MA −19%) while graphene shell clearly remains. The improved durability is more prominent in the single cell test, the decrease in maximum power density after 6000 cycles of ADT was significantly lower as −1.2%, compared to that of Pt/C (−52.1%). This study introduces a novel and attractive catalyst synthesis process by the SP method followed by heat treatments and suggests graphene encapsulation can improve long-term durability of catalyst while maintaining ORR activity. • Facile one-step synthesis of graphene core-shell catalyst without using any metal salt. • Removal of nitrogen doping to improve the durability of the graphene shell. • Graphene shell weaken adsorption of Pt-OH ad or other intermediates. • Significant enhancement of durability and power density by graphene encapsulation. [ABSTRACT FROM AUTHOR]

The development of the fuel cell catalysts with high durability and high activity for oxygen reaction reduction remains a great challenge. Various material designs such as alloys, core@shell structure and shape control provide the promising ways to improve the electrocatalytic performance. Herein, on the basis of both the alloy effect and the nanotube structure effect, we demonstrate a high-performance PtNi alloy catalyst with one-dimensional nanotube structure via a galvanic replacement reaction combined with Kirkendall effect. Meanwhile, the PtNi alloy phase and the tube structure are selectively controlled by tuning the PtNi atomic ratio and the wall thickness of the nanotube, respectively. Subsequently, the understanding of the composition effect and the shape effect on the activity and the durability is systematically investigated. The optimized PtNi nanotube catalyst shows significant improvements on the activity (6.2-fold increase in specific activity compared to the commercial Pt/C) and the durability (only 8.6% loss in mass activity after 10000 cycles), attributing to the alloy effect by introducing Ni to the Pt lattice, the Pt-rich surface and the shape effect of the unique one-dimensional hollow tube structure. Image 1 • PtNi alloy NTs are synthesized with tunable compositions and wall thicknesses. • Composition, size and nanotube effects on the performance are systematically studied. • PtNi-NTs show 1.1 times higher in MA and 6.2 times higher in SA at 0.9 V than Pt/C. • PtNi-NTs achieve an enhanced durability of 8.6% loss in MA after 10 k cycles. [ABSTRACT FROM AUTHOR]

The fabrication of low-cost, highly efficient, and earth-abundant electrocatalysts for oxygen reduction reaction is critical to produce clean and sustainable fuel through an electrochemical process. Herein, a facile hydrothermal technique is used for the synthesis of iron sulfide/graphene hybrid for oxygen reduction reaction. Morphological analysis of the resulting catalyst reveals that iron sulfide nanoparticles are homogeneously embedded on the surface of reduced graphene oxide sheet. Electrochemical analysis of the hybrid exhibits remarkably improved catalytic performance for oxygen reduction reaction while achieving half wave potential of +0.845 V and onset potential of +1.0 V (versus reversible hydrogen electrode), along with outstanding long-term stability under alkaline conditions. In addition, the methanol tolerance ability and stability of the hybrid exceed the benchmark platinum/carbon product in alkaline condition. These outstanding activities of the hybrid are attributed to the merits of the interaction between iron sulfide nanoparticles and graphene. The results suggest the practicability of metal sulfide as a low cost and efficient alternative catalyst of platinum for oxygen reduction reaction. Image 1 • Hydrothermal technique is used for fabricating a new iron sulfide/graphene hybrid. • The interaction of mesoporous iron sulfide and graphene produces excellent activity. • The hybrid outperforms Pt/C and other metal sulfide/graphene catalysts towards ORR. • The hybrid's stability and methanol tolerance are superior to Pt/C product. [ABSTRACT FROM AUTHOR]

Calcining pristine metal organic frameworks in an open system to synthesize N-doped carbon materials always lead to some drawbacks, such as relatively low graphitization degree and great loss of heteroatoms, and these factors greatly influenced the oxygen reduction performance of catalysts. In this work, a closed calcination method with three steps pathway has been developed to calcine the in-situ synthesized Co-MOF-GO/Urea composite to obtain the highly graphitized and high N content materials as enhanced oxygen reduction catalysts. During the pyrolysis process, the urea not only served as the additional N source, but also played the role of etching the pore structure by using the produced ammonia gas from polycondensation reaction. After careful adjustment the mass ratio of urea and graphene oxide, a Co-GO-C/N catalyst with high specific surface area, increased N content and abundant of pore structure has obtained. When being used for electrochemistry oxygen reduction reaction, the optimal Co-GO(50)-C/N(2.5) catalyst exhibits almost comparable oxygen reduction performance with the Pt/C in alkaline media, and the onset and half-wave potentials of which are 92 mV and 97 mV higher than that of pristine Co-MOF derived Co-GO(0)-C/N(0) catalyst. In addition, it also exhibits excellent methanol and ethanol tolerance and outstanding long-term durability. Image 1 • Co-GO(m)-C/N(n) was synthesized by using a closed calcination method. • Urea served as additional N source to increase the N atoms content of catalyst. • NH 3 derived from urea polycondensation could etch the pore structure of catalyst. • Co-GO(50)-C/N(2.5) possesses high graphitized and high N content characteristics. • The activity of Co-GO(50)-C/N(2.5)) is higher than that of MOFs derived catalyst. [ABSTRACT FROM AUTHOR]

