Superb Oxygen Reduction Reaction Research Articles

Designing highly efficient electrocatalyst for ORR and OER of transition metals doped g-C9N7: A density functional theory study

The application of fuel cells and metal-air batteries is limited by the rate of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Thus, the aim of this study is to find an efficient electrocatalyst to accelerate the reaction rate by DFT method. The structures of VIIB, VIII, IB, and IIB groups transition metals doped g-C9N7 as superb bifunctional electrocatalysts for ORR and OER are probed. The results show that Fe-, Pd-, and Au–C9N7 possess the superb ORR performance with the ORR overpotentials values of 0.35, 0.40, and 0.39 V, which gives them better performance than Pt(111). Moreover, Rh-, Pd-, and Pt–C9N7 have better OER performance with the OER overpotentials values of 0.30, 0.57, and 0.43 V, which makes them comparable to RuO2(110) and IrO2(110). Finally, the calculated bifunctional index (BI) results show that Pd–C9N7 can be used as an excellent bifunctional electrocatalyst because it has a minimum BI value of 0.97 V. This research has the potential to provide valuable theoretical direction into the use of M − C9N7 as electrocatalysts for both the ORR and OER.

Modulation in work function of CoTe as bifunctional electrocatalyst for rechargeable zinc air battery

The sluggish kinetics and inferior stability of oxygen electrocatalyst in rechargeable zinc air battery (ZAB) hamper its industrialization. In this work, we activate cobalt telluride (CoTe) by introduction of metallic cobalt (Co) to modulate the work function to facilitate the electron transfer from Co to CoTe during oxygen catalysis; additionally, the three-dimensional porous carbon nanosheets (3DPC) are invited to reduce the resistance towards electrolyte/oxygen diffusion. Thereby, Co-CoTe@3DPC only demands 280 mV overpotential to reach 10 mA cm−2 under alkaline oxygen evolution reaction (OER) condition, relatively lower than commercial iridium oxides (IrO2); besides, the operando electrochemical impedance spectroscopy (EIS) indicates a better resistance towards surface reconstruction than Co@3DPC leading to a superior stability. A Pt-like oxygen reduction reaction (ORR) performance, half-wave potential associated with kinetic current density, is achieved for Co-CoTe@3DPC. A maximum power density of 203 mW cm−2 is achieved and sustains for 800 h. Furthermore, the all-solid-state ZAB offers 97 mW cm−2. Theoretical calculation suggests that the incorporation of metallic Co to CoTe maintains the superb ORR activity and promotes the OER catalysis.

Construction of core‐shell heterostructured MnO@Co/NC for enhancing the oxygen electrocatalytic performance

AbstractThe development of non‐precious metal electrocatalysts for efficient oxygen reduction reaction (ORR) is a significant research field vital for the progress of zinc−air battery technology. Here, we purposely constructed a core‐shell heterostructured electrocatalyst consisting of MnO nanotubes covered by Co nanoparticles anchored on N‐doped carbon substrate. MnO@Co/NC displayed superior ORR capability with a half‐wave potential of 0.85 V and almost no potential decay after 10,000 cycles CV test, outform that of commercial Pt/C catalysts. Employing MnO@Co/NC as the air electrode catalyst in primary Zn−air batteries leads to a top power density of 145 mW cm−2 and an enhanced specific capacity of 869 mAh g−1 as compared to commercial noble metal catalysts. Such superb ORR performance outcomes primarily stem from the synergistic effect between Co/NC shell and MnO core since the coupling structure not only regulates the inherent electronic structure but also accelerates electron transfer speed and boosts the active sites. Besides, the Co/NC outer layer can also help to improve the corrosion resistance of MnO@Co/NC in the electrolyte. This work demonstrated that the core‐shell heterostructured non‐precious catalysts open up a new avenue for obtaining sufficiently effective ORR catalysts in Zn−air batteries and other related applications.

