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Novel Fe N C electrocatalysts derived from conjugated microporous polymers based on pre-functionalization of monomers was developed, which exhibits great potential for cathodic oxygen reduction reaction in fuel cell and provides a feasible strategy of developing multi-atoms doping catalysts for heterogeneous catalysis. [Display omitted] Porous iron–nitrogen-doped carbons (Fe N C) offer a great platform for construction of cathodic oxygen reduction reaction (ORR) catalysts in fuel cells. However, challenges still remain regarding with the collapse of carbon-skeleton during pyrolysis, uneven distribution of active sites and aggregation of metal atoms. In this work, we synthesized Fe, N co-doped conjugated microporous polymer (FeN-CMP) through a facile bottom-up strategy using 1,3,5-triethynylbenzene and iron-chelated 3,8-dibromo-1,10-phenanthroline as monomers, ensuring the uniform coordination of N with Fe element in network. Then, the resulting FeN-CMP was treated by pyrolysis without structural collapse to obtain porous Fe N C electrocatalyst for ORR. The most active catalyst was fabricated under 900 °C, which exhibits remarkable ORR activity in alkaline medium with half-wave potential of 0.796 V (18 mV and 105 mV positive deviation from the commercial Pt/C catalyst and post-doping catalyst), high selectivity with nearly 4e- transfer process and excellent methanol tolerance. Our study first developed porous Fe N C electrocatalysts derived from Fe, N -anchoring CMPs based on pre-functionalization of monomers, which exhibits great potential as an alternative to commercial Pt/C catalyst for ORR, and provides a feasible strategy of developing multi-atoms doping catalysts for energy storage and conversion as well as heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

Coordination environment engineering is developed to synthesize Fe SA /NSC catalysts with the tailored N, S co-coordinated Fe atomic site. [Display omitted] • The Fe-N 3 S active site with the optimized electronic structure is constructed. • S doping promotes the OH* desorption, thus leading to enhanced kinetics process. • The catalyst displays impressive ORR activity in both alkaline and acidic mediums. • The catalyst exhibits excellent performance in Zn-air batteries and fuel cells. Atomically dispersed iron–nitrogen-carbon (FesbndNsbndC) materials have been considered ideal catalysts for the oxygen reduction. Unfortunately, designing and adjusting the electronic structure of single-atom Fe sites to boost the kinetics and activity still faces grand challenges. In this work, the coordination environment engineering is developed to synthesize the Fe SA /NSC catalyst with the tailored N, S co-coordinated Fe atomic site (Fe-N 3 S site). The structural characterizations and theoretical calculations demonstrate that the incorporation of sulfur can optimize the charge distribution of Fe atoms to weaken the adsorption of OH* and facilitate the desorption of OH*, thus leading to enhanced kinetics process and intrinsic activity. As a result, the S-modified Fe SA /NSC exhibits outstanding catalytic activity with the half-wave potentials (E 1/2) of 0.915 V and 0.797 V, as well as good stability, in alkaline and acidic electrolytes, respectively. Impressively, the excellent performance of Fe SA /NSC is further confirmed in Zn-air batteries (ZABs) and fuel cells, with high peak power densities (146 mW cm−2 and 0.259 W cm−2). [ABSTRACT FROM AUTHOR]

