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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]

The development of precious metal-free (M-N-C) catalysts for the oxygen reduction reaction (ORR) is considered crucial for reducing fuel cell costs. Herein, Co-Zn/NC interconnected frameworks with uniformly dispersed Co nanoparticles and graphitic carbon are designed and successfully synthesized through the in situ growth of zeolitic imidazolate frameworks (ZIF67 and ZIF8) along with biomass nano-microfibrillar cellulose (MFC), followed by pyrolysis. A Co-Zn/NC composite is prepared by combining Co-Zn/NC with a perfluorosulfonic acid polymer. The Co-Zn/NC composite catalyst exhibits excellent ORR catalytic activity (E0 = 0.974 V vs. RHE, E1/2 = 0.858 V vs. RHE) and good long-term durability, with 90% current retention after 10000s, surpassing that of commercial Pt/C in alkaline media. The hierarchical porous structure, coupled with the uniform distribution of Co nanoparticles and nitrogen doping, contributes to superior electrocatalytic performance, while the interconnected frameworks and graphitic carbon ensure good stability. Additionally, the Co-Zn/NC composite demonstrates promising applications in acidic media. This strategy offers significant guidance to develop advanced non-precious metal carbon-based catalysts for highly efficient and stable ORR. [ABSTRACT FROM AUTHOR]

As the world faces an escalating energy crisis, the necessity of adopting alternative energy sources becomes increasingly evident. Despite challenges, the imperative to prioritise these eco‐friendly alternatives remains paramount in paving the way for a more sustainable and resilient future for our planet and its inhabitants. The pursuit of sustainable energy sources has brought the oxygen reduction reaction (ORR) into the spotlight as a crucial cathodic reaction in energy‐converting systems, notably fuel cells (FCs). These FCs hold tremendous promise in providing an eco‐friendly and efficient energy supply. However, the widespread implementation of FCs is hindered by their reliance on expensive and scarce noble metal catalysts, such as platinum (Pt), which pose economic and environmental challenges. Hence, this work reports the preparation, characterisation (FTIR, XPS, SEM and EDX) and application of four composites based on doped‐carbon materials (CM) and on the Wells‐Dawson POM salt K6⋅α‐[P2W12Mo6O62] ⋅ 19H2O (P2W12Mo6@MWCNT_N8, P2W12Mo6@MWCNT_N6, P2W12Mo6@MWCNT_S6, and P2W12Mo6@GF_S6) as ORR electrocatalysts in alkaline medium (pH=13). The successful doping of the carbon materials with nitrogen (N) and sulphur (S) and the incorporation of the polyoxometalate were verified through comprehensive structural characterisation. Overall, P2W12Mo6@MWCNT_N8 exhibited favourable onset potentials of 0.84 V vs. RHE, highlighting its high catalytic activity. Additionally, the catalyst showed excellent tolerance to methanol crossover, retaining 91 % of initial current, which is crucial for practical fuel cell applications. Furthermore, the P2W12Mo6@MWCNT_N8 catalyst showed commendable stability, retaining 81 % of its initial current after 36000 seconds at an operating potential of E=0.46 V vs. RHE. These encouraging results denote the significant potential of this electrocatalyst in advancing sustainable energy conversion technologies. [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]

The search of active, stable and low costs catalysts for the oxygen reduction reaction (ORR) is crucial for the extensive use of fuel cells and metal–air batteries. The development of metal-free catalysts, instead of platinum-based materials, can dramatically reduce the cost and increase the efficiency of these devices. In this work, carbon nanohorns (CNHs) have been covalently functionalized with N-containing heterocycles by the Tour reaction protocol and tested as metal-free ORR catalysts. The insertion of N-functionalities favored the complete reduction of oxygen to hydroxyl ions, while their absence favored the production of hydrogen peroxide. With the aim of determining the N-species responsible for the ORR activity of CNHs, photoemission and electrochemical measurements were combined. Results suggest that protonated N is the main species involved in the ORR process, facilitating the adsorption of oxygen, with their consequent reduction to neutral hydrogenated N species. [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]

An efficient and low-cost oxygen catalyst for the oxygen reduction reaction (ORR) was developed by in situ growth of Mn-Mo oxide nanoparticles on nitrogen-doped carbon nanotubes (NCNTs). Doped nitrogen effectively increases the electron conductivity of the MnMoO4@NCNT complex and the binding energy between the Mn-Mo oxide nanoparticles and carbon nanotubes (CNTs), leading to fast charge transfer and more catalytically active sites. Combining Mn and Mo with NCNTs improves the catalytic activity and promotes both electron and mass transfers, greatly enhancing the catalytic ability for ORR. As a result, MnMoO4@NCNT exhibited a comparable half-wave potential to commercial Pt/C and superior durability, demonstrating great potential for application in renewable energy conversion systems. [ABSTRACT FROM AUTHOR]

Metal‐free carbon‐based catalysts have attracted significant attention owing to their unique electronic structure and excellent catalytic activity for the oxygen reduction reaction (ORR). Recently, several heteroatom‐doped carbon catalysts with ORR performances comparable with those of state‐of‐the‐art Pt‐based catalysts have been reported. However, the intrinsic influence of heteroatoms on the catalytic activity has not been thoroughly investigated to date. This paper reports porous carbons co‐doped with N and S, prepared using an ion‐exchange resin and tetramethylammonium cations, with an onset potential of 0.93 V versus reversible hydrogen electrode (RHE) and a half‐wave potential of 0.79 V versus RHE. First‐principles calculations reveal that the change in the atomic charge caused by the co‐doping of N and S is important for inducing a high ORR activity. This paper presents a rational synthetic strategy for metal‐free catalysts and provides fundamental insights into their electrocatalysis. [ABSTRACT FROM AUTHOR]