Hofmann-type MOFs derived intermetallic L10-PtFe/NC electrocatalysts for boosting oxygen reduction reaction

Intermetallic electrocatalysts have demonstrated significant potential in facilitating the cathodic oxygen reduction reaction (ORR) in fuel cells with enhanced activity and durability. However, it is still an enormous challenge to the facile synthesis of Pt-based intermetallic catalysts with uniform size and high ordering degree. Here, we innovatively fabricate the core-shell structured L10-PtFe intermetallics with Pt skins supported on N-doped porous carbon matrix through one-step pyrolysis of PtFe Hofmann-type metal-organic frameworks (denoted as L10-PtFe/NC). Under the constraints of the porous structure and cyano-ligand bonding, most Fe atoms are alloyed with Pt to form uniform-ordered PtFe intermetallics, while some Fe atoms are atomically dispersed in the carbon framework to form FeNx moieties. Notably, a series of intermetallic PtFe catalysts with different ordering degrees are successfully constructed by adjusting the pyrolysis temperature, which verified that the increase of ordering degree is beneficial to promote the electrocatalytic performance. In particular, the ordered L10-PtFe/NC-800 exhibits superb ORR activity with both mass and specific activities, which are 2.7-folds higher than those of commercial Pt/C. Moreover, after an accelerated durability test, L10-PtFe/NC-800 retains over 90 % mass activity. This work provides a promising approach for the development of efficient Pt-based intermetallic electrocatalysts for fuel cells.

A hierarchically ordered porous Fe, N, S tri-doped carbon electrocatalyst with densely accessible Fe-Nx active sites and uniform sulfur-doping for efficient oxygen reduction reaction

Doping FeNC catalysts with heteroatoms has been widely recognized as a most promising way to improve the electrocatalytic activity to achieve the replacement of Pt-based electrocatalysts for efficient oxygen reduction reaction (ORR). However, it is still a challenge to combine delicate control of the catalyst structure with heteroatom-doping to achieve optimal electrocatalytic efficiency. Herein, a strategy of combining chemical vapor deposition (CVD) with dual-template cooperative pyrolysis was rationally designed to synthesize the novel electrocatalyst with densely isolated single Fe atoms scattered on hierarchically ordered porous N and S codoped carbon (ISA-Fe/HOPNSC). The three-dimensional hierarchically ordered interconnected macro/mesoporous structure and uniform sulfur-doping make ISA-Fe/HOPNSC exhibit superb ORR performance in both alkaline and acidic electrolytes with a positive half-wave potential (0.920 V in 0.1 M KOH and 0.795 V in 0.5 M H2SO4) as well as outstanding methanol tolerance and long-time stability. As cathode catalyst in Zn-air battery, ISA-Fe/HOPNSC also provides much better maximum power density (210.7 mW cm−2) and specific capacity (796.7 mAh gZn−1) than those of Pt/C (112.6 mW cm−2 and 712.6 mAh gZn−1). Remarkably, the synthesis strategy in this work proposes myriad opportunities for combining delicate control of the catalyst structure with heteroatom doping to synthesize high-performance ORR catalysts.

Cobalt phosphide embedded N-doped carbon nanopolyhedral as an efficient cathode electrocatalyst in microbial fuel cells

Design and synthesis of effective and low-cost electrocatalysts for oxygen reduction reaction (ORR) is of great significance for the performance of microbial fuel cells (MFCs). Herein, we fabricated a cobalt phosphide embedded N-doped carbon nanopolyhedral (CoP@N-C) by simultaneous phosphidation and carbonization of ZIF-67 under N2 atmosphere. The physical and chemical properties of the electrocatalysts were analyzed in detail by scanning electron microscope, transmission electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, Fourier transform infrared spectroscopy and N2 adsorption–desorption isotherms. Results showed that the CoP@N-C had a dodecahedral shape with cobalt, nitrogen and phosphorus incorporating in porous graphical carbon. CoP compound which had a strong electron capture capability and ORR activity was embedded within the electrocatalysts. Introducing of P increased the contents of pyridinic-N, Co2+/Co3+ couples and oxygen vacancies, which provided sufficient catalytic active sites for ORR. The increased metallic Co content and mesoporous/macroporous surface area ensured efficient electron and mass transfer during ORR. Rotating disk electrode measurement revealed that the CoP@N-C exhibited a high ORR catalytic activity comparable to Pt/C, and an efficient four-electron pathway during ORR. When fabricated into activated carbon air cathode, the optimized CoP@N-C produced a maximum power density of 2236.8 mW m−2 in MFCs, which was about 2 times that of the bare activated carbon control. In addition to the superb ORR performance, the cost of the CoP@N-C was only ∼1/3 of commercial Pt/C. This study suggests that CoP@N-C could be an attractive non-precious metal ORR electrocatalyst for the application in high-performance MFCs.

