Nitrogen-doped Carbon Electrocatalysts Research Articles

Three-dimensional porous structured cobalt- and nitrogen-doped carbon nanotube electrocatalyst derived from cobalt-based zeolitic imidazolate framework nanoleaves for high performance zinc-air battery

The development of efficient and cost-effective electrocatalysts to overcome the intrinsic sluggish kinetics of the oxygen reduction reaction (ORR) in zinc-air batteries is crucial. In this study, we introduce a strategy that integrates a template-assisted synthesis with subsequent thermal treatment to fabricate an active and stable cobalt-based nitrogen-doped carbon electrocatalyst, denoted as Co-N-CNT. The strategy adjusts the disordered architecture of the zeolitic imidazolate framework (ZIF) through the synergistic effect of bimetallic species, restricted the growth of zeolitic imidazolate framework nanoleaves (ZIF-L) using salt templates, and directed the transformation from a two-dimensional blade-like morphology to a three-dimensional multi-tiered composite structure. Notably, the Co-N-CNT-800 sample, synthesized at an optimized pyrolysis temperature of 800 °C, exhibits a half-wave potential of 0.89 V and demonstrates stability with sustained cycling over 21 h, which is comparable to the performance of commercial Pt/C electrocatalysts. Moreover, when employed as the cathode in zinc-air batteries, Co-N-CNT-800 not only surpasses Pt/C in terms of power density but also exhibits long-term charge/discharge stability. This findings offer a viable pathway for the design of active and cost-effective ORR electrocatalysts, holding promise for applications in the electrochemical energy storage and conversion systems.

Embedded metal inducing electron accumulation of multi-mesoporous pyridinic-N doped carbon for enhancing *COOH adsorption in electrochemical CO2 reduction

Nitrogen-doped carbon (NC) for carbon dioxide reduction reaction (CO2RR) are promising candidates. However, its selectivity and activity are limited by the undeveloped pore and limited electronic effect. Herein, we propose a strategy of three birds with one stone to utilize the embedded nickel for inducing electron-rich pyridinic-NC with multimodal porous structure based on the hard template assisted sacrificial template method. Nickel acts as sacrificial agent and inducer to facilitate the formation of mesoporous and reactive nitrogen species for capturing and activating reactants, respectively. Besides, we find that nickel as electron donor endows the NC with electron accumulation for participating actively in PCET reaction. The resultant Ni0.87-NC-1-AE exhibits an eminent FECO of 97.6 % with excellent activity and stability. In-situ Raman spectroscopy and the projected crystal orbital Hamilton populations (pCOHP) confirm the accumulation of *COOH and the stable adsorption of *COOH on the surface. What’s more, the well-designed experiments and DFT calculations accurately locate pyridinic-N as the active site, where the aggregated electrons donated by nickel significantly reduce the energy barrier of rate-determining step and promote the desorption of CO. This work provides an instructive perspective to construct advanced NC electrocatalysts with high mass transfer efficiency and high catalytic activity.

Unveiling the origin of activity in RuCoOx-anchored nitrogen-doped carbon electrocatalyst for high-efficiency hydrogen production and hydrazine oxidation using Raman spectroscopy