In recent years, the microbial fuel cell (MFC) technology has drawn the attention of the scientific community due to its ability to produce clean energy and treat different types of waste at the same time. Often, expensive catalysts are required to facilitate the oxygen reduction reaction (ORR) and this hinders their large-scale commercialisation. In this work, a novel iron-based catalyst (Fe-STR) synthesised from iron salt and streptomycin as a nitrogen-rich organic precursor was chemically, morphologically and electrochemically studied. The kinetics of Fe-STR with and without being doped with carbon nanotubes (CNT) was initially screened through rotating disk electrode (RDE) analysis. Then, the catalysts were integrated into air-breathing cathodes and placed into ceramic-type MFCs continuously fed with human urine. The half-wave potential showed the following trend Fe-STR > Fe-STR-CNT ≫ AC, indicating better kinetics towards ORR in the case of Fe-STR. In terms of MFC performance, the results showed that cathodes containing Fe-based catalyst outperformed AC-based cathodes after 3 months of operation. The long-term test reported that Fe-STR-based cathodes allow MFCs to reach a stable power output of 104.5 ± 0.0 μW cm−2, 74% higher than AC-based cathodes (60.4 ± 3.9 μW cm−2). To the best of the Authors' knowledge, this power performance is the highest recorded from ceramic-type MFCs fed with human urine. • Novel iron-streptomycin derived catalyst for ORR in MFCs fed with urine. • The half-wave potential results of Fe-STR show a better kinetic towards ORR. • Fe-STR-based cathodes allow MFCs to reach a power output 74% higher than AC. • The maximum power density output was 104.5 ± 0.0 μW cm−2 by using Fe-STR-cathodes. • MFC performance was stable for 3 months working with Fe-STR-based cathodes. [ABSTRACT FROM AUTHOR]

Abstract Nitrogen-doped carbon matrix (Co/NC) has been synthesized with NaCl as a template and peptone as a carbon/nitrogen source. Subsequently, mesoporous nitrogen-doped CoSe/NC was prepared by solvothermal selenization. The obtained CoSe/NC is useful as highly efficient bifunctional electrocatalyst for hydrogen evolution and oxygen reduction reactions. Structures of the CoSe/NC material have been characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N 2 adsorption desorption analysis and X-ray photoelectron spectroscopy. Results demonstrate the role of NaCl as efficient low cost template to form mesoporous nitrogen doped carbon, which could significantly simplify and reduce the cost of the synthetic procedure. During hydrogen evolution reaction in a 1 M KOH electrolyte, the best performing sample with formula Co 0.88 Se/NC produces an overpotential of 72 ± 0.1 mV at a current density of 10 mA cm−2. This material also shows excellent electrocatalytic activity and stability in oxygen reduction reaction, superior even to a commercial Pt/C catalyst. A primary zinc-air battery containing Co 0.88 Se/NC as a oxygen reduction reaction catalyst reaches an open circuit voltage of 1.44 ± 0.02 V, higher than that of a Pt/C containing zinc-air battery and delivers superior power and current density combination. Graphical abstract Herein, highly efficient mesoporous CoSe/N-doped carbon materials was developed as HER and ORR electrocatalysts for water splitting and zinc-air batteries. Image 1 Highlights • CoSe/NC are developed as catalysts for HER and ORR. • NaCl is used to form the porous structure at high temperature. • Co 0.88 Se/NC displays significantly high electrocatalytic performance. [ABSTRACT FROM AUTHOR]

Abstract The performance of a microbial fuel cell (MFC) that uses an as-prepared zeolitic imidazolate framework-8 (ZIF-8) as air-cathode catalyst is investigated. Due to the composite pore structure, large specific surface area (1416.19 m2/g), and high pore volume (0.55 cm³/g), the 0.5 mg/cm2 ZIF-8 catalyst can enhance the oxygen reduction reaction (ORR) in electrodes and achieve a maximum power density of 2103.4 mW/m2. X-ray photoelectron spectroscopy demonstrates the abundant existence of pyridinic nitrogen in ZIF-8 that meets the prerequisite for making an effective and efficient catalyst for ORR, and the carbon atoms adjacent to the pyridinic nitrogen are considered as the active sites with Lewis basicity. In addition, the graphitization of carbon in ZIF-8 enhanced the electronic conductivity and corrosion resistance during electrocatalysis. MFCs that use ZIF-8 as the catalyst can regularly work more than 110 h during a feeding period, which is considerably longer than that of the MFCs modified by Pt/C (approximately 40 h). The composite pore structure in ZIF-8 guarantees an rapid mass transfer rate on the three-phase boundary, which results in a faster ORR rate. These advantages make ZIF-8 a promising alternative catalyst for ORR of air-cathode MFC. Graphical abstract Image 1 Highlights • ZIF-8 exhibits an outstanding ORR performance in a neutral pH solution. • Operation time more than 110 h in a feed period. • Abundant active sites of ZIF-8 derived from micropores enhanced ORR activity. • Unique structural advantages guarantee a rapid mass transfer rate. • A maximum power density of 2103.4 mW/m2 was achieved by ZIF-8 modified MFC. [ABSTRACT FROM AUTHOR]