Metal/nitrogen-doped carbon single-atom catalysts (M−N−C SACs) show excellent catalytic performance with a maximum atom utilization and customizable tunable electronic structure. However, precisely modulating the M−Nx coordination in M−N−C SACs remains a grand challenge. Here, we used a N-rich nucleobase coordination self-assembly strategy to precisely regulate the dispersion of metal atoms by controlling the metal ratio. Meanwhile, the elimination of Zn during pyrolysis produced porous carbon microspheres with a specific surface area of up to 1151 m2 g−1, allowing maximum exposure of Co−N4 sites and facilitating charge transport in the oxygen reduction reaction (ORR) process. Thereby, the monodispersed cobalt sites (Co−N4) in N-rich (18.49 at%) porous carbon microspheres (CoSA/N−PCMS) displayed excellent ORR activity under alkaline conditions. Simultaneously, the Zn−air battery (ZAB) assembled with CoSA/N−PCMS outperformed Pt/C+RuO2-based ZABs in terms of power density and capacity, proving that they have good prospects for practical application. [ABSTRACT FROM AUTHOR]

Nitrogen-doped graphene is currently recognized as one of the most promising catalysts for the oxygen reduction reaction (ORR). It has been demonstrated to act as a metal-free electrode with good electrocatalytic activity and long-term operation stability, excellent for the ORR in proton exchange membrane fuel cells (PEMFCs). As a consequence, intensive research has been dedicated to the investigation of this catalyst through varying the methodologies for the synthesis, characterization, and technologies improvement. A simple, scalable, single-step synthesis method for nitrogen-doped graphene oxide preparation was adopted in this paper. The physical and chemical properties of various materials obtained from different precursors have been evaluated and compared, leading to the conclusion that ammonia allows for a higher resulting nitrogen concentration, due to its high vapor pressure, which facilitates the functionalization reaction of graphene oxide. Electrochemical measurements indicated that the presence of nitrogen-doped oxide can effectively enhance the electrocatalytic activity and stability for ORR, making it a viable candidate for practical application as a PEMFC cathode electrode. [ABSTRACT FROM AUTHOR]

Graphene supported FeN5 active sites, exhibiting high activity and stability of oxygen reduction reaction, enable a H2-air fuel cell to decay little during the latter 20–100 h operation. [Display omitted] • Electrochemically-exfoliated graphene improves forming FeN 5 with NH 3. • Graphene benefits catalytic stability of oxygen reduction reaction. • Fuel cell keep stable with little decay in latter 80 h operation. • High half-wave potentials in alkaline medium (0.940 V). Metal-nitrogen-carbon catalytic material, generally thought as a promising low-cost electrocatalyst of oxygen reduction reaction (ORR), surfers from long-term catalytic durability for fuel cell and metal-air battery. Here, we describe an approach of synthesizing electrochemically exfoliated graphene supported penta-nitrogen coordinated iron exhibiting encouraging ORR catalytic activity and durability. The synthesized catalyst exhibits high half-wave potentials in alkaline medium (E 1/2 0.940 V) enabling high-performance zinc-air battery and in acidic condition for durable fuel cell with a high peak power density (630 mW cm−2). The current density of a proton exchange membrane fuel cell loading the catalyst as cathode tends to decay little after initial hours under H 2 -air measurement, remarkably inhibiting commonly decline tendency of iron–nitrogen-carbon catalysts. DFT calculation combined with extensive experimental investigations demonstrate that penta-nitrogen coordinated iron supported by graphene is thermodynamically stable, and thus benefits the catalytic stability of ORR. [ABSTRACT FROM AUTHOR]

The exploration of non-Pt catalysts with high electrocatalytic activity and durability is especially important for cathodic oxygen reduction reaction (ORR) in fuel cell. Here, cobalt and nitrogen doped hollow carbon sphere-bamboo like carbon nanotube (Co/NHCS-BCNT) is prepared by using SiO 2 sphere as sacrificial template. Co nanoparticles are confined in the cavity and top end of the in-situ formed BCNT, which can not only avoid the agglomeration of Co nanoparticles but also inhibit corrosion in caustic electrolyte. The synergistic effect between NHCS and well-dispersed Co particles makes Co/NHCS-BCNT have superior catalytic activity toward ORR. The electrochemical surface area (ECSA) of Co/NHCS-BCNT is 222 cm2, which is higher than those of NHCS (164 cm2) and HCS (135 cm2). The onset potential and half-wave potential of Co/NHCS-BCNT are 0.941 V and 0.814 V, respectively, which are close to commercial Pt/C (0.949 V, 0.807 V). The Tafel slope of Co/NHCS-BCNT (63.8 mV dec-1) is lower than that of Pt/C (71.7 mV dec-1). In addition, Co/NHCS-BCNT shows excellent durability and fuel selectivity. [Display omitted] [ABSTRACT FROM AUTHOR]