Hydrazine-assisted water electrolysis has gained much attention nowadays as an energy-saving strategy for the large-scale production of hydrogen fuel. Regardless, the synthesis of highly proficient bifunctional electrocatalysts remains a major challenge. Metal–organic frameworks (MOF) derived electrocatalysts have recently demonstrated excellent bifunctional activity in water electrolysis. Herein, we developed a new type of Ru-MOF on rod-like Co-MOF (Ru/Co-MOF) microstructures via a two-step solvothermal route. Subsequently, the Ru/Co-MOF was used as a precursor and self-template to synthesize an electrocatalytically active RuO2/Co3O4 anchored nitrogen-doped carbon (RuCoOx@NC) composite via a one-pot pyrolysis–oxidation strategy under atmospheric air. The RuCoOx@NC composite showed an ultralow overpotential of 44 mV for the hydrogen evolution reaction and 255 mV for the oxygen evolution reaction at 10 mA cm−2 in a 1 M KOH solution. Besides, the RuCoOx@NC composite exhibited an ultra-small working potential of − 0.040 V (vs. reversible hydrogen electrode (RHE)) for the hydrazine oxidation reaction at 10 mA cm−2 in a 1 M KOH/0.5 M hydrazine solution. The assembled RuCoOx@NC∥RuCoOx@NC membrane-free overall hydrazine splitting electrolyzer only required ultralow cell voltages of 0.063 and 0.505 V to produce 10 and 100 mA cm−2, with remarkable long-term stability, demonstrating its exceptional bifunctional activity. Ex situ Raman spectroscopy results indicate that both Co3O4 and RuO2 species contribute to the electrocatalytic activity of the RuCoOx@NC composite. This work suggests a potential strategy for developing bifunctional electrocatalytic materials for energy-saving hydrogen production to solve future energy demands.

Open-Mouthed Hollow Carbons: Systematic Studies as Cobalt- and Nitrogen-Doped Carbon Electrocatalysts for Oxygen Reduction Reaction.

Although hollow carbon structures have been extensively studied in recent years, their interior surfaces are not fully utilized due to the lack of fluent porous channels in the closed shell walls. This study presents a tailored design of open-mouthed particles hollow cobalt/nitrogen-doped carbon with mesoporous shells (OMH-Co/NC), which exhibits sufficient accessibility and electroactivity on both the inner and outer surfaces. By leveraging the self-conglobation effect of metal sulfate in methanol, a raspberry-structured Zn/Co-ZIF (R-Zn/Co-ZIF) precursor is obtained, which is further carbonized to fabricate the OMH-Co/NC. In-depth electrochemical investigations demonstrate that the introduction of open pores can enhance mass transfer and improve the utilization of the inner active sites. Benefiting from its unique structure, the resulting OMH-Co/NC exhibits exceptional electrocatalytic oxygen reduction performance, achieving a half-wave potential of 0.865V and demonstrating excellent durability.

Pyridine Functionalized Carbon Nanotubes: Unveiling the Role of External Pyridinic Nitrogen Sites for Oxygen Reduction Reaction.

Pyridinic nitrogen has been recognized as the primary active site in nitrogen-doped carbon electrocatalysts for the oxygen reduction reaction (ORR), which is a critical process in many renewable energy devices. However, the preparation of nitrogen-doped carbon catalysts comprised of exclusively pyridinic nitrogen remains challenging, as well as understanding the precise ORR mechanisms on the catalyst. Herein, a novel process is developed using pyridyne reactive intermediates to functionalize carbon nanotubes (CNTs) exclusively with pyridine rings for ORR electrocatalysis. The relationship between the structure and ORR performance of the prepared materials is studied in combination with density functional theory calculations to probe the ORR mechanism on the catalyst. Pyridinic nitrogen can contribute to a more efficient 4-electron reaction pathway, while high level of pyridyne functionalization result in negative structural effects, such as poor electrical conductivity, reduced surface area, and smallpore diameters, that suppressed the ORR performance. This study provides insights into pyridine-doped CNTs-functionalized for the first time via pyridyne intermediates-as applied in the ORR and is expected to serve as valuable inspiration in designing high-performance electrocatalysts for energy applications.