A novel strategy to prepare COF-derived carbon materials mediated by volatile guest molecule for efficient electrocatalytic oxygen reduction reaction is reported. [Display omitted] Covalent organic framework (COF) derived metal-free carbon materials have emerged as promising electrocatalysts for the oxygen reduction reaction (ORR). Herein, a volatile guest molecule mediated-pyrolysis strategy was explored on a designed thiophene-rich and imine-linked COF. Through the modulation of guest mediators (iodine and sulfur), the properties of the as-obtained carbon materials can be well regulated. The optimized nitrogen and sulfur dual-doped carbon electrocatalyst demonstrates remarkable ORR activity with a half-wave potential of 0.87 V and impressive durability, with only an 8% current loss over 21 h. The corresponding assembled zinc-air battery has a comparable power density (60 mW cm−2) to that of the commercial Pt/C. It is proposed that the coexistence of the guest mediators iodine and sulfur in the channels of COFs could prevent the loss of N species. The enhanced N content and N/S ratio are assumed to be responsible for the ORR performance. This study puts forward a novel strategy to prepare COF-derived carbon materials mediated by volatile guest molecules, which may provide new insights into the development of metal-free ORR catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] Oxygen reduction reaction (ORR) is an essential half-reaction in next-generation energy storage and conversion systems, such as metal-air batteries and fuel cells. However, its practical application is restricted by the slow intrinsic kinetics, and the high price and low storage of noble metal electrocatalysts. Herein, unique CoFe nanoparticles encapsulated in N -doped carbon (CoFe-NC-Z8-900) with high content graphite-N derived from CoFe-g-C 3 N 4 @ZIF-8 via stepwise pyrolysis is reported as effective ORR catalysts. The increase of graphitic nitrogen content can enhance both the electrical conductivity and the adsorption of oxygen-containing intermediates, resulting in improved catalytic performance. Fortunately, CoFe-NC-Z8-900 exhibits an exceptionally high half-wave potential (E 1/2) of 0.914 V in a 0.1 M KOH solution. The excellent ORR electrocatalytic activity can be mainly attributed to the synergistic effect of the CoFe bimetal and the relatively high content of graphite-N. This study offers a unique method for creating powerful nitrogen-doped carbon coated metal nanoparticle electrocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] In this study, we present a bimetallic ion coexistence encapsulation strategy employing hexadecyl trimethyl ammonium bromide (CTAB) as a mediator to anchor cobalt–nickel (CoNi) bimetals in nitrogen-doped porous carbon cubic nanoboxes (CoNi@NC). The fully encapsulated and uniformly dispersed CoNi nanoparticles with the improved density of active sites help to accelerate the oxygen reduction reaction (ORR) kinetics and provide an efficient charge/mass transport environment. Zinc-air battery (ZAB) equipped CoNi@NC as cathode exhibits an open-circuit voltage of 1.45 V, a specific capacity of 870.0 mAh g−1, and a power density of 168.8 mW cm−2. Moreover, the two CoNi@NC-based ZABs in series display a stable discharge specific capacity of 783.0 mAh g−1, as well as a large peak power density of 387.9 mW cm−2. This work provides an effective way to tune the dispersion of nanoparticles to boost active sites in nitrogen-doped carbon structure, and enhance the ORR activity of bimetallic catalysts. [ABSTRACT FROM AUTHOR]

N -doped porous carbon monatomic iron catalysts (Fe SA /NPCs) obtained by polydopamine modification strategy were used for high efficiency oxygen reduction reactions and zinc-air batteries. [Display omitted] • Nitrogen doped porous carbon materials (NPCs) were prepared based on ZIF-L. • Stable hollow leaf-like morphology was maintained by coating PDA and nitrogen content was adjusted. • Fe SA was easily anchored on NPCs with luxuriant anchoring sites. • Fe SA /NPCs shows excellent electrochemical performance in oxygen reduction and zinc air batteries. Metal-nitrogen-carbon (M N C) catalysts, especially Fe N C catalysts, are considered promising candidates to replace Pt-based catalysts, but Fe N C catalysts still present certain challenges in controlled-synthesis and energy device applications. In this paper, through the modification strategy of poly-dopamine (PDA) to maintain 2D leaf morphology to obtain more active sites and further adjust the N content, N -doped porous carbon monatomic iron catalyst (Fe SA /NPCs) with rich-nitrogen content was prepared. XPS analysis showed that compared with C-ZIF-Fe, the contents of graphite nitrogen and pyridine nitrogen increased in Fe SA /NPCs. The hollow structure with defects and Fe-N 4 configuration of Fe single atom show more active sites for the catalyst, and positively promote the diffusion of reactants, oxygen exchange and electron transport, thus changing the reaction kinetics and promoting the improvement of ORR activity. Fe SA /NPCs electrocatalyst exhibits good half-wave potential and onset potential at low loading (E 1/2 = 0.93 V, E onset = 1.0 V). In addition, the methanol tolerance, stability and Tafel slope are better than those of commercial Pt/C. Excitingly, the zinc-air cell with Fe SA /NPCs as cathode material achieves a power density of 223 mW cm−2 and exhibits a long-term stability higher than 200 h. This work shows that nitrogen-doped porous carbon materials as well as iron monoatoms play important roles in improving electrocatalytic performance. [ABSTRACT FROM AUTHOR]