Atomically distributed iron electrocatalyst is valid for oxygen reduction reaction (ORR). However, accurate regulation of the structure improving its intrinsic activity is a challenge. Herein, a dual-atom catalyst FeCu-NC with atomically distributed Fe and Cu co-anchored on porous N-doped carbon is obtained. The FeN 4 and CuN 3 couple sites bridged by two nitrogen atoms, exist as Fe(II,III)N 2 (µ 2 -N) 2 Cu(I,II)N moieties with the metal distance of ∼2.5 Å in the structure of FeCu-NC. The synergistic effect of Fe and Cu dual-atom reducing the dissociation energy of *OOH intermediate, allows an optimized 4e- ORR reaction pathway. The FeCu-NC exhibits high-efficiency ORR activity with the half-wave potential (E 1/2) of 0.889 V (vs RHE) and outstanding stability without obvious decay for the E 1/2 after 10,000 cycles. The FeCu-NC based Zn-air battery presents large specific capacity of 795 mAh g−1 and energy density of 998 Wh kg−1 as well as high charge-discharge cycling stability superior to the Pt/C. [Display omitted] • A dual-atom catalyst FeCu-NC with Fe(II,III)N 2 (µ 2 -N) 2 Cu(I,II)N moieties is prepared. • The synergistic effect of Fe and Cu clearly reduces the dissociation energy of *OOH. • The FeCu-NC has a high ORR activity in an optimized 4e- reaction pathway. • The FeCu-NC based Zn-air battery exhibits a large stable energy density. [ABSTRACT FROM AUTHOR]

Single atom catalysts (SACs) are constituted by isolated active metal centers, which are heterogenized on inert supports such as graphene, porous carbon, and amorphous carbon. The thermal stability, electronic properties, and catalytic activities of the metal center can be controlled via manipulating the neighboring heteroatoms such as nitrogen, oxygen, and sulfur. Due to the atomical dispersion of the active catalytic centers, the amount of metal required for catalysis can be decreased. Furthermore, new possibilities are offered to easily control the selectivity of a given transformation process as well as to improve turnover frequencies and turnover numbers of target reactions. Among them, Fe--N--C single atom catalysts own special electronic structure, and have been widely used in many fields of electrocatalysis. This review aims to summarize the synthesis of Fe--N--C based on anchoring individual iron atoms on carbon/graphene. The spin-related properties of Fe--N--C catalysts are described, including the relation between spin and electron structure of Fe--Nx as well as the coupling between electronic structure of Fe--Nx and electronic (orbit) of CO2, N2 and O2. Next, mechanistic investigations conducted to understand the specific behavior of Fe--N--C catalysts are highlighted, including C, N, O electro-reduction. Finally, some issues related to the future developments of Fe--N--C are put forward and corresponding feasible solutions are offered. [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]

The development of efficient and inexpensive cathode catalysts contributes to energy conservation. Herein, nitrogen-doped carbon nanofiber (CNF) composites (Cu@N-CNFs) loaded with copper nanoparticles were successfully synthesized as cathode electrocatalysts for microbial fuel cells (MFCs), utilizing metal-organic frameworks (MOFs) and bacterial cellulose (BC) as precursors. The characterization results show that Cu@N-CNFs has a large specific surface area and contains catalytic active substances such as pyridine nitrogen and graphite nitrogen, along with that the graphitization degree of carbon skeleton structure is high. Therefore, Cu@N-CNFs has outstanding catalytic performance in alkaline and neutral environments, with half-wave potentials of 0.83 V and 0.78 V, as well as limiting current densities of −5.70 mA cm−2 and −5.73 mA cm−2, respectively. Moreover, these performances are comparable to those of Pt/C. The composite material is coated on the surface of the carbon cloth and processed into MFC cathode, which has a good improvement in its power production performance. • Cu@N-CNFs has excellent catalytic performance in alkaline and neutral environments. • Catalyst was further constructed as microbial fuel cells. • Cu@N-CNFs has a large specific surface area and contains catalytic active substances [ABSTRACT FROM AUTHOR]

Single atomic catalysts (SACs), especially the catalysts featured by well-developed M-N 4 moieties, show excellent catalytic activity and spark enormous attention. However, the highly symmetric active sites may result in some degenerate electronic states for the d orbitals of the center metal atom, which suffer from the unsatisfactory adsorption-desorption behaviors during reaction. Herein, we develop an asymmetric anchor site by two types of nitrogen (sp-N and pyridinic N) created in the inherent edge-rich carbon domain of hydrogen-substituted graphdiyne (HsGDY), where atomic catalyst like manganese atoms can be asymmetrically anchored on the one side of hexagon carbon rings. The abundant elegant hexagon carbon rings on HsGDY not only facilitate the creation of edge sites, but also provide available space for the coordination of terminal ligands (OH) with Mn atoms. The as-synthesized Mn-N-HsGDY exhibits excellent ORR activity and an impressive long-term cyclability for over 3800 cycles in a rechargeable Zn-air battery. [Display omitted] • A facile method for preparing asymmetric active sites is proposed. • The Mn atoms are anchored by sp-N and pyridinic N of HsGDY sideways. • The Mn SAC exhibits excellent ORR activity and can run over 3800 cycles in a zinc-air battery. [ABSTRACT FROM AUTHOR]

The carbon-based catalysts exhibit excellent electrocatalytic and stable performance toward oxygen reduction reaction (ORR), which are expected to replace expensive and scarce Pt-based catalysts. However, how to regulate the interaction between silver and carrier carbon dots (CD) to improve electrocatalytic performance toward oxygen reduction reaction (ORR) and stability, has not been systematically studied. In this study, we in-situ synthesized fluorine and nitrogen co-doped CD anchoring Ag nanoparticles by UV irradiation reduction method. The peak potential, onset-potential and half-wave potential of F, N-CD@Ag-0.1 are 0.85 V, 1.056 V, and 0.9 V, respectively, indicating outstanding ORR performance. The current density of F, N-CD@Ag-0.1 remains 97.5 % after 50, 000 s, showing more excellent stability than Pt/C. The impressive ORR catalytic activity and stability of F, N-CD@Ag-0.1 could be attributed to the strong anchoring effect of nitrogen-doped CD on Ag. This effect leads to a significant interaction and charge transfer between Ag and CD, thereby enhancing the charge transfer process during the catalytic reaction. This project aims to design a carbon dot/silver composite catalyst with high ORR catalytic performance and favorable stability. The implementation of this project provides good theoretical guidance for the design of carbon nanomaterial-based catalytic systems. • In-situ synthesized F, N-CD@Ag catalysts by UV irradiation reduction method. • The interaction between Ag and CD enhanced ORR catalytic activity and stability. • The catalyst exhibits onset potential and half-wave potential of 1.056 V & 0.90 V. [ABSTRACT FROM AUTHOR]

