Efficient electrocatalyst of Pt–Fe/CNFs for oxygen reduction reaction in alkaline media

Transition metal iron-based catalysts are promising electrocatalysts for oxygen reduction reaction (ORR), and they have the potential to replace noble metal catalysts. The one-dimensional of carbon nanofibers with tubular structure can effectively promote the electrocatalytic activity, which facilitates electron transport. Herein, the Pt–Fe/CNFs were synthesized by electrospinning and subsequent calcination. Benefiting from the advantages of one-dimensional structure, Pt–Fe/CNFs-900 with fast electrochemical kinetics and excellent stability for ORR with excellent onset of 0.99 V, a low Tafel slope of 62 mV dec⁻¹ and high limiting current density of 6.00 mA cm⁻². Long-term ORR testing indicated that the durability of this catalyst was superior to that of commercial Pt/C in alkaline electrolyte. According to RRDE test, the ORR reaction process of Pt–Fe/CNFs-900 was close to four-electron transfer routes.     

A metal-organic framework-derived Fe–N–C electrocatalyst with highly dispersed Fe–Nx towards oxygen reduction reaction

Metal and nitrogen co-doped catalysts have been promising alternatives to platinum group metal (PGM) catalysts for oxygen reduction reaction (ORR) over the past few decades. Herein, we have synthesized an efficient Fe–N–C catalyst by the co-calcination of NH₂-MIL-101@PDA and melamine. The best Fe–N–C shows a positive half-wave potential of 0.844 V, which is 14 mV higher than that of Pt/C catalyst, as well as superior methanol resistance and long-term durability in alkaline electrolyte. In addition, Fe–N–C also exhibits pronounced catalytic activity and a direct 4e⁻ reaction pathway in acid electrolyte. We ascribed the excellent ORR performance of Fe–N–C to its crumpled structure, large specific surface area (584.6 m² g⁻¹) and high content of Fe-Nx sites (1.22 at. %). This study provides a simple way for the fabrication of excellent PGM-free ORR catalysts.     

Metallic iron doped vitamin B12/C as efficient nonprecious metal catalysts for oxygen reduction reaction

The development of efficient nonprecious metal catalysts for oxygen reduction reaction (ORR) is crucial but challenging. Herein, one simple and effective strategy is developed to synthesize bimetallic nitrogen-doped carbon catalysts by pyrolyzing Fe-doped Vitamin B12 (VB12) supported carbon black (Fe-VB12/C). A typical Fe₂₀-VB12/C catalyst with a nominal iron content of 20 wt% pyrolyzed at 700 °C exhibits remarkably ORR activity in alkaline medium (half-wave potential of 0.88 V, 10 mV positive than that of commercial Pt/C), high selectivity (electron transfer number > 3.93), excellent stability (only 6 mV negative shift of half-wave potential after 5000 potential cycles) and good methanol-tolerance. The superior ORR activity of the composite is mainly attributed to the improved mesoporous structure and co-existence of abundant Fe-N_x and Co-N_x active sites. Meanwhile, the metallic Fe are necessary for the improved ORR activity by means of the interaction of metallic Fe with neighboring active sites.     

Facile preparation of Fe3C decorate three-dimensional N-doped porous carbon for efficient oxygen reduction reaction

Novel Fe₃C nanoparticles that decorate three-dimensional N-rich porous carbon (Fe₃C@3DNC) catalysts were designed and synthesized by double templates assisted high-energy ball milling and subsequent high-temperature pyrolysis for the oxygen reduction reaction (ORR). NaCl and Na₂SiO₃ are used as the mixed template while Fe(NO₃)₃·9H₂O and 2-Methylimidazole were used as the iron, nitrogen and carbon sources. The optimized Fe₃C@3DNC catalyst (Fe₃C@3DNC-1-900) had good ORR performance in alkaline medium, with an Eonest value of 0.968 V and E_1/2 value of 0.861. In addition, the catalytic process exhibited selectivity–nearly four-electron transfer kinetics and possesses a lower Tafel slope compared to commercial Pt/C catalyst as well as good methanol tolerance. In addition, the Fe₃C@3DNC-1-900 catalyst also had excellent ORR activity (E_1/2 = 0.72 V) and long-term stability (the half-wave potential only occurs at 10 mV after 5000 cycles) in acidic media. The good catalytic performance of the Fe₃C@3DNC-1-900 catalyst can be attributed to the 3D hierarchically porous structure and extremely high number of active sites around the porous carbon. The double template assisted high-energy ball milling strategy can be a promising and scalable method to prepare three-dimensional porous carbon-based composite materials for energy conversion and storage applications.     