Cathodic oxygen reduction reaction is a decisive factor for fuel cell. In this work, for the first time, we demonstrated the synthesis of N -doped carbon hollow spheres derived from conjugated microporous polymers. The resulting sample remained the inherent porosity and N component with hollow spherical morphology, which exhibits excellent ORR performance with higher limiting current density and stability than that of commercial Pt/C catalyst in alkaline solution. [Display omitted] The exploitation non-precious or metal-free electrocatalysts of oxygen reduction reaction (ORR) is of significance for construction of next-generation fuel cells. In this work, hollow-spherical conjugated microporous polymers (CMPs) comprising porphyrin units were synthesized as precursors to prepare N -doping porous carbon spheres (CMP-NP-x) by a direct pyrolysis method. The as-resulted CMP-NP-x exhibited spherical morphology with hollow structure similar to that of CMPs precursors. The BET surface area of CMP-NP-x can be tailored by the pyrolysis temperature varying from 868 m2 g−1 to 1118 m2 g−1. According to XPS analysis, the pyrrolic N content in the sample decreased but the graphitic N and pyridinic N increased with increasing of the pyrolysis temperature from 800 °C to 1000 °C. Taking advantages of porous structure with large accessible surface areas and N species active sites, the resulting CMP-NP-x showed superior ORR activity and methanol tolerance to commercial Pt/C catalyst. In particular, CMP-NP-900 possesses the highest onset potential (0.930 V), half-wave potential (0.857 V) and limiting current density of 4.45 mA cm−2, compared with Pt/C catalyst and other samples, making it a promising metal-free catalyst superior to commercial Pt/C catalyst in alkalic condition. [ABSTRACT FROM AUTHOR]

[Display omitted] Nitrogen- and transition metal-dual doped carbon materials with low cost and high catalytic performances are considered as one of promising alternatives for noble metal catalysts in acceleration of oxygen reduction reaction (ORR). In this work, three-dimensional (3D) self-supporting superstructures of iron carbide (Fe 3 C) nanoclusters entrapped in manganese (Mn)- and nitrogen (N)-dual doped carbon nanosheets covered with double-sided nanoneedles carbon arrays (Fe 3 C/Mn,N-NCAs) are simply synthesized by a coordination pyrolysis method, in which dicyandiamide mainly behaves as nitrogen source and 1-(2-pyridylazo)-2-naphthol (PAN) as carbon source. Integration of the unique 3D self-supporting superstructures and synergistic effects of the multi-compositions, the as-obtained catalyst displays appealing ORR performance such as the much positive onset potential (E onset = 0.98 V vs. RHE) and half-wave potential (E 1/2 = 0.88 V vs. RHE), as well as a just 10 mV negative shift in E 1/2 after 2000 cycles, surpassing commercial Pt/C. This work provides some valuable perspectives for preparation of high-efficiency and low-cost non-noble metal ORR electrocatalysts in energy transformation and storage correlated systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synergistic effect of carbon edges and dopants towards ORR was predicted by DFT. • Well-designed N -GNRs contain both heteroatom-doping and abundant edge sites. • Best ORR property was obtained for N -GNRs compared to other control samples. • The synergistic effect was again demonstrated by experimental facts. Decoration with alien atoms and increasing the edge content are two valid ways to activate the oxygen reduction reaction (ORR) property of nanocarbons. To further enhance their intrinsic activity and explore the underlying ORR mechanism, graphene nanoribbons (GNRs) were selected as an ideal catalyst model. Theoretical simulations have predicted that with the synergistic effect between heteroatom-doping and edge sites, the ORR activity can be significantly improved. Inspired by this, N -GNRs were synthesized via the oxidative unzipping of CNTs followed by nitrogen incorporation with urea. Ample edges and nitrogen doping sites were detected by high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy, respectively. As a result, N -GNRs exhibited remarkably higher ORR properties in terms of onset and half-wave potentials, Tafel slopes, electron transfer number and methanol tolerance than either GNRs, the control sample without doping, or N -CNTs, the control sample without abundant edges, simply clarifying the significance of synergy between dopants and edges. Thus, this work provides a simple but efficient strategy to fabricate high-performance oxygen reduction catalysts. [ABSTRACT FROM AUTHOR]