Cobalt‑nitrogen‑carbon nanotube co-implanted activated carbon as efficient cathodic oxygen reduction catalyst in microbial fuel cells

The low catalytic activity of activated carbon (AC) toward oxygen reduction reaction (ORR) in air cathode severely limits the electricity production of microbial fuel cells (MFCs). In this work, a novel cobalt‑nitrogen‑carbon nanotube co-implanted activated carbon catalysts ([email protected]) were prepared by growth of Co/Zn-based metal organic frameworks on AC followed by thermal pyrolysis. The [email protected] catalyzed ORR via an efficient four-electron pathway in pH-neutral medium, and exhibited superb ORR catalytic activity comparable to commercial Pt/C. As compared with pristine AC, implantation of Co, N and carbon nanotubes into [email protected] improved the ORR current density and exchange current density of air cathodes by 120% and 73% respectively. The maximum power density of MFCs achieved 2045 ± 43 mW m−2 by using the optimized [email protected] pyrolyzed at 850 °C, which was 65% higher than that of pristine AC. The superb ORR performance of [email protected] originated from the synergistic effect of abundant Co-Nx, Pyridinic-N and Graphitic-N active sites, high graphitization degree, well dispersed Co nanoparticles and improved micro-mesoporous coexistence structure, which enabled high ORR catalytic activity and rapid mass transfer at the three-phase boundary. This work provides a new routine for large-scale synthesis of highly-efficient ORR electrocatalysts based on AC and metal organic frameworks, which has promising potential for the application in practical MFCs.

Metal-free amino acid glycine-derived nitrogen-doped carbon aerogel with superhigh surface area for highly efficient Zn-Air batteries

Development of high-efficiency non-noble metal materials to substitute Pt-based catalysts for oxygen reduction reactions is crucial in the commercial viability of Zn-air batteries technology. Nitrogen doped carbons (NDCs) are highly appealing as promising candidates. This study reports a facile molten salt (MS) method to synthesize aerogel-like nitrogen doped carbon (NDC-MS). The eutectic mixture acting as combined solvent and porogen leads to the obtained porous materials with extremely large surface area (1548.6 m2 g−1) and relatively high pore volume. The unique aerogel-like structure with hierarchical structure, increased catalytic active sits, extended surface area and large pore volume is beneficial for enhancing oxygen reduction reaction (ORR) performance. The resultant NDC-MS displays a superb ORR catalytic activity with high half-wave potential of 0.88 V, which is one of the most effective figures in previous literature of metal-free catalysts. The superb ORR performance can also be evaluated by Zn–air batteries with satisfactory power density and long-term operation stability. Therefore, such an efficient and green synthetic strategy can open up a new avenue for a wide range of commercial application of heteroatom doped carbon materials in advanced energy technologies.

Nitrogen-Doped Ketjenblack Carbon Supported Co3O4 Nanoparticles as a Synergistic Electrocatalyst for Oxygen Reduction Reaction.

Developing a highly active and cost-effective cathode electrocatalyst with strong stability for oxygen reduction reaction (ORR) is extremely necessary. In this work, we reported a facile synthetic path to prepare a hybrid nanostructure formed of nitrogen-doped Ketjenblack carbon (N-KC) supported Co3O4 nanoparticles (Co3O4/N-KC), which could be used as a promising and stable electrocatalyst for ORR. Compared with the physical mixture of Co3O4 and N-KC and pure N-KC samples, the resulting Co3O4/N-KC nanohybrid afforded remarkably superb ORR activity with a half-wave potential of 0.82 V (vs. reversible hydrogen electrode, RHE) and a limiting current density of 5.70 mA cm−2 in KOH solution (0.1 M). Surprisingly, the Co3O4/N-KC sample possessed a similar electrocatalytic activity but better durability to the 20 wt% Pt/C catalyst. The remarkable ORR activity of the Co3O4/N-KC nanohybrid was mainly due to the strong coupling effect between Co3O4 and N-KC, the N species dopant, high electroconductivity, and the large BET surface area. Our work enlightens the exploitation of advanced Co3O4/carbon hybrid material alternative to the Pt-based electrocatalysts.