Numerous active sites and hierarchical pore structures are important for improving catalytic performance for the oxygen reduction reaction (ORR). In this work, a series of iron-nitrogen-doped porous carbon materials (Fe– N –C) with ORR catalytic activity were prepared by a one-step pyrolysis method using enzymolytic lignin as the raw material, soy protein isolate and iron chloride as dopants. The results showed that the samples with the best performance have abundant Fe-Nx active sites and mesoporous structures. At the same time, the electrocatalytic results indicate that the half-wave potential of catalyst was 0.84 V, which reached 96.55% of commercial Pt/C catalysts (E 1/2 = 0.86 V), it still preserves an initial current density of 92%, after 10,000 s of circulation, which is much better than Pt/C (86%). Due to the low cost, high activity and stable ORR property, the prepared non-precious metal electrocatalyst will play an important role in the applications of fuel cells. • Porous carbons prepared by a one-step pyrolysis method using enzymolytic lignin. • Successful doping of iron and nitrogen into the framework of mesoporous carbons. • Superior oxygen reduction activity for Fe–N codoped porous carbon. [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]

In addition to C, H and O, some biomass is also rich in mineral elements. The recovery and utilization of special mineral elements is of great significance to prepare functional materials and alleviate the current energy shortage. Herein, we describe a facile strategy for making full use of the chemical composition (C, Fe) and special structure of red blood cells (RBCs) from waste pig blood to fabricate a dual metal (Fe, Co)-nitrogen (N)-doped porous carbon catalyst by pyrolysis of a mixture of RBCs biomass, cobaltous acetate, and melamine. The porous catalyst displays a comparable activity for oxygen reduction reaction (ORR) to that of commercial Pt/C catalyst, with a half-wave potential of 0.821 VvsRHE in alkaline media and 0.672 VvsRHE in acid electrolyte. Especially, the as-prepared catalyst shows excellent methanol tolerance and stability in both acidic and alkaline electrolytes, which is superior to commercial Pt/C catalysts. The excellent ORR activity of FeCo-N/C(RBC) can be ascribed to the porous morphology and the cooperation between metal and nitrogen species. This work provides a novel idea of exploiting the composition of renewable biomass to modulate the activity and stability of carbon-based ORR 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]

The development of active and durable proton exchange membrane fuel cell catalysts with high loading (ca. 40%) is critical for the commercialization of hydrogen fuel cells. Herein we report on the synthesis of a novel Pt/C catalyst using a novel bowl-like broken hollow carbon sphere (and N-doped sphere) support (carbon shell thickness ~ 4.6 nm). Highly dispersed Pt nanoparticles (dPt ~ 4 nm) were deposited on both supports and within the carbon shell. The Pt particles in the pores were exposed on both sides of the shell, while the shell porosity ensured pore confinement of the Pt. Both catalysts exhibited high electrochemical surface areas (60–65 m2 g−1) and cycling durability (6000 cycles) that was superior to a commercial benchmark Pt/C catalyst. These studies indicate that high loadings of confined small Pt particles on both sides of thin interconnected carbons can lead to high oxygen reduction reaction activities and durability. [ABSTRACT FROM AUTHOR]

The metal-nitrogen-carbon (M-N-C) type oxygen reduction reaction (ORR) catalysts are promising for hydroxide exchange membrane fuel cells, but catalysts with further improved performance are challenging. Here, we report the efficient improvement of the ORR activity of M-N-C catalysts by employing highly polarizable metal cation Ag+. Ag, Fe single atomic sites embedded in concave nitrogen doped carbon (Ag 1 Fe 1 /CNC) is successfully synthesized and shows high performance towards ORR, indicating by both the ultra-high half-wave potential of 0.917 V and membrane electrolyte assembly performance of peak power density up to 1.26 W cm−2. The binding energy of the ORR intermediates on the highly polarizable Ag site in Ag 1 Fe 1 /CNC was significantly tuned by the adjacent Fe site by more than 0.2 eV, and thus leading to a low theoretical ORR overpotential of only 0.398 V. The employment of the highly polarizable metal cation brings a novel and efficient approach to construct highly active catalysts. [Display omitted] • High performance oxygen reduction reaction catalyst Ag 1 Fe 1 /CNC is synthesized. • The highly polarizable Ag site shows ultra-high catalytic activity. • The Ag sites are significantly affect by the adjacent metals. • High membrane electrolyte assembly performance is achieved by using Ag 1 Fe 1 /CNC. [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]