A template-free pyrolysis approach is proposed to fabricate nitrogen and sulfur doped hollow mesoporous carbon sphere (N/S-HMCS). The unique hollow/mesoporous nanostructure and abundant N, S-doped active sites prompt the optimal N/S-HMCS 900 exhibits satisfactory electrocatalysis in oxygen electroreduction for high-performance Zn-air battery. [Display omitted] • A nitrogen, sulfur dual-doped hollow mesoporous carbon sphere (N/S-HMCS) is fabricated by a simple yet efficient template-free pyrolysis approach. • The N/S-HMCS 900 exhibits high oxygen reduction reaction (ORR) activities with an excellent half-wave potential and high methanol tolerance. • The optimal electrocatalyst can be used as air electrode materials in high-performance zinc-air batteries. • Density functional theory (DFT) calculations reveal that N, S-dual dopant can create extra active sites with higher catalytic activity than the isolated N -dopant. The construction of hollow mesoporous carbon nanospheres (HMCS) avoiding the use of traditional soft/hard templates is highly desired for nanoscience yet challenging. Herein, we report a simple and straightforward template-free strategy for preparing nitrogen, sulfur dual-doped HMCSs (N/S-HMCSs) as oxygen reduction reaction (ORR) electrocatalysts. The unique hollow spherical and mesoporous structure was in-situ formed via a thermally initiated hollowing pathway from an elaborately engineered covalent triazine framework. Regulation of pyrolysis temperatures contributed to precisely tailoring of the shell thickness of HMCSs. The resulting N/S-HMCS 900 (pyrolyzed at 900 °C) possessed high N and S contents, large specific surface areas, rich and uniform mesopores distribution. Consequently, as a metal-free ORR electrocatalyst, N/S-HMCS 900 exhibits a high half-wave potential, excellent methanol tolerance and great long-term durability. Additionally, density functional theory calculations demonstrate that N, S-dual dopant can create extra active sites with higher catalytic activity than the isolated N -dopant. This strategy provides new insights into the construction of hollow and mesoporous multi-heteroatom-doped carbon materials with tunable nanoarchitecture for various electrochemical applications. [ABSTRACT FROM AUTHOR]

Bifunctional catalyst was prepared by one-step pyrolysis of trimetallic ZIF. The obtained catalyst showed excellent charge–discharge stability in rechargeable Zn-air battery. • A facile and effect strategy is proposed for the synthesis of catalyst precursor. • This strategy reduces the adverse effects of the pyrolysis process on the catalyst. • The coexistence of Co NPs and CoFe-N x improves the ORR/OER activity. • The catalyst displays excellent durability as a cathode for Zn-air battery. Searching for high active, low cost and durable catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) remains challenge in developing metal-air battery cathodes. Herein, we proposed a novel bifunctional catalyst derived from the pyrolysis of Co/Fe/Zn trimetallic zeolitic imidazolite framework. The obtained Co@CoFe 0.01 N C catalyst displays desirable activity for both ORR and OER (E 1/2 = 0.844 V, E j=10 = 1.654 V). The Zn-air battery equipped with Co@CoFe 0.01 N C catalyst on the cathode exhibits a high peak power density of 174.1 mW cm−2, which is much superior than that of commercial 20% Pt/C (87.6 mW cm−2). Significantly, the designed Co@CoFe 0.01 N C presents an outstanding stability for over 100 h in rechargeable Zn-air battery. [ABSTRACT FROM AUTHOR]

Fe 3 C wrapped by N -doped hierarchically porous graphitic layers (NPGL) using g-C 3 N 4 and dopamine as dual-nitrogen-source exhibits superior ORR performances in alkaline medium. Rational design of low-cost and high-efficient non-precious-metal catalysts for oxygen reduction reaction (ORR) has drawn tremendous attention. Herein, we report a facile template-sacrificing strategy to synthesize N -doped hierarchically porous graphitic layers wrapped iron carbide (Fe 3 C@NPGL). Cost-effective graphitic carbon nitride (g-C 3 N 4) combined with dopamine were used as dual-nitrogen-source which provide more active sites for ORR. By virtue of abundant Fe-N coordination sites and unique porous structure of NPGL, the as-fabricated Fe 3 C@NPGL exhibits excellent ORR performances with a half-wave potential of 0.87 V, a limited current density of 6.3 mA cm−2, and a low peroxide yield (<2.5%), which outperform commercial Pt/C and most of the reported non-precious-metal catalysts. This work provides a feasible strategy to design novel ORR electrocatalysts. [ABSTRACT FROM AUTHOR]