Nitrogen-doped braided-looking mesoporous carbonaceous nanotubes as an advanced oxygen reduction electrocatalyst

Exploring low-cost, high-active, durable electrocatalysts for oxygen reduction reaction (ORR) in fuel cells and metal-air batteries is highly desirable but remains a great challenge. In this work, with the application of a newly developed metal-free nanocasting method, an in-situ mesoporous nitrogen-doped braided-looking carbon nanotube (MNCNT) catalyst was fabricated. It was examined to possess a high specific surface area (828 m2g-1), and pores with the tunable size. The catalyst shows superb ORR activity with a half-wave potential (E1/2) of 0.77 V vs. RHE in alkaline medium, inferior to that of commercial 20 wt% Pt/C, but superior to those of 5 wt% Pt/C and most other metal-free catalysts reported in previous literature. Besides, a high limited current density of 3.9 mA cm−2 at 0.2 V vs. RHE is yielded, and strong methanol tolerance as well as good stability of such catalyst is observed. According to the comparable study, the high ORR activity can be attributed to the porous feature of such nanotubes, as it may engender more active sites for ORR (porous nature & more edges), and boost reactivity of the active sites (nitrogen-doping), compared with the general carbon nanotubes. This work may intrigue the inspiration to explore highly efficient metal-free and carbon-based electrocatalysts toward boosting ORR.

Migration-Prevention Strategy to Fabricate Single-Atom Fe Implanted N-Doped Porous Carbons for Efficient Oxygen Reduction.

It is highly desired but challenging to achieve highly active single-atom Fe sites from iron-based metal-organic frameworks (MOFs) for efficient oxygen reduction reaction (ORR) due to the easy aggregation of iron species and formation of the inactive Fe-based particles during pyrolysis. Herein, a facile migration-prevention strategy is developed involving the incorporation of polyaniline (PANI) into the pores of iron porphyrinic-based MOF PCN-224(Fe) and followed by pyrolysis to obtain the single-atom Fe implanted N-doped porous carbons material PANI@PCN-224(Fe)-900. The introduced PANI inside the pores of PCN-224(Fe) not only served as protective fences to prevent the aggregation of the iron species during thermal annealing, but also acted as nitrogen sources to increase the nitrogen content and form Fe-Nx-C active sites. Compared with the pristine PCN-224(Fe) derived carbonization sample containing Fe-based particles, the carbonaceous material PANI@PCN-224(Fe)-900 without inactive Fe-based particles exhibited superb ORR electrocatalytic activity with a more positive half-wave potential, significantly improved stability in both alkaline media, and more challenging acidic condition. The migration-prevention strategy provides a new way to fabricate atomically dispersed metal active sites via pyrolysis approach for promoting catalysis.

Three-Dimensional Biocarbon Framework Coupled with Uniformly Distributed FeSe Nanoparticles Derived from Pollen as Bifunctional Electrocatalysts for Oxygen Electrode Reactions.

The development of carbon-based catalysts with satisfactory performance for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is critical but challenging to achieve sustainable energy conversion and storage. Herein, a pollen biomass-derived carbon electrocatalyst with a three-dimensional porous framework, coupled with uniform distribution of FeSe nanoparticles, has been prepared by pyrolysis of the pollen precursor, followed by selenylation. The optimal catalyst FeSe/NC-PoFeSe exhibits a superb ORR activity with a half-wave potential of 0.86 V versus a reversible hydrogen electrode and OER activity with a low overpotential (330 mV at 10 mA cm-2) in alkaline media, compared with commercial Pt/C and IrO2/C catalysts, respectively. On the basis of the characterization results, we ascribe the enhanced ORR performance to sufficient Fe-N x, pyridinic N, and graphitic N and the excellent OER performance in the presence of FeSe nanoparticles uniformly mounted on the N-doped carbon materials. In addition, we believe that the coupling effect between the FeSe nanoparticles and biocarbon led to a further improvement in the electrochemical performance. Significantly, the prominent ORR and OER stability of FeSe/NC-PoFeSe shows great promise in renewable energy devices.