Abstract Developing highly efficient and economically sustainable electrocatalysts with bifunctions for the oxygen reduction reaction and oxygen evolution reaction is crucially important in practical implementation of rechargeable zinc-air batteries. Herein, a novel Cu-based electrocatalyst composed of Cu 97 P 3- x - y O x N y nanoparticles supported on N, P co-doped carbon is synthesized straightforward by the annealing of the Cu-phytic acid gel under an argon and ammonia gases atmosphere. The Cu 97 P 3- x-y O x N y /N, P co-doped carbon catalyst displays the outstanding catalytic performance for both the oxygen evolution reaction and oxygen reduction reaction in alkaline solution, which is ascribed to the synergistic effect of Cu 97 P 3- x-y O x N y and N, P co-doped carbon. Meanwhile, the primary and rechargeable zinc-air batteries assembled by the Cu 97 P 3 -x-y O x N y /N, P co-doped carbon catalyst exhibit a high specific capacity and remarkable charge-discharge cycle stability, which are comparable to that of the benchmark Pt/C and IrO 2. The energy density of the catalyst reaches to 737 Wh kg Zn −1. To the best of our knowledge, few Cu-based electrocatalysts is reported for rechargeable zinc-air batteries. Graphical abstract Image 1 Highlights • Cu 97 P 3- x-y O x N y /NPC was synthesized by annealing of the Cu-phytic acid gel. • Cu 97 P 3- x-y O x N y /NPC exhibited bifunctional catalytic activities toward ORR and OER. • Cu 97 P 3- x-y O x N y /NPC-based rechargeable zinc-air batteries exhibited high performance. • Highly catalytic performance attributes to the synergistic effect of each component. • Affording a new strategy for developing advanced multifunctional electrocatalyst. [ABSTRACT FROM AUTHOR]

Abstract The weak binding force of oxygenated species on metal-nitrogen-carbon catalytic sites severely restricts the catalytic activities towards the oxygen reduction reaction. Herein, we report a one-step method for the in-situ immobilization of poly(p -phenylenediamine-formaldehyde) on the Co, Zn-zeolitic imidazolate frameworks to construct pyrrolic/graphitic N-rich Co-N-C structures. Pyrrolic/graphitic N species derived from poly(p -phenylenediamine-formaldehyde) reduce the electron localization around the Co centers for increasing the charge polarization between Co and neighboring N atoms, leading to strengthening the adsorption of oxygenated species and improving the intrinsic activity. What's more, pyrrolic/graphitic N-rich Co-N-C structures conserve the characteristics of zeolitic imidazolate frameworks-derived catalysts, such as, large surface area, high pore volume, and atomically dispersed Co species, to fully expose efficient Co-N-C catalytic sites. Hence, the resultants as precious-metal-free catalysts demonstrate excellent catalytic activities in acidic and alkaline media, and are even superior to that of the state-of-the-art Pt/C catalyst in an alkaline environment. Moreover, doping S atoms into carbon lattice induces the asymmetric electron and spin densities of adjacent carbon atoms for providing for more oxygen adsorption sites and facilitating the formation of the OOH species, resulting in synergistically boosting the ORR activity in an acidic environment with efficient Co-N-C sites. Graphical abstract Image 1 Highlights • A facile one-step method is proposed to prepare the Co, Zn-ZIF/P p PDF complex. • P p PDF-derived N-doped carbon contains rich pyyrolic and graphitic N species. • Pyrrolic/graphitic N species weaken the electron localization around the Co centers. • The electron depletion strengthens the oxygen adsorption and ORR intrinsic activity. • The ORR activity in acidic media is improved with doping S species into the Co-N-C. [ABSTRACT FROM AUTHOR]

Abstract High-efficiency cathode catalysts are essential for microbial fuel cell development since they are one of the key components in chemical energy conversion in organic compounds into electricity. Here, novel Fe Mn bimetallic nanocatalysts are designed and hydrothermally synthesized for microbial fuel cells. Fe:Mn (atom%) = 1:4, 1:2, 1:1, and α-MnO 2 are applied in air-cathodes with Pt/C and activated carbon catalysts as benchmarks, and Fe Mn catalysts can enhance the performance. When Fe:Mn = 1:2, the FeMn 2 achieves a maximum power density of 1940 ± 31 mW m−2 in microbial fuel cells and a current density of 19.4 A m−2 at −0.056 V in abiotic electrochemical tests, 24% and 37% higher than Pt/C respectively. Material characteristics are systematically analyzed since they are directly related to the catalytic performance. The high catalytic activity of FeMn 2 proves to result from a combination of the weak Mn O bonds, large quantity of defects, large specific surface area and high Mn(III):Mn(IV) ratio, according to the proposed possible mechanisms of Fe Mn catalysts to enhance the output. This work not only puts forwards an easy-to-accomplish method to design and prepare bimetallic nanocatalysts, but also provides a potential alternative to Pt/C in microbial fuel cells for sustainable energy generation. Graphical abstract Image 1 Highlights • Fe Mn nanocatalysts were designed and prepared for MFC via hydrothermal method. • FeMn 2 air-cathode exhibited the highest MFC maximum power density of 1940 mW m−2. • The synergism of Fe3+ and α-MnO 2 lattice has been demonstrated. • The best performance of FeMn 2 was illustrated by proposed catalytic mechanisms. • The FeMn 2 outperformed commercial Pt/C and could be a potential alternative. [ABSTRACT FROM AUTHOR]