Highly efficient production of hydroxyl radicals from oxygen reduction over Ni-Fe dual atom electrocatalysts for removing emerging contaminants in wastewater

Advanced oxidation process (AOP) based on hydroxyl radicals (•OH) produced from electrocatalytic oxygen reduction reaction (ORR) is regarded as a promising technique for treating industrial wastewater. However, the poor efficiency of •OH production considerably limits the •OH-based AOP efficiency. In this study, a high-efficiency production of •OH from oxygen reduction is realized over Ni-Fe dual atom supported on nitrogen-doped carbon electrocatalysts (Ni0.5–Fe0.5–NC), where the O2 is preferentially adsorbed onto Ni sites. With the aid of neighboring electron-rich Fe atoms, the 2-electron intermediate *H2O2 over Ni sites is inclined to gain one electron to produce •OH (ΔG = -2.69 eV) rather than desorb to form H2O2 (ΔG = -1.05 eV). Even when hydrogen peroxide is produced by desorption, it is quickly activated to generate •OH by neighboring electron-rich Fe atoms. The in-situ produced •OH on Ni0.5–Fe0.5–NC reaches up to 4.61 mmol L−1 min−1 gcat−1, presenting the state-of-the-art AOP. Some emerging refractory contaminants (florfenicol, thiamphenicol, bisphenol A, phenol, sulfamethoxazole, and tetracycline hydrochloride) in wastewater can be fast and deep removed in the proposed AOP system based on ORR (C0 = 20 mgL−1, pH 7, −0.5 V vs SCE, working electrode: 6 cm2 carbon paper loading 6.0 mg catalyst). This study provides an ORR catalyst design inspiration for energetic and green generation of •OH, which would supply a reliable method for the development of wastewater treatment technology.

Balancing Mass Transfer and Active Sites to Improve Electrocatalytic Oxygen Reduction by B,N Codoped C Nanoreactors.

Mass transfer is critical in catalytic processes, especially when the reactions are facilitated by nanostructured catalysts. Strong efforts have been devoted to improving the efficacy and quantity of active sites, but often, mass transfer has not been well studied. Herein, we demonstrate the importance of mass transfer in the electrocatalytic oxygen reduction reaction (ORR) by tailoring the pore sizes. Using a confined-etching strategy, we fabricate boron- and nitrogen-doped carbon (B,N@C) electrocatalysts featuring abundant active sites but different porous structures. The ORR performance of these catalysts is found to correlate with diffusion of the reactant. The optimized B,N@C with trimodal-porous structures feature enhanced O2 diffusion and better activity per heteroatomic site toward the ORR process. This work demonstrates the significance of the nanoarchitecture engineering of catalysts and sheds light on how to optimize structures featuring abundant active sites and enhanced mass transfer.

Atomically Dispersed Metal–Nitrogen–Carbon Catalysts with d-Orbital Electronic Configuration-Dependent Selectivity for Electrochemical CO2-to-CO Reduction

A variety of atomically dispersed transition-metal-anchored nitrogen-doped carbon (M–N–C) electrocatalysts have shown encouraging electrochemical CO2 reduction reaction (CO2RR) performance, with the underlying fundamentals of central transition-metal atom determined CO2RR activity and selectivity yet remaining unclear. Herein, a universal impregnation-acid leaching method was exploited to synthesize various M–N–C (M: Fe, Co, Ni, and Cu) single-atom catalysts (SACs), which revealed d-orbital electronic configuration-dependent activity and selectivity toward CO2RR for CO production. Notably, Ni–N–C exhibits a very high CO Faradaic efficiency (FE) of 97% at −0.65 V versus RHE and above 90% CO selectivity in the potential range from −0.5 to −0.9 V versus RHE, much superior to other M–N–C (M: Fe, Co, and Cu). With the d-orbital electronic configurations of central metals in M–N–C SACs well elucidated by crystal-field theory, Dewar–Chatt–Duncanson (DCD) and differential charge density analysis reveal that the vacant outermost d-orbital of Ni2+ in a Ni–N–C SAC would benefit the electron transfer from the C atoms in CO2 molecules to the Ni atoms and thus effectively activate the surface-adsorbed CO2 molecules. However, the outermost d-orbital of Fe3+, Co2+, and Cu2+ occupied by unpaired electrons would weaken the electron-transfer process and then impede CO2 activation. In situ spectral investigations demonstrate that the generation of *COOH intermediates is favored over Ni–N–C SAC at relatively low applied potentials, supporting its high CO2-to-CO conversion performance. Gibbs free energy difference analysis in the rate-limiting step in CO2RR and hydrogen evolution reaction (HER) reveals that CO2RR is thermodynamically favored for Ni–N–C SAC, explaining its superior CO2RR performance as compared to other SACs. This work presents a facile and general strategy to effectively modulate the CO2-to-CO selectivity from the perspective of electronic configuration of central metals in M–N–C SACs.