Facile synthesis of Co-N-rGO composites as an excellent electrocatalyst for oxygen reduction reaction

Cobalt and nitrogen co-doped reduced graphene oxide (Co-N-rGO) composites are prepared by a facile low-temperature hydrothermal method. Structure characterization reveals that cobalt and nitrogen are co-ordinately attached to the rGO sheets with the formation of covalent C-N and Co-O-C linkages. Cyclic voltammetry and linear sweep voltammetry show that the Co-N-rGO composite possesses higher electrocatalytic activity and four-electron selectivity for oxygen reduction reaction (ORR) as compared to the rGO, Co-rGO and N-rGO. In addition, the Co-N-rGO composite presents excellent stability and durability in alkaline medium comparable to commercial Pt/C. The edge plane CoN2/C, CoN4/C, and basal plane macrocyclic CoN4/C species within the Co-N-rGO structure are proposed to be the active sites performing catalysis in the ORR. The strong covalent linkages between the cobalt/nitrogen and rGO not only enable potent synergy of cobalt, nitrogen and rGO in catalysis, but also ensure structure stability of the composite. Due to the superior ORR activity of Co-N-rGO, high-temperature heat treatment is not able to improve its activity any more. The low-temperature hydrothermal method is anticipated to be used as a low-cost and facile preparation approach for ORR catalysts, and the superb ORR performance of Co-N-rGO endow it with great application potential in fuel cells, metal-air batteries and other ORR-related electrochemical industries.

Bimetallic Zeolitic Imidazolite Framework Derived Carbon Nanotubes Embedded with Co Nanoparticles for Efficient Bifunctional Oxygen Electrocatalyst

AbstractBifunctional oxygen catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) with high activities and low‐cost are of prime importance and challenging in the development of fuel cells and rechargeable metal–air batteries. This study reports a porous carbon nanomaterial loaded with cobalt nanoparticles (Co@NC‐x/y) derived from pyrolysis of a Co/Zn bimetallic zeolitic imidazolite framework, which exhibits incredibly high activity as bifunctional oxygen catalysts. For instance, the optimal catalyst of Co@NC‐3/1 has the interconnected framework structure between porous carbon and embedded carbon nanotubes, which shows the superb ORR activity with onset potential of ≈1.15 V and half‐wave potential of ≈0.93 V. Moreover, it presents high OER activity that can be further enhanced to over commercial RuO2 by P‐doped with overpotentials of 1.57 V versus reversible hydrogen electrode at 10 mA cm−2 and long‐term stability for 2000 circles and a Tafel slope of 85 mV dec−1. Significantly, the nanomaterial demonstrates better catalytic performance and durability than Pt/C for ORR and commercial RuO2 and IrO2 for OER. These findings suggest the importance of a synergistic effect of graphitic carbon, nanotubes, exposed Co–Nx active sites, and interconnected framework structure of various carbons for bifunctional oxygen electrocatalysts.

Enhancement of oxygen reduction reaction performance: The characteristic role of Fe[sbnd]N coordinations

Fe-Nx-C materials are extensively investigated due to their outstanding performance for oxygen reduction reaction (ORR). However, even though Fe3C, pyridinic N, and FeN coordinations have been widely recognized as active sites for catalyzing the ORR, there is almost no report about the dominating functional groups responsible for the enhancement of ORR performance, especially in acidic media. Here we developed a robust and universal non precious metal catalyst, Fe3O4 nanoparticles (particle size: ∼50 nm) embedded in 3D cross-linking hierarchically porous N-doped carbon (noted as Fe3O4@HPNC), as a superb ORR performance catalyst in both basic and acidic media. More importantly, in this hybrid there exists no Fe3C phase, which makes it easier to identify the prominent group contributing to the enhanced ORR performance. Taking into account that the enhancing factor of the ORR half-wave potential at Fe3O4-300@HPNC with respect to that at HPNC in acidic media (36.6%) is much higher than that in basic media (7.6%), it could be deduced that the role of the FeN coordinations for ORR in acidic media is more dominating than that in basic media. Optimized Fe3O4-300@HPNC exhibits comparable ORR activity in acidic, or even better in basic media, superior stability and MeOH tolerance compared with the commercial Pt/C.