Abstract Novel cathode electrocatalysts based on Pd and cerium oxide nanorods (CeO 2-NR), supported on home-obtained graphene (G) and N-doped graphene (G D1, G D2), were synthesized. The electrocatalysts were identified as Pd CeO 2-NR /G, Pd CeO 2-NR /G D1 and Pd CeO 2-NR /G D2. In half cell measurements in 0.5 mol L−1 KOH, these electrocatalysts showed higher mass and specific activity for the Oxygen Reduction Reaction (ORR) than Vulcan-supported Pd/C and comparable to Pd CeO 2-NR /C. Tests in a dual-chamber Microbial Fuel Cell (MFC) were performed using pharmaceutical residual water (PRW) as anode substrate, while KOH (pH = 9.6) was the electrolyte in the cathode compartment. The bioanode was formed by commercial Pt/C electrocatalyst and Bacillus subtilis as the microorganism grown as a biofilm. Meanwhile, the gas diffusion electrode (GDE) cathode contained the above-mentioned Pd-based electrocatalysts. The MFC equipped with the Pd CeO 2-NR /G D1 electrocatalyst as cathode delivered an Open Circuit Voltage of 0.308 V and a maximum power density of 12.47 mW m−2. This performance was higher than those of the MFC with Pd/C (0.21 V and 4.50 mW m−2) and commercial Pt/C (0.21 V and 5.43 mW m−2) cathodes. Thus, Pd CeO 2-NR /G D1 is a promising cathode for MFCs. Moreover, B. subtilis demonstrated to be an active microorganism to generate electrical energy from PRW. Graphical abstract Image 1 Highlights • Application of cerium oxide nanorods (CeO 2-NR) as cathode co-catalyst. • CeO 2-NR and N-doped graphene enhance the performance of Pd for the ORR in KOH. • B. subtilis is an active microorganism to generate energy. • Pharmaceutical Residual Water is a suitable substrate for Microbial Fuel Cells. • Pd CeO 2-NR /G D1 cathode shows the higher performance in a Microbial Fuel Cell. [ABSTRACT FROM AUTHOR]

Abstract Nitrogen and fluorine co-doped hierarchical honeycomb-like carbon nanofibers (N F-CNFs-950) are prepared by electro-blown spinning technology and high temperature calcination. It possesses large specific surface area, micro/meso/macro hierarchical through-pore structure, high pyridine-N and graphite-N content. These characteristics make it exhibit an outstanding alkaline electrocatalytic oxygen reduction reaction (ORR) activity (half wave potential of 0.833 V vs reversible hydrogen electrode and current density of 5.48 mA cm−2). In particular, the introduction of the ionic C F/N F successfully avoids the inactivation of pyridine N in the carbon skeleton due to protonation in the acidic electrolyte. And the ionic C F/N F activated pyridine N work synergistically with graphite N to promote N F-CNFs-950 to exhibit an acidic ORR activity (half wave potential of 0.606 V vs reversible hydrogen electrode and current density of 5.58 mA cm−2) that is only second to commercial Pt/C. Importantly, the N F-CNFs-950 catalyst exhibits much better methanol tolerance and electrochemical stability in both alkaline and acidic environments. Graphical abstract Image 1 Highlights • Honeycomb-like N F-CNFs are prepared by EBS technology and carbonization. • Pyrolysis of PTFE provides greater specific surface area and porosity. • Optimized nitrogen and fluorine hybridization state of N F-CNFs are tuned. • N F-CNFs-950 exhibiting superior ORR performance in alkaline and acidic media. [ABSTRACT FROM AUTHOR]

Abstract Self-support silver nanofibers with excellent electrocatalytic performance for oxygen reduction reaction (ORR) are successfully fabricated through a hybrid method combining an electrospinning process with an electroplating technique. This nanofiber-based catalyst demonstrated superior long-term stability and an unusually high methanol-tolerant effect that its ORR activity was enhanced, instead of lessened in 3 M methanol. The impact of microstructure and crystal facet on ORR activity is examined through quantifying the performance of the catalysts by electrochemical measurements. Through tuning the synthesis parameters, the onset potential, half-wave potential, and peak potential of 1.041 V, 0.848 V, and 0.864 V are achieved for the silver nanofibers with thorny structure, even superior to those of commercial Pt/C catalyst. Such excellent performance is attributed to two major factors, the micro morphology, i.e. thorn-on-fiber structure, and the crystal facet. The special thorny structure leads to the accumulation of electrons on the tip to act as highly active sites and better confinement of the oxygen between thorns, while the high ratio of (110) facets on the tip favors high catalytic activity. This kind of low-cost silver nanofiber-based catalyst exhibits a highly beneficial prospect as a potential alternative catalyst for oxygen reduction reaction. Graphical abstract Image 1 Highlights • Supportless AgNFs with thorny structures were synthesized. • The best ORR activity among the reported Ag-based catalysts. • Superior long-term stability and an unusual methanol response. • Electron enrichment and high (110) facet exposure appear at thorny tips. • Their synergetic roles greatly contribute to high ORR activity. [ABSTRACT FROM AUTHOR]

Abstract Nanostructuring of electrocatalysts is an important aspect of catalyst design as catalytic performance depends not only on the specific activity (reaction rate per surface area), but also on the dispersion of the catalyst. We present an industrially compatible, but effective preparation method for support-free nanostructured catalyst layers. Alternating sputtering was used to prepare heterogeneous Pt Cu templates ranging from 95 up to 99.5 at. % Cu. These templates were then electrochemically leached to form a nanostructured Pt Cu network and benchmarked with respect to the oxygen reduction reaction. It is shown that the templates with lower Cu:Pt ratios exhibit the highest initial specific activity but have a relatively low electrochemically active surface area. Subjecting the samples to extended accelerated stress tests, it is found that the support-free nanostructured Pt Cu networks are relatively resistant to high potential cycling, which can be explained by the lack of carbon corrosion. The loss in electrochemical surface area thereby depends on the initial Pt content. The specific oxygen reduction activity, however, approaches the value of bulk Pt. Although this decrease is not desirable, still an (specific) activity improvement of two to four times as compared carbon supported nanoparticles can be preserved. Graphical abstract Image 1 Highlights • Novel industrially scalable ORR electrode production method demonstrated. • Porous nanostructured material with a specific surface area up to 47 m2 g−1 Pt. • Specific activity at 0.9 V RHE up to 5.8 mA cm−2 Pt and mass activity up to 1.9 A mg−1 Pt. • Remaining Cu has positive effect on specific activity. • Electrochemical active surface area depends on as-deposited Cu content. [ABSTRACT FROM AUTHOR]