CoFe nanoalloys encapsulated in nitrogen-doped carbon for efficient nitrite electroreduction to ammonia.

Electrochemical nitrite (NO2-) reduction to ammonia (NH3) can not only remove harmful NO2- in wastewater, but also produce valuable NH3. Herein, a CoFe nanoalloy encapsulated in nitrogen-doped carbon (CoFe-NC) electrocatalyst was fabricated for nitrite reduction, which achieved a high NH3 Faraday efficiency of 94.5%, and a large NH3 yield of 4050.6 μg h-1 cm-2 in a neutral electrolyte.

Trace Mn decorating nitrogen-doped carbon electrocatalysts for self-powered bio-electro-fenton cells toward simulated wastewater treatment

A self-aerated air-diffusion-floating electrode based on trace Mn decorating nitrogen-doped carbon electrocatalysts for simulated wastewater treatment in bio-electric-Fenton cells.

Atomic metal coordinated to nitrogen-doped carbon electrocatalysts for proton exchange membrane fuel cells: a perspective on progress, pitfalls and prospectives.

Proton exchange membrane fuel cells require reduced construction costs to improve commercial viability, which can be fueled by elimination of platinum as the O2 reduction electrocatalyst. The past 10 years has seen significant developments in synthesis, characterisation, and electrocatalytic performance of the most promising alternative electrocatalyst; single metal atoms coordinated to nitrogen-doped carbon (M-N-C). In this Perspective we recap some of the important achievements of M-N-Cs in the last decade, as well as discussing current knowledge gaps and future research directions for the community. We provide a new outlook on M-N-C stability and atomistic understanding with a set of original density functional theory simulations.

Electrochemical Generation of Catalytically Active Edge Sites in C2 N-Type Carbon Materials for Artificial Nitrogen Fixation.

The electrochemical nitrogen reduction reaction (NRR) to ammonia (NH3 ) is a potentially carbon-neutral and decentralized supplement to the established Haber-Bosch process. Catalytic activation of the highly stable dinitrogen molecules remains a great challenge. Especially metal-free nitrogen-doped carbon catalysts do not often reach the desired selectivity and ammonia production rates due to their low concentration of NRR active sites and possible instability of heteroatoms under electrochemical potential, which can even contribute to false positive results. In this context, the electrochemical activation of nitrogen-doped carbon electrocatalysts is an attractive, but not yet established method to create NRR catalytic sites. Herein, a metal-free C2 N material (HAT-700) is electrochemically etched prior to application in NRR to form active edge-sites originating from the removal of terminal nitrile groups. Resulting activated metal-free HAT-700-A shows remarkable catalytic activity in electrochemical nitrogen fixation with a maximum Faradaic efficiency of 11.4% and NH3 yield of 5.86µg mg-1 cat h-1 . Experimental results and theoretical calculations are combined, and it is proposed that carbon radicals formed during activation together with adjacent pyridinic nitrogen atoms play a crucial role in nitrogen adsorption and activation. The results demonstrate the possibility to create catalytically active sites on purpose by etching labile functional groups prior to NRR.