Sustainable Route for Molecularly Thin Cellulose Nanoribbons and Derived Nitrogen-Doped Carbon Electrocatalysts

Ultrathin cellulose nanoribbons were extracted from earth-abundant biomass using 2,2,6,6-tetramethylpiperidine-1-oxyl-catalyzed (TEMPO-catalyzed) oxidation and sonication processes. By two TEMPO-oxide systems with different processing times, TEM and AFM observations indicate the obtained cellulose nanoribbons (Cel-NRs) with dimensions of 400–800 nm in length, 1.72–2.54 nm in width, and 0.78–2.67 nm in thickness. The dimension data indicate that the Cel-NRs from the TEMPO/NaBr/NaClO system are much shorter but contain more cellulose chains than those from the TEMPO/NaClO/NaClO2 system. Moreover, these abundant biomass nanoribbons were fabricated from direct pyrolysis with NH3 activation. The obtained highly active nitrogen-doped carbon nanoribbons (N-CNRs) and metal-free oxygen reduction reaction (ORR) electrocatalysts show superb ORR activity (half-wave potential of 0.71 and 0.73 V versus reversible hydrogen electrode) and high selectivity (electron-transfer number of 3.26 and 3.74 at 0.8 V), comparable c...

High-Performance Non-Noble Electrocatalysts for Oxygen Reduction Using Fluidic Acrylonitrile Telomer as Precursor

Non-noble-metal catalysts have shown promising oxygen reduction reaction (ORR) activity in proton exchange membrane fuel cells (PEMFCs). Herein, by using sulfur-terminated fluidic acrylonitrile telomere (ANT) as precursor, an N and S dual-doped Co/ANT/C catalyst was prepared via a facile heat treatment of the mixture of Co salt, ANT and carbon black, in which cobalt salt was uniformly-dispersed and interacted with ANT. As such, the increasing contact area between ANT and cobalt salt leads to a highly catalytic activity toward oxygen reduction reaction. Most importantly, by using ANT as precursor, the catalyst showed a remarkable improvement in the onset potential and current density as compared with those prepared from pure carbon black, cobalt salt/C or catalyst using high molecular weight polyacrylonitrile as precursor. Besides, the as-made Co/ANT/C catalyst demonstrated a comparable catalytic activity with commercial expensive Pt/C at high loading. In addition, the catalyst participated promotes a direct four-electron reduction of O2 to H2O and long term operation stability in an alkaline medium. Owing to its superb ORR performance, low cost and facile synthesis approach, such prepared Co/ANT/C catalyst has great potential applications in PEMFCs.

One-step preparation of N-doped graphene/Co nanocomposite as an advanced oxygen reduction electrocatalyst

N-doped graphene/Co nanocomposites (NG/Co NPs) have been prepared by a simple one-step pyrolysis of Co(NO3)2∙6H2O, glucose and dicyandiamide (DCDA). The products with nitrogen doped and suitable graphitic degree perform high electrocatalytic activity (with the reduction peak at −0.099V vs Ag/AgCl) and near four-electron selectivity for the oxygen reduction reaction (ORR), with excellent stability and durability in alkaline medium comparable to a commercial Pt/C catalyst. Owing to the superb ORR performance, low cost and facile preparation, the catalysts of NG/Co NPs have great potential applications in fuel cells, metal-air batteries and ORR-related electrochemical industries.

Advanced non-precious electrocatalyst of the mixed valence CoO x nanocrystals supported on N-doped carbon nanocages for oxygen reduction

Taking advantage of the nitrogen (N)-participation and large surface area of N-doped carbon nanocages (NCNCs), the CoO x nanocrystals are conveniently immobilized onto the NCNCs with high dispersion. The CoO x /NCNCs hybrid exists in the mixed valence with predominant CoO over Co3O4 and demonstrates superb oxygen reduction reaction activity and stability remaining ~94% current density even after operation over 100 h. These results suggest a promising strategy to develop advanced electrocatalysts with the novel NCNCs or even beyond.

One-step scalable preparation of N-doped nanoporous carbon as a high-performance electrocatalyst for the oxygen reduction reaction

N-doped porous carbon materials have been prepared by a simple one-step pyrolysis of ethylenediaminetetraacetic acid (EDTA) and melamine in the presence of KOH and Co(NO3)2·6H2O. The combination of the high specific area (1485 m2·g−1), high nitrogen content (10.8%) and suitable graphitic degree results in catalysts exhibiting high activity (with onset and half-wave potentials of 0.88 and 0.79 V vs the reversible hydrogen electrode (RHE), respectively) and four-electron selectivity for the oxygen reduction reaction (ORR) in alkaline medium—comparable to a commercial Pt/C catalyst, but far exceeding Pt/C in stability and durability. Owing to their superb ORR performance, low cost and facile preparation, the catalysts have great potential applications in fuel cells, metal-air batteries, and ORR-related electrochemical industries. Open image in new window