Abstract Protonic ceramic fuel cells offer the potential for environmentally sustainable and cost-effective electric power generation. However, the power outputs of protonic ceramic fuel cells are far from the requirements due to the lack of active cathodes. In this work, porous thin sheets Ca x Y 1-x Fe 0.5 Co 0.5 O 3- δ (x = 0.1, 0.3 and 0.5) are synthesized by a modified pechini method and investigated as cathode materials for protonic ceramic fuel cells. Ca x Y 1-x Fe 0.5 Co 0.5 O 3- δ show high electrical conductivities and excellent chemical compatibility with Ba(Zr 0.1 Ce 0.7 Y 0.2)O 3 electrolyte. The maximum electrical conductivity of Ca 0.3 Y 0.7 Fe 0.5 Co 0.5 O 3- δ reaches 202 S cm−1 in air at 750 °C. The detailed mechanism for oxygen reduction reaction reveals that the rate-limiting step of oxygen reduction reaction is transformed from charge transfer to O 2 adsorption-dissociation with temperature rising or Ca doping. The composite cathode Ca 0.3 Y 0.7 Fe 0.5 Co 0.5 O 3- δ -Ba(Zr 0.1 Ce 0.7 Y 0.2)O 3 presents a relatively low polarization resistance of 0.07 Ω cm2 at 750 °C in air. The power density of the anode-supported cell of NiO Ba(Zr 0.1 Ce 0.7 Y 0.2)O 3 ∣Ba(Zr 0.1 Ce 0.7 Y 0.2)O 3 ∣Ca 0.3 Y 0.7 Fe 0.5 Co 0.5 O 3- δ-Ba(Zr 0.1 Ce 0.7 Y 0.2)O 3 is 798 mW cm−2 as the electrolyte thickness is about 150 μm. The prepared Ca x Y 1-x Fe 0.5 Co 0.5 O 3- δ oxides are promising candidates as high-performance cathodes for protonic ceramic fuel cells. Graphical abstract Image 1 Highlights • Increasing proper Ca doping at A -site is improving the conductivity of CYFC. • The detailed mechanism for oxygen reduction reaction is analyzed. • The R p of composite cathode C3YFC-BZCY was 0.07 Ω cm2 in air at 750 °C. • The peak power density is 798 mW cm−2 at 750 °C as the thickness of BZCY is 150 μm. [ABSTRACT FROM AUTHOR]

Abstract Perovskite LaMnO 3 is reported to be a superior electrocatalyst for oxygen reduction reaction in terms of the onset potential and intrinsic activity. However, traditionally prepared LaMnO 3 is characterized to exhibit a low specific surface area and a limited pore volume. Herein, we synthesize a three-dimensional ordered macroporous LaMnO 3 that features ordered and interconnected porous structure, in order to increase catalytic sites. The obtained three-dimensional ordered macroporous LaMnO 3 exhibits an increased specific surface area of 20.328 m2 g−1 and pore volume of 0.126 cm3 g−1. Rotating-ring-disk electrode measurement reveals a more positive onset potential (0.827 V) and half-wave potential (0.686 V), and a much higher current-limited density (5.90 mA cm−2) of the three-dimensional ordered macroporous LaMnO 3 compared to counterparts, as well as a high electron transfer number (∼4) and a better stability. Furthermore, a Li O 2 battery employing the three-dimensional ordered macroporous LaMnO 3 as air electrode exhibits excellent electrochemical performance with a higher initial discharge capacity (5592 mAh g−1), a smaller discharge-charge voltage gap (1.56 V), and a higher coulombic efficiency (∼100%) in comparison with the carbon electrode. Our results suggest that traditional perovskite oxides could be effectively optimized for efficient electrocatalytic reactions. Graphical abstract Image 1 Highlights • A three-dimensionally ordered macroporous perovskite LaMnO 3 is prepared. • Increased specific surface area and pore volume of LaMnO 3 are obtained. • The ordered porous structure is beneficial for oxygen reduction reaction. • A battery employing optimized LaMnO 3 exhibits excellent performance. [ABSTRACT FROM AUTHOR]

Abstract Rational design of high-efficiency and cost-effective nonprecious metal-based catalysts with outstanding oxygen reduction reaction (ORR) performance, is of great importance to replace platinum-based electrocatalysts in fuel cell. Herein, a novel N, B and Fe co-doped carbon materials (Fe-NBC) electrocatalyst is designed through the pyrolysis of a metal-organic coordination polymer precursor, which is formed from the coordination between dendrimer-like terpyridinic monomer and Fe3+. The as-prepared Fe-NBC catalyst exhibits superior ORR activity with an onset potential of 0.98 V and a half-wave potential of 0.86 V, which are comparable to that of the Pt/C catalyst. The formation of Fe-N x moieties is considered to be the most important factor for the improved ORR activity of Fe-NBC. Besides, Fe-NBC catalyst displays a better methanol tolerance as well as durability (5 mV negative shift of E 1/2 , after 1000 cycles) in comparison with Pt/C (12 mV negative shift of E 1/2 , after 1000 cycles). This work provides a facile protocol for the design and fabrication of multi-element co-doped carbon materials. Moreover, the excellent ORR performance of these N, B and Fe co-doped carbon materials may be a potential candidate to replace Pt-based catalyst in fuel cells. Graphical abstract Image 1 Highlights • A supramolecular polymer comprising N, B and Fe elements was designed. • The effect of Fe-N x content and boron element on ORR performance was studied. • High activity, good methanol tolerance and durability for ORR were achieved. [ABSTRACT FROM AUTHOR]