Tetrafunctional electrocatalyst for oxygen reduction, oxygen evolution, hydrogen evolution, and carbon dioxide reduction reactions

BackgroundThe development of novel electrocatalysts with high efficiency, low cost, and high stability to replace platinum group metal (PGM) electrocatalysts is essential for realizing sustainable energy applications. MethodsIn this study, we synthesized a tetrafunctional electrocatalyst comprising NiFe layered double-hydroxide (LDH) nanosheets anchored on carbon-nanotube-grafted (CNT), Co3O4-embedded, and N-doped porous carbon matrices (NC) derived from zeolitic imidazolate frameworks (NiFe LDHCNT-Co3O4/NC). Significant FindingsThis electrocatalyst exhibited superior performance to PGM electrocatalysts in the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and carbon dioxide reduction reaction (CO2RR). The linear sweep voltammetry study showed that the NiFe LDHCNT-Co3O4/NC demonstrated superior performance (Eonset = 0.85 V and E1/2 = 0.79 V for ORR; Ej=10 = 1.63 V for OER; overpotential = 0.84 V) comparing to the benchmarks of Pt/C and RuO2. A rechargeable Zn–air battery (ZAB) is used to verify the performance of the developed electrocatalyst in the ORR and OER; the ZAB exhibited an ultralow charge–discharge voltage gap (0.74 V) and excellent stability (104 cycles, >1600 h@10 mA cm−2). Overall water splitting (OWS) is performed to verify the performance of the developed electrocatalyst in the OER and HER. The adopted OWS device exhibited a long and stable process (1.6 V@10 mA cm−1, 700 h). CO2 conversion is investigated for evaluating the HER and CO2RR, and an 80% faradaic efficiency of CO production and high stability are obtained (166 mA cm−2@−1.09 V). We think that the synergistic effect of the NiFe LDHs, Co3O4 nanoparticles, and nitrogen-doped carbon electrocatalyst contributes to the excellent electrocatalytic performance of NiFe LDHCNT-Co3O4/NC in the aforementioned reactions. The hydrophilic NiFe LDHs and highly mesoporous carbon matrices provide a favorable ionic pathway for achieving rapid diffusivity and efficient mass transfer while the CNTs and carbon frameworks enhance the electrical conductivity during redox processes

CO2 Electroreduction on Mono- and Bi-Metallic M-N-C Catalysts

The production of syngas by traditional processes such as steam methane reforming is energetically expensive and leads to substantial CO2 emissions. This strongly motivates the development of CO2 electroreduction at ambient conditions. As a family of non-precious metal catalysts, transition metal-nitrogen-carbon electrocatalysts are cost effective and highly selective towards syngas production1,2. In this presentation, we will show our current research into mono and bi-metallic nitrogen-doped carbon (M-N-C, M = Fe, Mo or FeMo) electrocatalysts for syngas production. The electrocatalyst composition (i.e. the Fe:Mo ratio in the bimetallic electrocatalyst) was tuned, in combination with the potential applied, to control the selectivity and therefore the electrocatalyst’ ability to generate syngas. We show that a higher ratio of iron to molybdenum leads to an increase in selectivity to CO over H2 production. We show a greatly improved production rate for CO using traditional Fe-N-C which maxes out at a CO partial current density higher than that of commercial Ag nanoparticles (jco= -30.9 mA/cm2 geo at -1.1 VRHE) using a custom-built flow cell. The difficulties and importance of considering intrinsic catalytic activity is stressed to compare electrocatalytic activity. Apart from catalyst composition, reaction conditions can also substantially alter the electrochemical CO2/H2O co-electrolysis3. The catalyst composition can be used as an engineering control for the desired product selectivity by using a variable precursor metallic ratio in bi-metallic M-N-C catalysts. Potential control may be used alongside variations in reaction conditions for the dynamic control over the selectivity to syngas. Reference Delafontaine, L., Asset, T., & Atanassov, P. (2020). Metal–Nitrogen–Carbon Electrocatalysts for CO 2 Reduction towards Syngas Generation. ChemSusChem, 13(7), 1688–1698. Varela, A. S., Ranjbar Sahraie, N., Steinberg, J., Ju, W., Oh, H.-S., & Strasser, P. (2015). Metal-Doped Nitrogenated Carbon as an Efficient Catalyst for Direct CO2Electroreduction to CO and Hydrocarbons. Angewandte Chemie, 127(37), 10908–10912. Pan, F., & Yang, Y. (2020). Designing CO2 reduction electrode materials by morphology and interface engineering. Energy & Environmental Science, 13(8), 2275–2309. Figure 1