• DFT calculations are used to investigate the ORR on Co-N/C catalysts. • Double sites with Co in the same carbon sheet and adjacent sheets are studied. • Dissociation of O 2 to 2O has large free energy barriers (>1 eV) on Co double sites. • The occurrence of Co double sites facilitates OOH dissociation to O and OH. • Co double sites can increase ORR activity and suppress H 2 O 2 formation. • We analyze the sensitivity of results to the chosen solvent model. Metal and nitrogen co-doped carbons (M-N/Cs) are promising alternatives to platinum-based catalysts for the oxygen reduction reaction (ORR). Here, density functional theory calculations are used to compare the ORR activity of Co single and double sites embedded in N-doped carbon. Two different models of a Co double site are investigated, one in which two single sites are stacked on top of each other and one which has two Co atoms next to each other in a single graphene sheet. For both it is found that the ORR can proceed via a dissociative mechanism that splits the ∗OOH intermediate into ∗O and ∗OH, but only for the double site in the graphene sheet does it result in a significant deviation from the scaling relations. The adsorption energies of the ORR intermediates are investigated using different implicit and explicit solvent models, showing some variation in the results. In particular, the addition of explicit water on the same side of the catalyst as the ORR intermediate can result in stabilisation due to hydrogen bonding, while an explicit water molecule adsorbed on the opposite side of the Co atom can have an effect due to the change in coordination which affects the splitting of the Co d orbitals. [ABSTRACT FROM AUTHOR]

• N and S doped carbon nanospheres were synthesized using heterocyclic compounds. • N atoms in precursors determines active sites of N and S dopants for ORR. • The site with Graphitic-N and Thiophenic-S dopants is the most active for ORR. • The work give an insight for designing ORR catalysts via selection of precursors. Elucidating the correlation of the polymer precursors and active sites formation of multi-heteroatom doped based carbon for oxygen reduction reaction (ORR) is essential to develop molecular-level design of highly efficient metal-free carbon catalysts. To achieve this goal, herein, two series of N doped and N, S co-doped carbon nanospheres were synthesized via pyrolysis of self-polymerized compounds of three analogous precursors of 2,6-Diaminopyridine, 4, 6-Diaminopyrimidine and 1,3-Diaminobenzene as nitrogen source initiated by hydrogen peroxide and ammonium persulfate as sulfer source respectively. The results demonstrate that nitrogen atoms in the six-membered rings of three precursors play a critical role on the formation of N-doping types and synergistic effects of N and S dopants in their derived carbon nanoshperes for ORR. Among the three precursors, 2,6-Diaminopyrimidine prefers to form the Pyridinic N doped carbon, resulting in the highest activity for ORR in N doped nanospheres, in contrast, 2,6-Diaminopyridine facilitates the formation of more content of Graphitic-N dopant, which has stronger synergy with thiophenic-S dopant in carbon matrix than that of Pyridinic N dopants. This unique characteristic endows 2,6-Diaminopyrimidine derived N, S co-doped nanospheres with excellent ORR activity of higher half-wave potential of 0.87 V vs. RHE in 0.1 M KOH and Zn-Air battery power output performance than that of the same loading of commercial Pt/C catalyst. Revealing the dependence of specific active sites determined by precursors with very similar molecular structures in the work will shed light on the precise design strategy based on the precursors-selecting guidance for the development of advanced multi-heteroatom doped carbon ORR catalysts. [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]

• Fe-N doped carbon catalyst was prepared by gelatin crosslinking in CaCl 2 solution. • Fe-NHHPC-900 showed a short-range aligned honeycomb hierarchical porous structure. • The microtopography and length of aligned pore can be controlled. • It had a large specific surface area with abundant mesoporous structure. • It displayed excellent ORR catalytic activity and SCs performance. The preparation of low-cost, high-efficiency and stable oxygen reduction reaction (ORR) catalysts is highly anticipated but remains a challenge. Herein, a novel strategy of CaCl 2 solution inducing gelatin crosslinking and acting as aligned pore template was put forward for preparation of Fe-N doped aligned hierarchical porous carbon. Furthermore, the microtopography and length of aligned pore can be controlled by adding NaCl solution. The prepared catalyst exhibited short-range aligned honeycomb hierarchical porous structure with large specific surface area and highly homogeneous distribution of Fe-N x active sites (Fe-NHHPC-900). Notably, in addition to excellent durability in the alkaline electrolyte, Fe-NHHPC-900 possessed excellent ORR performance with positive half-wave potential of 0.86 V, superior to commercial Pt/C catalysts. As electrode materials of supercapacitors, Fe-NHHPC-900 also displayed a high specific capacitance, excellent rate performance and excellent stability. This work also proved that the unique aligned porous structure can effectively optimize catalyst activity and improve supercapacitor performance. [ABSTRACT FROM AUTHOR]

• A Fe ,N- doped graphene prepared by NH 3 plasma is reported. • The reduction of graphene oxide and Fe ,N- doping were achieved simultaneously after NH 3 plasma treatment. • The Fe ,N- doped graphene prepared by NH 3 plasma exhibits the high activity and durability for oxygen reduction reaction. • There is a large specific surface area and abundant pyridinic N of the sample treated by NH 3 plasma. To obtain a low cost and high performance non-noble metal catalysts and replace noble metal catalysts such as Pt-based catalysts in oxygen reduction reaction (ORR) are of a significant importance for sustainable energy conversion. A kind of Fe,N-doped graphene prepared by NH 3 plasma as a promising alternative was prepared. Various characterizations including XRD, TEM, XPS and BET were carried out. The results of XRD and XPS characterizations indicate that GO reduction and Fe ,N- doping were achieved simultaneously after NH 3 plasma treatment. There is a large amount of pyridinic N (up to 68.19% of the total nitrogen content) on the surface of Fe ,N- GO-P. Fe particle in Fe ,N- GO-P is so small that they cannot be found in the images of HRTEM. Compared with the Fe ,N- GO-C, Fe ,N- GO-P has a large specific surface area. Although the onset potential is negative, but it exhibits a high limiting current density and durability in alkaline medium. The mechanism of ORR on Fe ,N- GO-P has been revealed that is ,N- G a quasi-four electron reaction pathway Fe,N-GO-P mainly followed. [ABSTRACT FROM AUTHOR]