Abstract The role of porosity, and more specifically, microporosity, in the performance of carbon materials as Oxygen Reduction Reaction (ORR) catalysts in alkaline medium still has to be clarified. For this purpose, a highly microporous KOH-activated carbon and a microporous char have been prepared and their ORR performance in alkaline media were compared to that of two commercial carbon blacks with low and high surface areas, respectively. Interestingly, all carbon materials show a two-wave electrocatalytic process, where the limiting current and the number of electron transferred increase when going to more negative potentials. The limiting current and onset potential of the second wave is positively related to the amount of microporosity, and H 2 O 2 electrochemical reduction tests have confirmed that the second wave could be related to the catalytic activity towards this reaction. In accordance to these findings, a model is developed that takes into account narrow and wide micropores in both charge transfer reactions and the mass transfer rate of O 2 and H 2 O 2. This model successfully reproduces the experimental electrochemical response during ORR of the analyzed porous carbon materials and suggests the important role of narrow micropores in H 2 O 2 reduction. Graphical abstract Image 1 Highlights • Activity of porous carbons in ORR is undoubtedly related to their porosity. • ORR occurs through O 2 reduction to HO 2 − and then HO 2 − reduction to OH−. • Microporosity is correlated to a high activity of both O 2 and HO 2 − reductions. • Narrow micropores have higher activity to HO 2 − reduction. [ABSTRACT FROM AUTHOR]

Abstract Two kinds of ternary cobalt gold palladium (CoAuPd) and three kinds of binary AuPd alloy nanocatalysts are synthesized by co-reduction and successive reduction method. The CoAuPd nanocatalysts obtained by the successive reduction method possess a hollow structure with some solid nanospheres, nanodendrites and show much better catalytic activity for methanol oxidation reaction (MOR) (1.26 mA cm−2) than another CoAuPd NCs (1.14 mA cm−2) and binary AuPd nanocatalysts (0.85 mA cm−2). CO adsorption and electrochemical dealloying method can restructure nanocatalyst surface and improve MOR and oxygen reduction reaction (ORR) activities. Electrochemical dealloying reconstructs the hollow CoAuPd alloy to a CoAuPd@AuPd core-shell structure with pinholes and the dealloyed NCs exhibits better MOR (1.92 mA cm−2) and ORR (6.3 mA cm GEO −2) catalytic activities than the initial CoAuPd nanocatalysts (1.26 mA cm−2 for MOR and 3.4 mAcm GEO −2 for ORR). Accelerated durability tests (ADT) quantify the changes of stability before and after the surface reconstruction. The ternary CoAuPd nanocatalysts have excellent durability before and after surface reconstruction (current density decrease 14.04% for MOR and 0.3 mA cm GEO −2 for ORR) in alkaline medium. Highlights • Hollow CoAuPd nanocatalysts are synthesized using a successive reduction method. • Electrochemical dealloying and CO-stripping are applied to reconstruct the surface texture. • Dealloyed CoAuPd nanocatalysts exhibit enhanced catalytic activity for MOR and ORR. [ABSTRACT FROM AUTHOR]

Abstract Iron and nitrogen co-doped carbons show great potential for high-performance electrochemical oxygen reduction reaction. However, the rational design of atomically dispersed iron over nitrogen-doped carbons with activity comparable to that of Pt-C is still challenging. Herein, we develop a new approach that enables the direct formation of intrinsically nitrogen-functionalized two-dimensional sheet-like carbons containing a high concentration of single Fe atoms. This strategy only involves one-step pyrolysis of both, guanine and iron nitrate, without using any guiding agent and sacrificial template. The electrochemistry tests demonstrate an excellent ORR performance of the prepared Fe-N x -C catalyst with a half-wave potential of 0.85 V and a limited current density of −6.5 mA/cm2 in alkaline medium, outperforming the commercial Pt-C and most of previously reported Fe-N x -C catalysts. We believe that the emergence of superior ORR performance is mostly attributed to the uniform dispersion of single Fe atoms at the molecular level and the formation of abundant coordinated Fe-N x sites. In addition, the high surface area, optimal porosity and defective structure (particularly the defects at the edge) of the two-dimensional carbons are also beneficial for the improved ORR activity. Graphical abstract Image 1 Highlights • Nitrogen-doped carbon nanosheets are synthesized by in-situ pyrolysis of biomolecule. • The 2D carbons allow the deposition of highly dispersed single iron atoms. • The prepared Fe-N x -C exhibits outstanding ORR activity. • The coordinated Fe-Nx sites play a key role in the catalysis for ORR. [ABSTRACT FROM AUTHOR]

Abstract The exploration of cheap and stable electrocatalysts with high activity towards oxygen reduction reaction in the acidic and alkaline medium is a vital activity for large-scale applications of fuel cells. In recent years, one-dimensional nanofibrous electrode materials with high surface area and specific porosities have been drawing great attention in energy conversion devices such as fuel cells and metal-air batteries. Nanofibers with a one-dimensional nanostructure can be produced by electrospinning, which has been considered as a particularly low-cost and versatile method. In this review, we summarize the properties of electrospun nanofibers and the recent progress in designing of non-precious nanostructured electrocatalysts for oxygen reduction reaction in fuel cells. More importantly, we also highlight the interesting nanostructures, new synthetic approaches, and the electrocatalytic performance including active sites and stability of electrospun-based electrocatalysts. In addition, we describe the research challenges and future developmental perspectives of electrospun materials in energy technology. Highlights • Non-precious nanostructured electrocatalysts by electrospinning are summarized. • The active sites and reaction mechanism of the electrocatalysts are discussed. • Research challenges and future perspectives are described. [ABSTRACT FROM AUTHOR]