• Auricularia is used to prepare Co 8 FeS 8 /NSC via thorough coordination of precursors. • MFC with Co 8 FeS 8 /NSC (900 °C) cathode has higher performance and stability than Pt/C. • Co2+ and Fe2+ in Co 8 FeS 8 provide more active sites to achieve rapid kinetics for ORR. • Co 8 FeS 8 with multiple atoms boosts side-on oxygen adsorption to enhance ORR activity. • Porous structure with N-species has abundant available channels for mass transfer. The main issues regarding the practical application of microbial fuel cells (MFCs) are the poor activity and tolerance of oxygen reduction reaction (ORR) catalysts in wastewater. In this study, Auricularia chelated with Co, Fe and S ions is used as a nitrogen (N)-enriched carbon source to prepare N-doped bimetallic sulfide (Co 8 FeS 8)-embedded carbon spheres (Co 8 FeS 8 /NSC) using a hydrothermal method. The effects of various temperatures (800–950 °C) on the structure and catalytic activity of Co 8 FeS 8 /NSC catalysts are investigated. The MFC with a Co 8 FeS 8 /NSC (900 °C) cathode obtained the maximum power density of 1.002 W m−2, which is higher than that of Pt/C (0.88 W m−2). After 1440 h of operation, the power density of the Co 8 FeS 8 /NSC (900 °C) cathode only declined by 5.49%, indicating that the Co 8 FeS 8 activity, charge transfer and O 2 transport were slightly influenced by the attached microbes and poisonous substances in the wastewater. The electrochemical results indicate that Co 8 FeS 8 /NSC (900 °C) mainly proceeds by a 4e− ORR pathway, indicating that Co 8 FeS 8 (Co2+ and Fe2+) wrapped in NSCs (carbon spheres) can trigger synergistic effects to provide more active sites and high electrical conductivity to achieve the rapid kinetics required for the ORR. Moreover, the porous structures of the NSCs (220.97 m2 g−1) with incorporated pyridinic N, pyrrolic N and graphitic N can provide abundant available channels for O 2 and OH− transport to ensure the preferential accessibility of the reactant molecules to active sites. This indicates that Auricularia-derived Co 8 FeS 8 /NSC catalysts have great potential as alternatives for precious metal-based catalysts in neutral electrolyte MFCs. [ABSTRACT FROM AUTHOR]

A facile, low-cost and solution-free synthesis was utilized to achieve Fe-N-C core-shell nanostructures, which exhibited excellent ORR performance in alkaline medium. Core-shell Fe 3 C@N C nanostructures constructed by Fe 3 C core encapsulated in N-doped carbon nanotubes (FFCN-MP4000) is designed and readily prepared via a facile and economical solid-state chemical route. By controlling the proportion of C and N in the starting materials, the composition of Fe N C core-shell nanotubes was optimized, then provided more possible active sites as electrocatalysts, exhibited superior oxygen reduction performance. Onset potential (E onset) of 0.96 V versus reversible hydrogen electrode (RHE) and half-wave potential (E 1/2) of 0.83 V vs RHE was obtained in 0.1 M KOH, which are comparable to those of the commercial Pt/C catalyst (E onset = 0.98 V, E 1/2 = 0.84 V vs RHE). Notably, the limited current density for FFCN-MP4000 can reach to 6.6 mA cm−2, and it efficiently catalyzes 4-electron reduction of oxygen (n = 3.98) with a hydrogen peroxide yield of below 2.2%. In addition, the methanol tolerance and durability are even superior to commercial Pt/C catalyst. This work provides a facile and economical strategy for the feasible design of oxygen reduction reaction (ORR) electrocatalyst with high activity and low cost in alternative commercial Pt/C electrocatalyst. [ABSTRACT FROM AUTHOR]

High-density Co 9 S 8 nanocrystals encapsulated within N, S dual-doped spherical nanostructure : A cobalt-gluconate complexes derived Co 9 S 8 /N, S co-doped micro/mesoporous carbon sphere is developed as a promising oxygen-reduction electrocatalyst. The exploration of an efficient nonprecious electrocatalyst for oxygen reduction reaction (ORR) is critical to the commercialization of various electrochemical energy-conversion devices. Herein, a cobalt-gluconate-derived nitrogen and sulfur dual-doped micro/mesoporous carbon sphere (Co 9 S 8 /N, S-MCS) with encapsulated high-density cobalt sulfide (Co 9 S 8) nanocrystals is developed by annealing and subsequent high-temperature vulcanization. Particularly, the vulcanization temperature has a critical impact on the formation of high-density Co 9 S 8 nanocrystals. Benefiting from the favorable material characteristics of large surface area, abundant micro/mesopores and high graphitic nanostructures, as well as the synergistic effects between high-density Co 9 S 8 nanocrystals and N, S-dual doped graphitic carbon shells, the resulting catalyst demonstrates superior ORR catalytic activity and durability compared to platinum/carbon (Pt/C) catalyst. More notably, the proposed approach can be extended potentially to fabricate other transition metal sulfide (or oxide, carbide) based electrocatalysts. [ABSTRACT FROM AUTHOR]