A novel in situ strategy to embed Co 9 S 8 nanoparticles into nitrogen and sulfur codoped hollow porous carbon (Co 9 S 8 @N-S-HPC) is achieved. The Co 9 S 8 @N-S-HPC can be used an efficient catalyst for both ORR and HER. The unique nanostructure and synergistic interactions between Co 9 S 8 and N-S-HPC play a crucial role to improve the electrocatalytic performance. • Co 9 S 8 @N-S-HPC is fabricated using a novel in situ formation approach. • Co 9 S 8 @N-S-HPC shows excellent electrocatalytic performance toward ORR and HER. • Synergistic effect of Co 9 S 8 and N-S-HPC improves the electrocatalytic performance. The oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) are critical processes for many energy conversion technologies, where efficient catalyst plays a key role in these reactions. Here we report a novel in situ strategy to embed Co 9 S 8 nanoparticles (NPs) into nitrogen and sulfur codoped hollow porous carbon (Co 9 S 8 @N-S-HPC). In this strategy, the ZIF-8 surface is firstly decorated by cobalt thiourea, and then coated with a shell of polymeric resorcinol-formaldehyde, followed by a high temperature pyrolysis treatment. The resulting Co 9 S 8 @N-S-HPC shows comparable catalytic activity for ORR compared with commercial 20 wt% Pt/C catalyst and superior long-term stability under alkaline conditions. Simultaneously, Co 9 S 8 @N-S-HPC also exhibits an excellent HER activity with low onset overpotential of 68 mV, a small Tafel slope of 78 mV per decade and a long-term durability in alkaline medium. First-principles calculations reveal that Co 9 S 8 particle can anchor in N-S-HPC via a Co-S bond and enhance the binding of Co 9 S 8 and N-S-HPC. The N-S-HPC can affect the electronic structure of supported Co 9 S 8 strongly. The combined experimental and theoretical investigation show the outstanding ORR and HER performances of Co 9 S 8 @N-S-HPC are attributed to its unique nanostructure and synergistic interactions between Co 9 S 8 NPs and N-S-HPC. [ABSTRACT FROM AUTHOR]

• Fe 3 Co@NG-C shows excellent ORR activity in alkaline solution. • Fe 3 Co@NG-C exhibits enhanced durability and tolerance to methanol. • The activity of Fe 3 Co@NG-C is determined by the strain in N-doped graphene. Nitrogen-doped graphene is a promising non-precious metal electrocatalyst for the oxygen reduction reaction (ORR). We report that distorted nitrogen-doped graphene layers encapsulating Fe 3 Co nanoparticles supported on carbon (Fe 3 Co@NG-C) display excellent activity toward ORR in alkaline media. Compared with a commercial Pt/C electrocatalyst at a loading of 80 μg Pt /cm2 on a rotating disk electrode, the Fe 3 Co@NG-C exhibits an onset potential positively shifted by 50 mV at 0.1 mA/cm2 and a nearly identical half-wave potential. The Fe 3 Co@NG-C has minimal activity degradation during accelerated durability testing and superior tolerance to methanol than commercial Pt/C. Density functional theory calculations combined with poisoning experiments reveal that the high activity of the Fe 3 Co@NG-C mainly arises from strain in nitrogen-doped graphene induced by encapsulation of Fe 3 Co nanoparticles with exposed (1 1 0) planes, which promotes stabilization of the key OOH* intermediate involved in ORR. Our study shows the rational design of improved carbon-based electrocatalysts for ORR can be achieved by using strain engineering. [ABSTRACT FROM AUTHOR]

• Fe-N-C catalyst was prepared using FePc, dicyandiamide and CDC/graphene composite. • DCDA helps to mitigate metal agglomeration and boosts Fe-N x active site formation. • FeN-CDC/G/DCDA catalyst (E 1/2 = 0.76 V) outperforms FeN-CDC/G catalyst (E 1/2 = 0.70 V) • RRDE results display good selectivity for 4e− ORR pathway of FeN-CDC/G/DCDA (n = 3.9) The focus in the development of catalysts doped with transition metals aims to replace platinum group metal catalysts in fuel cells. However, these non-precious metal catalysts exhibit limited performance in acidic environment for the oxygen reduction reaction (ORR) due to issues such as metal agglomeration and the subsequent loss of active sites. Herein, we synthesised catalysts doped with iron and nitrogen on a composite material consisting of carbide-derived carbon (CDC) and graphene (G), employing an additional nitrogen source dicyandiamide (DCDA), denoted as FeN-CDC/G/DCDA. Our physico-chemical analysis unveiled that the inclusion of DCDA was effective in mitigating metal agglomeration during the synthesis process and increasing the presence of Fe-N x sites in the catalysts. Notably, the FeN-CDC/G/DCDA catalyst exhibited enhanced ORR activity in acid media with half-wave potential (E 1/2) of 0.76 V, surpassing the performance of the FeN-CDC/G catalyst, which had an E 1/2 value of 0.70 V. Furthermore, the rotating ring-disk electrode results indicated a reduced formation of hydrogen peroxide when employing the FeN-CDC/G/DCDA catalyst. The findings from this study represent a significant step towards the development of efficient catalysts for fuel cells, underscoring the pivotal role of additional nitrogen doping and its positive impact on the ORR performance. [ABSTRACT FROM AUTHOR]