Carbon monoxide-resistant copper-cobalt nanocrystal@ nitrogen-doped carbon electrocatalysts for methanol oxidation reaction

The performance of direct methanol fuel cells (DMFC) mainly depends on the activity and stability of the noble-metal-based anode catalysts for methanol oxidation reaction (MOR), whose broad application is limited by the scarcity of noble metals and their susceptibility to carbon monoxide poisoning. Many efforts have been devoted to the developing of non-noble metal based MOR catalysts. Previous studies have shown that the catalytic properties of noble-metal catalysts can be modified by alloying in nanomaterials. However, non-noble metal-based nanocrystals are rarely studied as electrocatalysts, because of their high susceptibility to air oxidation. Herein, we report a simple strategy to prepare non-noble metal nanocrystals (Cu-Co nanocrystals), which are stabilized in a nitrogen-doped carbon (N-C) matrix to form Cu-Co@N-C composite. Since Co has a high activity for oxidation reactions, and Cu has a high adsorption capacity for methanol, the Cu-Co nanocrystals should present good MOR activity because of the synergistic effect of Cu and Co. The highly active Cu-Co nanocrystals are embedded in a porous N-C matrix with a large specific surface area (127.3 m2/g), which not only protects the Cu-Co nanocrystals, but also facilitate the mass and charge transfer. Indeed, the optimal Cu-Co@N-C catalyst shows a MOR activity of 171.3 mA/cm2 at 0.6 V vs SCE in alkaline medium, which is higher than most of previously reported Cu and Co-based MOR catalysts. The stability and CO-resistance of the optimal Cu-Co@N-C catalyst are also better than that of Pt/C catalyst, enabling Cu-Co@N-C a promising MOR catalyst for broad application of DMFC.

Highly performed nitrogen-doped porous carbon electrocatalyst for oxygen reduction reaction prepared by a simple and slight regulation in hydrolyzing process of ZIF-8

A simple and environmentally friendly method to prepare nitrogen-doped porous carbon (NPC) electrocatalysts for oxygen reduction reaction (ORR) is studied by using glucose (Glu) to regulate the hydrolyzing process and structure of ZIF-8 precursor. Compared with pristine ZIF-8, the ZIF-8 regulated by Glu (Glu/ZIF-8) has smaller particle size. NPC has a higher content of mesopores and macropores, a higher degree of graphitization, and a higher content of pyridine and graphitic nitrogen than nitrogen-doped carbon (CN) derived from prisitine ZIF-8. The onset potential, half-wave potential, and limiting current of NPC for ORR in 0.1 ​M KOH medium is 0.99 ​V, 0.88 ​V, and 5.43 ​mA ​cm−2, respectively. The electrocatalytic performance of NPC is similar to Pt/C, and better than CN. Furthermore, its stability and resistance to methanol are better than Pt/C. Its high electrocatalytic performance is attributed to the effect of Glu on the structure of ZIF-8 precursor.