The development of cost-effective and highly-efficient electro-catalysts is essential for the advancement of proton exchange membrane fuel cells (PEMFC). We present a novel nitrogen-sulphur co-doped carbon nanotubes-few layer graphene1D-2D hybrid support formed by partially exfoliating multiwall carbon nanotubes (PECNT), to improve interface bonding to catalyst nanoparticles. Detailed Raman spectroscopy and STEM-EDS analyses demonstrate that active sites on the co-doped hybrid support ensure both uniform distribution and improved bonding of the catalyst nanoparticles to the support. Electrochemical studies show that Pt nanoparticles decorated on nitrogen-sulphur co-doped PECNT (Pt/NS-PECNT) have higher electrochemical active surface area and mass activity accompanied by low H 2 O 2 formation and improved positive half-wave potential, as compared to those decorated on co-doped rGO-incorporated PECNT hybrid structure (Pt/NS-(rGO-PECNT)). Fuel cell measurements demonstrate a higher power density for our novel (Pt/NS-PECNT) electro-catalyst when compared to both Pt/NS-(rGO + PECNT), and commercial Pt/C electro-catalyst. We demonstrate in this work that the interconnectivity between Pt-nanoparticles and the dopant or defect sites on the support play a crucial role in enhancing the ORR activity, fuel cell performance, and durability of the catalyst. [ABSTRACT FROM AUTHOR]

Transition metal and nitrogen (N) doped carbon materials are regarded as promising alternatives to expensive Pt-based catalysts for oxygen reduction reaction (ORR), thanks to their natural abundance, good stability and high energy conversion efficiency. Herein, a facile efficient pyrolysis approach was developed to prepare graphene-encapsulated Co nanoparticles (NPs) embedded in porous nitrogen-doped graphitic carbon nanosheets (Co@G/N-GCNs), in which g-C 3 N 4 served as C and N sources, and cobalt phthalocyanine (CoPc) as the Co- and N-sources. The as-obtained catalyst exhibited exceptional ORR activity (E 1/2 = 0.86 V vs. RHE), good durability (12 mV negative shift of E 1/2 after 2000 cycles), and strong methanol resistance, surpassing those of commercial Pt/C catalyst in alkaline conditions. The pyrolysis temperature and entrapped contents of metal NPs had critical impacts on the ORR features. This work offers a feasible strategy for designing low-cost non-noble-metal catalysts for energy storage and conversion. [ABSTRACT FROM AUTHOR]