Developing bifunctional catalysts to oxygen reduction (ORR) and oxygen evolution reactions (OER) is of vital to the practical application of rechargeable Zn-air batteries. Herein, an N-doped carbon-based catalyst (FeCo-NC-St) was prepared by using starch as a basic material which was transferred to defective carbon particles. The fresh starch-derived carbon is favor of the doping of nitrogen atoms to form more N-related ORR active sites. The existence of cobalt further positively regulates the OER activity of FeCo-NC-St. Resultantly, FeCo-NC-St shows 0.837 V of ORR E 1/2 and 1.611 V of OER E 10 which is slightly lower than the 0.850 V of ORR E 1/2 for Pt/C but far better than the 1.723 V of OER E 10 for the benchmark RuO 2 , revealing the superior bifunctional activities of FeCo-NC-St. Practically, the Zn-air battery with FeCo-NC-St outputs 1.505 V of open circuit voltage, 1.15–1.25 V of working voltage and 937.51 mW h g−1 Zn of specific energy density at 10 mA cm−2. The Zn-air battery also exhibits remarkable rechargeability and long-term durability, demonstrating the promising potential to substitute the precious Pt/Ru-based catalysts in the practical applications. An N-doped carbon-based catalyst (FeCo-NC-St) was prepared by using starch as a basic material. The resultant catalyst exhibits superior bifunctional catalytic activity to ORR and OER. [Display omitted] • An N-doped carbon-based bifunctional catalyst was fabricated. • Starch was utilized as a sustainable material. • The starch-derived carbon was favor of the doping of nitrogen atoms. • OER performance was positively regulated by cobalt element. • The catalyst exhibits satisfactory activity to ORR and OER. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis route: a straightforward, solvent-free, and one-step pyrolysis approach. • Well-dispersed tetragonal ZrO 2 , appropriate N dopants, and hierarchical pores. • Synergistic catalytic effect endow good ORR performance and high power density. An innovative, high-performance, non-noble-metal-based oxygen reduction reaction (ORR) catalyst must be developed utilizing a new and cost-effective technique. ZrO 2 has the merits of high stability, low toxicity, good catalytic activity, and low enthalpy for atomic oxygen adsorption. However, the poor conductivity restricts its application as an ORR catalyst. Here, we successfully prepared ZrO 2 nanoparticles / nitrogen-rich two-dimensional carbon nanosheet composites as ORR catalysts using a straightforward, solvent-free, one-step pyrolysis approach. Due to the unique component and structure characteristics, ZrO 2 @N-C-900 demonstrates remarkable ORR performances in alkaline electrolytes, such as high half-wave potential (0.82 V vs. RHE), higher current density (J L = 6.4 mA cm−2), and outstanding long term stability (95 % for 36,000 s). Especially, when used in a Zn-air battery, ZrO 2 @N-C-900 exhibited a power density of 148 mW cm−2, exceeding that of 20 % Pt/C. [ABSTRACT FROM AUTHOR]

This work reveals the crucial role of compressive lattice strain for the effective modulation of electronic metal-support interaction, which provides valuable guidance to the rational design of advanced ORR catalysts by lattice strain engineering. [Display omitted] • A structurally ordered PtCo/NCS-5 catalyst is successfully synthesized by a facile natural ligand annealing strategy. • The effective coupling of PtCo and NCS is proven to be beneficial to the improvement of ORR activity. • The electronic interaction between PtCo and NCS is explored through both characterizations and DFT calculations. • The crucial role of compressive lattice strain for the enhanced electronic interaction of PtCo/NCS-5 is revealed. Atomically ordered intermetallic catalysts have great potential for catalyzing efficient oxygen reduction reaction (ORR), while the coupling of metal and support are not emphasized enough. Herein, we report an atomically ordered PtCo bimetallic catalyst coupled with N-doped ultrathin carbon shells (PtCo/NCS) for ORR by a facile natural ligand annealing strategy. The formed NCS prevents the high-temperature sintering of catalysts by physical confinement, and the coupling effect results in a stronger affinity between PtCo and NCS for PtCo/NCS. The optimal PtCo/NCS-5 exhibits more exceptional activity and durability, outperforming commercial Pt/C and Pt 3 Co/C catalysts (C-Pt 3 Co/C). It is proved that PtCo and NCS synergically account for the enhanced ORR performance for PtCo/NCS-5. More importantly, the compressive lattice strain effectively promotes electron redistribution and optimizes the electronic structure for PtCo/NCS-5. This work further deepens the understanding of catalytic mechanisms and provides new insight into the rational design of advanced electrocatalysts toward ORR. [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]

Carbon fiber (CF), soybean dregs (SDs)/graphitic carbon nitride (g-C 3 N 4) derived carbon (denoted as CS) are used as complex carbon sources to prepare Fe and N co-doped carbon composites (Fe–N/CF-CS), through a simple solid grinding followed by thermal decomposition. The proportion of CF and CS clearly influences the morphology/structure and further the oxygen reduction reaction (ORR) behavior of the obtained Fe–N/CF-CS materials. The optimized Fe–N/CF-CS-2 catalyst possesses hierarchical porous structure, high surface area, and large pore volume, which benefits the electron/mass transfer process and the exposure of more active sites, and thus exhibiting the excellent ORR activity which can compete with commercial Pt/C. Meanwhile, the catalyst also presents superior methanol resistance and long term stability in ORR process. Carbon fiber, soybean dregs, and graphitic carbon nitride were used as complex carbon sources to prepare hierarchically porous iron and nitrogen co-doped carbon composite (Fe–N/CF-CS). The optimized catalyst exhibits ORR activity comparable with that of commercial Pt/C, and superior methanol tolerance than that of Pt/C. Image 1 • An eco-friendly method to prepare iron and nitrogen co-doped carbon towards ORR. • Carbon fiber, soybean dregs and g-C 3 N 4 are used as complex carbon sources. • The optimal Fe–N/CF-CS catalyst exhibits superior ORR performance. [ABSTRACT FROM AUTHOR]