Abstract A highly active electrocatalyst is synthesized by employing melamine assisted metal-organic framework as the precursor. By pyrolyzing the hybrid at 350–800 °C, the precursor can be easily transferred into abundant iron and nitrogen co-doped carbon skeleton. The microbial fuel cell doped with the above treated sample at 600 °C achieves the maximum power density 2229 ± 10 mW m−2, 257% and 36.6% higher than that of activated carbon and the control sample. The total resistance decreases by 53.8% from 18.16 Ω (activated carbon) to 8.39 Ω. The reaction process is testified to be four-electron transfer. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy prove the coexistence of divalent copper and C 3 N 4 and the incorporation of nitrogen into the network formed active sites. Thus, the ideal results make the pyrolyzed hybrid at 600 °C a promising catalyst in microbial fuel cell. Highlights • Cu-MOF as precursor avoid agglomeration between laden active components. • The bonds between Cu and nitrogen greatly accelerated catalytic reaction rate. • The high mesoporous volume of C 3 N 4 -Cu-MOF600 improved the ORR in MFC. • The MPD was 2229 ± 10 mW m−2, higher than that of AC electrode. [ABSTRACT FROM AUTHOR]

Abstract A chemically controlled facile approach is developed for the in-situ growth of Co 3 O 4 microspheres on N,S-co-doped rGO sheets (Co 3 O 4 /N,S-rGO) employing thiamine hydrochloride (THCl) (7.41 mM) as the N and S co-doping agent under mild experimental conditions. The THCl concentration plays a vital role in controlling the growth of cobalt crystals anchored on the surface of N,S-rGO. The change in concentration of THCl from 7.41 to 22.20 mM alters the deposition of cobalt crystal on the N,S-rGO surface from Co 3 O 4 to Co 9 S 8 (Co 9 S 8 /N,S-rGO). This change is understood due to the formation of different intermediate complex structure driven by supramolecular interactions. The altered cobalt crystal phase leads to tuned morphologies, surface areas and catalytically active centers which are investigated by various characterization techniques. Co 3 O 4 /N,S-rGO exhibits superior electrocatalytic activity for oxygen reduction reaction (ORR) compared to Co 9 S 8 /N,S-rGO. Moreover, Co 3 O 4 /N,S-rGO shows more positive onset potential (0.90 V vs. RHE), half-wave potential (0.74 V vs. RHE), relatively high limiting current density and smaller Tafel slope (52 mV per decade) compared to its separate components owing to synergistic effects. Co 3 O 4 /N,S-rGO hybrid also outperforms the electrocatalytic activity of commercial Pt/C in terms of durability and methanol tolerance under alkaline conditions. Graphical abstract Image 1 Highlights • A facile synthesis of Co 3 O 4 /N,S-rGO was achieved by using thiamine hydrochloride. • Thiamine hydrochloride controlled the growth and phase of cobalt crystal on N,S-rGO. • ORR activity of Co 3 O 4 /N,S-rGO hybrid was enhanced due to synergistic effect. • Active sites and electroactive surface area were found to be vital for improved ORR. • Co 3 O 4 /N,S-rGO hybrid showed better durability and methanol tolerance than Pt/C. [ABSTRACT FROM AUTHOR]

Abstract The shape-tunable Pt Cu Ni rhombic dodecahedra nanoframe is achieved via modified solvothermal and two-step etching, the first step is Pt Cu Ni concave rhombic dodecahedra synthetized due to oxidation etching, and the second step is Pt Cu Ni nanoframes obtained through the acid etching. The Pt Cu Ni solid rhombic dodecahedra as an intermediate product can be well controlled by adjusting the amount of reaction time and Ni precursor. Based on the formation mechanism of Pt Cu nanoframes, the morphological evolution process of ternary nanoframe is precisely investigated according to the changes of morphology, atomic ratio and average particle size. In addition, shape-tunable Pt Cu Ni nanoframes catalyst shows enhanced mass activity of 0.86 A mg−1Pt at 0.9 V versus reversible hydrogen electrode towards oxygen reduction reaction, which is 6 times as well as that of the commercial Pt/C catalyst. Remarkably, there is a more positive onset potential of Pt Cu Ni nanoframes compared to other catalysts. More importantly, this synthetic method opens a promising door towards development and applications of Pt based catalysts. Graphical abstract Image 1 Highlights • Pt Cu Ni nanoframes with highly open structures and high atomic utilization are synthesized. • A modified solvothermal and two-step etching method is used to make shape-tunable catalyst. • The growth mechanism of Pt Cu Ni nanoframes is significantly investigated. • Pt Cu Ni catalyst shows 6 times mass activity for ORR than that of the Pt/C catalyst. [ABSTRACT FROM AUTHOR]

Abstract PtNi/C octahedral nanocrystal catalyst is prepared through surfactant-assisted solvothermal approach using cetyltrimethylammonium bromide as structure directing agent, and its performance on rotating disk electrode and membrane electrode assembly are investigated through experiment and simulation. Its mass activity and specific activity at 0.9 V vs. RHE are about 6.1 and 6.6 times high of commercial Pt/C, respectively. The membrane electrode assembly that is fabricated using PtNi/C octahedral catalyst in cathode exhibits enhanced power generation performance and durability. Its cell voltage at 1000 mA cm−2 is increased by 34 mV compared with the control, and its maximum power densities are raised by 160.2 mW cm−2 and 0.27 kW g Pt −1. After 100 h galvanostatic durability test, the attenuation rates of its cell voltage at 1000 mA cm−2 and maximum power density are 6.9% and 14.3% (10.9% and 18.4% for the control), respectively. The simulation results also reveal that PtNi/C octahedral catalyst not only has high half cell performance, but also shows actual application potential in single cell, which demonstrates the feasibility that the excellent performance of PtNi/C octahedral catalyst at rotating disk electrode level can be realized in single cells through optimization of membrane electrode assembly fabrication and cell operation conditions. Graphical abstract Image 1 Highlights • PtNi/C octahedral catalyst was prepared with CTAB as structure directing agent. • Effect of CTAB concentrations on nanocrystal morphology was investigated. • The research gaps on single cell application of octahedral catalyst were made up. • Both experiment and simulation were employed to investigate its performance. • PtNi/C octahedral catalyst shows enhanced half cell and single cell performance. [ABSTRACT FROM AUTHOR]