• Ultrafine FeCo nanoparticles anchored on N-doped porous carbon (FeCo-NC). • FeCo-NC with high specific surface areas and pore volume. • FeCo-NC with superior oxygen reduction reaction (ORR) activity. • FeCo-NC with better stability than Pt. • FeCo-NC with Pt-like Zn-air battery performance. Oxygen reduction reaction (ORR) is a key process in renewable energy conversion and storage technologies, including fuel cells and metal-air batteries. Pt is a highly efficient ORR electrocatalyst, but its large-scale application is severely prohibited by the high cost. In the pursuit of cost-effective electrocatalysts, it is urgent to develop non-noble metal ORR catalysts. Herein, we report a facile strategy for synthesizing an ORR electrocatalyst based on ultrafine bimetallic FeCo nanoparticles (NPs) anchoring on N-doped porous carbon matrix (FeCo-NC). By optimizing the ratio of Fe and Co, the FeCo-NC-1 catalyst exhibits excellent performance for ORR with the half-wave potential of 0.84 V and limiting current density of −5.3 mA cm−2, which is comparable to the commercial Pt/C catalyst. When applied to Zn-air batteries, FeCo-NC-1 catalyst possesses a high open-circuit potential (1.50 V) and large specific capacity (726.2 mA h g−1) with a good long-term stability and methanol-tolerant capability, which are even superior to the commercial Pt/C catalyst. The first-principle calculations indicate the bimetallic FeCo-NC has stronger O 2 adsorption than the single metal nitrogen-doped carbon catalysts (Fe-NC and Co-NC), which is the primary reason for the better ORR performance. We believe this work can be helpful for the development of inexpensive and high-efficient ORR electrocatalysts. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract The design of low-cost, highly efficient, and the durable catalyst is essential to replace commercial platinum metal-based catalysts for the oxygen reduction reaction (ORR) in fuel cell applications. Herein, a novel mesoporous hybrid based on nitrogen-doped graphene nanosheets-stabilized layered spinel zinc manganese oxide (Zn 2 Mn 3 O 8 -NG) is successfully engineered and applied as an effective catalyst to accelerate the ORR process in alkaline medium. Electrochemical performance analysis of this catalyst shows excellent catalytic activity with high current density, positive onset potential (−0.013 V), and positive half-wave potential (−0.12 V), which are relative to the commercial Pt/C in 0.1 M KOH electrolyte. The kinetic study of the synthesized catalyst towards ORR demonstrates a direct 4e− transfer pathway. The methanol tolerance and long-term stability test suggest its superior behavior to Pt/C. The excellent performance of the Zn 2 Mn 3 O 8 -NG is attributed to the synergistic effects of nanosized Zn 2 Mn 3 O 8 nanocrystals and NG nanosheets, which effectively improve the electroactive surface area, conductivity, diffusion channels, and mass transfer ability. This result suggests that the resulting catalyst could be used as a potential alternative of Pt-based catalysts towards ORR application. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract In this study, we successfully demonstrate an efficient, metal-free nitrogen, fluoride-codoped carbon (NFC) oxygen reduction reaction (ORR) electrocatalyst, which is produced by directly pyrolyzing melamine hydrogen fluoride salt (using as a single N and F precursor for the first time) mixed with carbon black BP2000 in a N 2 atmosphere. The ORR electrocatalytic performances are evaluated by rotating ring disk electrode experiments in 0.1 M KOH. The NFC electrocatalyst prepared at the optimized temperature of 1000 °C (NFC1000) demonstrates a high ORR electrocatalytic activity with a peak potential of 0.82 V (vs. RHE), half-wave potential of 0.82 V (vs. RHE), predominant direct 4-electron reaction pathway, and good durability and methanol tolerance. Transmission electron microscopy equipped with mapping, X-ray diffraction and X-ray photoelectron spectroscopy results indicate that NFC1000 possesses an amorphous carbon structure with a homogenous codoped distribution of N and F at 2.25 at% and 1.52 at%, respectively. N 2 adsorption-desorption analysis reveals that the as-prepared NFC1000 has a high surface area of 1169 m2 g−1. This study provides a feasible approach to synthesize low-cost and highly efficient metal-free heteroatom-doped carbon-based electrocatalysts. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Nonprecious-metal electrocatalysts have been intensively investigated, but how to keep a balance between their sustainability and competitive performance for the oxygen reduction reaction (ORR) is still a big challenge for energy applications. In this work, a type of bimetal- and nitrogen-codoped mesoporous carbon electrocatalyst (FeCo-N/C-800) was successfully synthesized via a simple hydrothermal method, followed by a calcination process at 800 °C in nitrogen atmosphere and an acid-etching process. The obtained FeCo-N/C-800 can act as a high-performance ORR catalyst with high onset and half-wave potentials (0.94 and 0.85 V), a large limiting current density (5.94 mA cm−2) and a four-electron reaction process in 0.1 M KOH solution, which can be comparable with commercial Pt/C catalyst. Additionally, the FeCo-N/C-800 exhibited superior long-term durability and high methanol tolerance. The excellent electrocatalytic performance of the FeCo-N/C-800 can be ascribed to the mesoporous structure (bimodal pores system), the synergetic interaction of the multiple ORR active sites, suitable N-doping level and the highly conductive carbon matrix. These structural features can promote efficiently the mass and electron transfer, provide abundant active sites for the adsorption and reaction of oxygen molecules, and thus improve the reaction kinetics. The present study not only provides a strategy for the synthesis of carbon-based electrocatalyst with high ORR catalytic activity and stability, but also demonstrates that the bimetal- and nitrogen-codoped carbon materials could be a class of competitive candidate for non-noble metal-based electrocatalysts. [ABSTRACT FROM AUTHOR]

Graphical abstract The B N bond contents calculated from either N or B XPS spectra are less than 8.2% of total N or B atoms for 3D porous Fe 3 C@B 1.0 NPCFs-900 networks as the electrostatic repulsion effect between precursors. Abstract In this paper, polyvinylpyrrolidone (PVP) and 4-hydroxybenzeneboronic acid (o-HPBA) are polarized in alkaline solution and then employed as boron (B) and nitrogen (N) sources. Fe(AC) 2 /o-HPBA/PVP/DMF(N,N-Dimethylformamide) slurries are first electrospunned into three-dimensional (3D) networks. Due to the electrostatic repulsion between negatively charged O− groups surrounding N and B atoms, N and B atoms can be kept far away from each other. Upon optimizing o-HPBA dosages, the maximum amount of isolated B and N atoms are successfully doped into the 3D porous iron carbide (Fe 3 C) embedded B and N co-doped carbon fibers (Fe 3 C@B 1.0 NPCFs) networks with tiny B N clusters. Electrochemical measure results demonstrate that Fe 3 C@B 1.0 NPCFs exhibit much better oxygen reduction reaction (ORR) activity than 20 wt% Pt/C in alkaline electrolyte. In acidic electrolyte, Fe 3 C@B 1.0 NPCFs also displays ORR activity comparable to Pt/C (its onset and half-wave potentials are just 40 and 50 mV more negative than those of Pt/C). Moreover, Fe 3 C@B 1.0 NPCFs show better stability and methanol tolerance ability than Pt/C for ORR in both alkaline and acidic solutions. This work opens new avenues for intentionally preventing the malignant combination of B and N atoms and boosting the electrocatalytic activity of B and N co-doped and Fe 3 C embedded carbon catalysts. [ABSTRACT FROM AUTHOR]