Efficient oxygen reduction reaction by a highly porous, nitrogen-doped carbon sphere electrocatalyst through space confinement effect in nanopores

A highly porous nitrogen-doped carbon sphere (NPC) electrocatalyst was prepared through the carbonization of biomass carbon spheres mixed with urea and zinc chloride in N2 atmosphere. The sample carbonized at 1000 °C demonstrates a superior oxygen reduction reaction (ORR) performance over the Pt/C electrocatalyst, while its contents of pyridinic nitrogen and graphitic nitrogen are the lowest among samples synthesized at the same or lower carbonization temperatures. This unusual result is explained by a space confinement effect from the microporous and mesoporous structures in the microflakes, which induces the further reduction of peroxide ions or other oxygen species produced in the first step reduction to water to have the preferred overall four electron reduction ORR process. This work demonstrates that in addition to the amount or species of its active sites, the space confinement can be a new approach to enhance the ORR performance of precious-metal-free, nitrogen-doped carbon electrocatalysts.

Converting coals into carbon-based pH-universal oxygen reduction catalysts for fuel cells

Tapping into the potentialities of coals as valuable resources that can be transformed into state-of-the-art energy-related materials is now a burgeoning and fascinating research area, which accords with the clean utilization of coals. In the present work, coal-based porous nitrogen-doped carbon (CPNC) electrocatalysts toward the oxygen reduction reaction (ORR) at fuel cell cathodes have been easily prepared by the mechanochemistry-assisted strategy. Catalyst preparation combines the low-temperature pyrolysis with the high-temperature annealing, which guarantees nitrogen-containing substances sealed and confined in the carbon layers and skeletons and effectively converts them into nitrogen-relevant bonds, simultaneously regulating architectural features (e.g. specific surface areas, pore width distributions, defects and edges). The optimal metal-free CPNC electrocatalyst owns onset potentials of 0.97, 0.80 and 0.87 V, half-wave potentials of 0.84, 0.64 and 0.65 V, limiting current densities of 4.96, 4.60 and 4.90 mA cm−2, electron-transfer numbers of 3.93, 3.92 and 3.91, together with fine current stability and methanol tolerance, in 0.1 M KOH, 0.5 M H2SO4 and 0.1 M phosphate buffer solution (pH = 7.0), respectively. This is the first report on high-performance coal-based pH-universal oxygen reduction electrocatalysts, attributed to the effective trade-off between textural properties of catalysts (related to surface areas and pore structures) and the number of catalytic reaction sites (associated with nitrogen configuration distributions). Accordingly, this work has established the basis by which earth-abundant coals are readily converted into high-performance oxygen reduction carbonaceous electrocatalysts that are able to be integrated into various fuel cell test beds.

Nitrogen-doped hollow carbon polyhedron derived from salt-encapsulated ZIF-8 for efficient oxygen reduction reaction

The sluggish kinetics of oxygen reduction reaction (ORR) seriously restrains the practical implementation of fuel cells and metal-air batteries (MABs). While, Pt-based catalysts are well proven to be effective for the ORR process, they are rather expensive. Therefore, it is critical to developing low-cost and advanced catalysts with a rationally designed structure and abundant reactive sites as alternatives for Pt-based catalysts. Herein, nitrogen-doped hollow carbon polyhedrons (NHCP) have been fabricated by directly pyrolyzing ZIF-8, templated by NaCl. Benefiting from their hollow porous structure, large surface area, high graphitization degree and desired nitrogen bonding type, the as-synthesized NHCP exhibits exceptional ORR electrocatalytic activity with a half-wave potential (E1/2) of 0.86 V, high selectivity and outstanding long-term stability, exceeding most reported nitrogen-doped metal-free carbon electrocatalysts. Furthermore, the assembled Zn-air battery with NHCP cathode delivers a peak power density of 272 mW cm−2, a specific capacity of 740 mAh g−1 and an operation period of 160 h. This contribution provides a new avenue for designing high-performance electrocatalysts for ORR.

Chitosan-Derived Nitrogen-Doped Carbon Electrocatalyst for a Sustainable Upgrade of Oxygen Reduction to Hydrogen Peroxide in UV-Assisted Electro-Fenton Water Treatment

The urgency to move from critical raw materials to highly available and renewable feedstock is currently driving the scientific and technical developments. Within this context, the abundance of nat...