Abstract To improve the sluggish oxygen reduction reaction from the cathode of solid oxide fuel cells (SOFCs), a conformal layer of catalytic CoO x grains was deposited onto the internal surface of LSM/YSZ composite cathode of commercial cells, through atomic layer deposition (ALD). Upon the electrochemical operation, the ALD coated cell has dramatic reduction of the polarization resistance, and the power density exhibits continuous increase over the course of 172 h operation at 750 °C and reaches the cell performance enhancement by a factor of 1.6, in comparison with that from the baseline operated for 96 h. Such performance enhancement was attributed to the combination of the newly added triple phase boundaries for promoting the oxygen reduction reaction, as well as the accelerated oxygen transport on the cathode surface. The present work opens the further research direction for ALD coating of non-precious metal catalyst to boost the performance of as-fabricated SOFCs. Highlights • Conformal CoO x layer is deposited on LSM/YSZ backbone of SOFC cathode using ALD. • CoO x ALD layer continuously improves the oxygen reduction reaction upon operation. • CoO x ALD layer interacts with the backbone and formed catalytic Co 0.7 Mn 0.3 O x. • Co 0.7 Mn 0.3 O x exhibits Bi-model distribution on LSM and YSZ surfaces. [ABSTRACT FROM AUTHOR]

Abstract The Ag 4 Sn and Ag 3 Sn intermetallics are successfully synthesized by combining electrochemical deposition and dealloying methods. The Ag 4 Sn and Ag 3 Sn possess a half-wave potential of 0.810 mV and 0.790 mV respectively for the oxygen reduction reaction in alkaline media, which are comparable to the commercial Pt/C (0.837 mV). In term of the durability, the Ag 4 Sn retains a half-wave potential of 0.775 mV after 5000 potential cycles, which is superior to Pt/C of 0.784 mV. The better catalytic activity and durability are mainly attributed to the ensemble effect and strong chemical bond in the AgSn ordered intermetallic structure. The catalytic activity is hardly influenced by methanol or ethanol in alkaline media with alcohol concentrations up to 1.0 M. Therefore, a membraneless alkaline zinc-air battery and direct alcohol fuel cell can operate with Ag 4 Sn and Ag 3 Sn intermetallics as the cathode catalysts, which allow the anode fuel to freely enter the cathode. A high power density is delivered by the membraneless alkaline fuel cells with zinc, methanol or ethanol as anode fuels. The excellent alcohol-tolerance is beneficial to the oxygen reduction reaction of alkaline fuel cells and makes the AgSn intermetallics a promising candidate to replace Pt-based electrocatalysts for oxygen reduction reaction. Highlights • AgSn intermetallics were successfully synthesized by an electrochemical method. • AgSn intermetallics exhibited excellent ORR activity and stability. • AgSn intermetallics showed superior tolerance to alcohol than commercial Pt/C. • High catalytic properties are attributed to ensemble effect and ordered structure. • Membraneless alkaline fuel cells based on selective catalysts were designed. [ABSTRACT FROM AUTHOR]

Abstract Nitrogen-doped mesoporous carbons containing a small amount of Fe (Fe-N-MC) are prepared from a low-cost carbon source (agarose) together with nitrogen and iron precursors. The synthesis consists in the formation of a hydrogel embedding FeCl 2 or tris(1,10-phenanthroline)iron(II)dichloride (Fe(Phen) 3 Cl 2), which after a freeze-drying treatment, is pyrolyzed at 400 °C to give a crude product, which is further graphitized at high temperature. The formation of a hydrogel assures an optimal Fe dispersion and an optimal surface area and pore network after pyrolysis, as evaluated by N 2 adsorption-desorption isotherms. The final product is further activated by treatment in KOH at 750 °C or in H 2 SO 4 at 100 °C followed by H 2 reduction at 700 °C. Both treatments allow to increase the surface area and pore volume, and to expose Fe-N x active sites, as confirmed by both XPS and Mössbauer spectroscopies. The Fe-N-MC catalytic performances towards oxygen reduction reaction are investigated by electrochemical techniques in 0.1 M HClO 4 , attesting that O 2 is reduced following an almost 4e− pathway at very positive potentials (0.8 V vs RHE). The effect most influencing the catalytic activity is found to be the employment of Fe(Phen) 3 Cl 2 instead of FeCl 2 +1,10-phenanthroline for the generation of Fe-N x active sites. Graphical abstract Image 1 Highlights • Fe-N-C catalysts were synthetized from agarose dry hydrogel and Fe(Phen) 3 Cl 2. • The employment of a gel allowed a very homogeneous dispersion of the precursors. • Fe-N x and Fe 3 C active sites were determined by both XPS and Mössbauer analyses. • Fe-N-C900C showed high mass activity and E 1/2 and a quasi -four-electron ORR process. [ABSTRACT FROM AUTHOR]