An iron and nitrogen co-doped 3D porous carbon catalyst with high performance for oxygen reduction reaction (ORR) is produced by pyrolysis. The precursor is a mixture of red date, ferrous (Ⅱ) acetate, and graphitic carbon nitride (g-C 3 N 4 ). g-C 3 N 4 is the nitrogen source and also the sacrificial template, which plays a key role in the formation of a porous nitrogen rich carbon structure with high surface area. It is found that active sites and catalytic performance of synthetic materials are significantly influenced by the Fe content. In comparison with commercial Pt/C catalyst, the synthetic Fe-N-C with optimized composition exhibits comparable ORR activity and superior methanol tolerance. This work provides a feasible approach to develop cost-effective and highly efficient non-precious metal electrochemical catalysts for oxygen reduction. [ABSTRACT FROM AUTHOR]

Doping-type carbon matrixes not only play a vital role on their electrochemical properties, but also are capable of suppressing the crush and aggregation phenomenon in the electrode reaction process for pristine metallic compound. Herein, graphite coated cobalt and cobalt sulfide nanoparticles decorating on sulphur and nitrogen dual-doped mesoporous carbon (Co@Co 9 S 8 /S- N -C) was fabricated by a combined hydrothermal reaction with pyrolysis method. Benefited from g-C 3 N 4 template and original synthetic route, as-obtained Co@Co 9 S 8 /S- N -C possessed high specific surface area (751.7 m 2 g −1 ), large pore volume (1.304 cm 3 g −1 ), S and N dual-doped component and relative integrated graphite skeleton, as results it was developed as decent oxygen reduction electro-catalyst and ultra-long-life Li-ion battery anode. Surprisingly, compared with commercial Pt/C, it displayed a higher half-wave potential (0.015 V positive) and lower Tafel slop (66 mV s −1 ), indicating its superior ORR activities. Moreover, the ultra-long-life cyclic performances were revealed for lithium ion battery, exhibiting the retention capacities of 652.1 mAh g −1 after 610 cycles at 0.2 A g −1 , 432.1 and 405.7 mAh g −1 at 5 and 10 A g −1 after 1000 cycles, respectively. We propose that the synergistic effect of structure and chemical component superiorities should be responsible for the remarkable electrochemical behaviors of the Co@Co 9 S 8 /S- N -C. [ABSTRACT FROM AUTHOR]

Nitrogen-doped graphene quantum dots (N-GQDs) exhibit exciting properties in the oxygen reduction reaction (ORR) for ample electrocatalytic edging and N-doped active sites. However, low yield and high dispersity of N-GQDs prohibit their direct application as the electrocatalyst. In this paper, two facile hydrothermal progress were developed to synthesize the high-yield N-GQDs with the diameter of ca. 2–6 nm and the hybrid of N-GQDs/Reduced Graphene Oxide (N-GQDs/r-GO). The results demonstrated that the N-GQDs/r-GO display remarkable electrocatalytic activity. Moreover, it can be found that the pyridinic-N plays a major role in ORR. Both the average electron transfer number and the onset potential depend on the content of pyridinic-N. The proposed synthesis strategy is facile and low-cost, serving as a feasible method for the development of highly efficient electrocatalysts. [ABSTRACT FROM AUTHOR]

Nitrogen doped carbon nanofiber films (NCNFs) is successfully synthesized via the carbonization of polypyrrole (PPY) functionalized electrospun polyacrylonitrile (PAN) nanofibers. Benefitting from the nitrogen-doped one-dimensional (1D) nanostructure, the as-obtained NCNFs show multifunctional applications as electrode materials for lithium ion batteries (LIBs) and catalysts for oxygen reduction reaction (ORR). For LIB application, the obtained NCNFs could be directly used as flexible, free-standing and binder-free electrode, which exhibits high specific capacity up to 698.9 mAh g −1 (higher than that of carbon nanofiber derived from PAN), long life over 160 cycles, and good rate capability (148.8 mAh g −1 at 2 A g −1 ). In addition, a preliminary ORR catalytic activity study has demonstrated that the NCNFs exhibit good catalytic activity. Therefore, these properties endorse NCNFs as auspicious candidates for both LIBs and ORR. [ABSTRACT FROM AUTHOR]