Carbon-based metal-free nanomaterials have attracted immense and persistent attention as electrocatalysts for oxygen reduction reaction (ORR) in fuel cells, due to their high electrocatalytic activity, long-term stability and low cost. Here, a facile hydrothermal treatment in the presence of ammonium hydroxide (NH 4 OH) and sodium sulfide (Na 2 S), as precursors, has been developed to synthesize heteroatom-doped graphene quantum dots (GQDs). For comparison, undoped graphene quantum dots (GQDs), nitrogen doped graphene quantum dots (N-GQDs), sulfur doped graphene quantum dots (S-GQDs) and nitrogen and sulfur co-doped graphene quantum dots (N,S-GQDs) have been synthesized with the same method. The as-obtained N,S-GQDs possess a high N-doping content up to 9.36% and low S-doping content up to 0.78%, with a uniform size distribution similar to that of GQDs, N-GQDs and S-GQDs. Interestingly, the multi-types of N C or C S C bonding in metal free N,S-GQDs can significantly enhance the electrocatalytic activity for the oxygen reduction reaction (ORR), with the electron transfer number as good as 3.82, which verify the importance of our facile synthesis method to fabricate metal-free electrocatalysts for ORR and other electrochemical applications. Image 1 • We have successfully fabricated inexpensive hybrid compound, N,S-GQDs/rGO, by facile two-step hydrothermal process. • The N,S-GQDs have high N-content (9.36%) and low S content (0.78%). • The pyridinic-N and thiophene S play an important role for enhancing electrocatalytic activity. • The N,S-GQDs/rGO shows high electrocatalytic performance for ORR, with the electron transfer number as good as 3.82. [ABSTRACT FROM AUTHOR]

Graphical abstract N-, O- and P-tridoped hollow carbons (NOPHCs) were successfully synthesized via pyrolysis of Co 2 P-containing polypyrrole (Co 2 P@PPY) precursors, and the subsequent removal of Co 2 P templates. Thanks to the synergistic effect of the multi-heteroatoms doping in the carbon framework and the large density of electrochemically active sites on the surface of hollow carbon, these metal-free materials have been proven to show remarkable performance toward both hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) in alkaline media with excellent stability. Highlights • N-, O- and P-doped hollow carbons (NOPHCs) were successfully synthesized. • The materials were synthesized with the assistance of Co 2 P nanoparticles templates. • NOPHCs served as metal-free bifunctional electrocatalysts for HER and ORR. • The hollow structures gave large density of catalytically active sites for electrocatalysis. • Multi-heteroatoms dopants provided beneficial synergistic effects for modulating the adsorption of H 2 O and O 2 on the sites. Abstract To realize clean and renewable energy conversion systems, such as fuel cells and water splitting devices, cost-effective and energy-efficient bifunctional metal-free electrocatalysts are highly needed. Herein, N-, O- and P-doped hollow carbons (NOPHCs) are successfully synthesized via pyrolysis of Co 2 P-containing polypyrrole (Co 2 P@PPY) precursors and removal of Co 2 P templates. The materials are proven to serve as efficient and stable metal-free bifunctional electrocatalysts toward hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) in basic media. Notably, NOPHC 10 -900, which is obtained using 0.10 g of Co 2 P as template and pyrolyzed at 900 °C, exhibits high electrocatalytic performance for HER with a small overpotential of 290 mV at −10 mA cm−2, a low Tafel slope of 102 mV dec-1, and a great long-term stability for 19 h. Moreover, it affords decent electrocatalytic performance for ORR, with positive onset potential, high electron-transfer number, good methanol crossover tolerance and outstanding durability. The excellent electrocatalytic performance is mainly due to the synergistic effect of the multi-heteroatoms dopants in it and the large density of active sites on the surface of the hollow carbons. [ABSTRACT FROM AUTHOR]

Efficient catalyst for the oxygen reduction reaction (ORR) is of significance in the development of fuel cell and metal-air battery technologies. Heteroatom doped carbon materials have been considered as one of most promising alternatives to Pt-based catalysts. In this work, we exploit a nitrogen and sulfur dual-doped one-dimensional carbon rod catalyst with porous graphene-like layers on the surface derived from a Ni based metal-organic framework (MOF). The Ni-NSPC-6 catalyst with uniform distribution of N and S atoms in the carbon skeleton possesses a porous structure and a considerable specific surface area. Benefited from the special one-dimensional morphology, the convenient channel provided by the porous structure, the synergistic effect from the homogeneous co-doping of N and S, and the existence of proper amount of Ni 3 S 2 , the Ni-NSPC-6 affords a remarkable electrocatalytic performance toward ORR, including positive onset and half-wave potentials, a high catalytic current density, a low Tafel slope for oxygen reduction reaction and a remarkable ORR durability. The controllable synthesis of MOF derived S, N co-doped carbon materials with porous nanostructure will offer prospects in developing high performance electrocatalysts. Schematic illustration for the formation of Ni-NSPC-6 electrocatalyst and application for ORR. Image 1 • A nitrogen and sulfur dual-doped one-dimensional carbon rod catalyst was successfully prepared by pyrolyzing a Ni based MOF. • Graphene-like layers with abundant of mesopores are uniformly and compactly distributed on the surface of Ni-NSPC-6. • A negative shift of only 29.9 mV exists in the electrochemical half-wave potential between Ni-NSPC-6 and Pt/C. • The Ni-NSPC-6 exhibits an excellent ORR durability and a quasi-four-electron oxygen reduction pathway. [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]