PtFe and Fe3C nanoparticles encapsulated in Fe–N-doped carbon bowl toward the oxygen reduction reaction

The high-temperature calcination strategy facilitates the formation of alloy atoms but inevitably results in the aggregation and deactivation of the metal particles for the oxygen reduction reaction (ORR) electrocatalysts. Herein, we report the successful encapsulation of Platinum–Iron (PtFe) nanoparticles (∼4.7 nm) in the N-doped hollow carbon hemisphere matrix (NCB) containing Fe–N and Fe₃C without employing high-temperature pyrolysis, which effectively facilitates the well-dispersed Pt nanoparticles and the formation of PtFe nanoalloys. The hollow carbon hemisphere structure contributes to the expansion of the specific surface area and exposure of active sites of the catalyst, meanwhile, the modification of the surface of the carbon nano-bowl from a predominantly Fe to a functional electrocatalyst with a primarily PtFe alloy can boost the ORR catalytic activity and stability. It is found that the Pt3Fe/Fe₃C-NCB catalyst exhibits the optimum ORR performance with a mass activity (0.97 A mg⁻¹_Pt), 5.10 times higher than the commercial Pt/C (0.19 A mg⁻¹_Pt). Pt3Fe/Fe₃C-NCB also displays excellent durability in comparison to the commercial Pt/C after 20,000 potential cycles. Combined with the Physical characterization and the electrochemical test results, Fe₃C-NCB plays a strong metal-support role for the encapsulated PtFe nanoparticles structure, thereby preventing nanoparticle migration and corrosion. Experimental characterization and theoretical calculations show that the appropriate PtFe alloy composition and the strain effect induced by Fe–N/Fe₃C active sites are sufficient to accelerate the detachment of oxygenated species from the alloy surface, resulting in a catalyst with excellent ORR performance.     

Fe3C nanoparticles decorated Fe/N codoped graphene-like hierarchically carbon nanosheets for effective oxygen electrocatalysis

Hierarchically porous carbon sheets decorated with transition metal carbides nanoparticles and metal-nitrogen coordinative sites have been proposed as the promising non-precious metal oxygen electrocatalysts. In this work, we demonstrate a facile and low-cost strategy to in situ form Fe/N codoped hierarchically porous graphene-like carbon nanosheets abundant in Fe-N_x sites and Fe₃C nanoparticles (Fe–N/C) from pyrolyzing chestnut shell precursor. The as-prepared Fe–N/C samples with abundant Fe-N_x sites and Fe₃C nanoparticles show superior electrocatalytic activity to oxygen reduction reaction (ORR) in the alkaline medium as well as high stability and methanol tolerance due to the integration of multi-factors: the high content of Fe-N_x active sites, the coexistence of Fe₃C, the unique hierarchically porous structure and high conductivity of carbon matrix. The optimal Fe–N/C-2-900 sample exhibits a more positive half-wave potential (−0.122 V vs. Ag/AgCl (3 M) reference electrode) than commercial 20 wt% Pt/C catalyst. This study provides a facile approach to synthesize Fe₃C nanoparticles decorated Fe/N co-doped hierarchically porous carbon materials for effective oxygen electrocatalyst.     

Hollow NH2-MIL-101@TA derived electrocatalyst for enhanced oxygen reduction reaction and oxygen evolution reaction

Non-precious metal-based electrocatalysts with excellent activity and stability are highly desired for the sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, a tannic acid (TA) etching strategy is used to inhibit the metal aggregation and achieve muti-metal doping. The hollow NH₂-MIL-101@TA derived Fe–N–C catalyst exhibits superior ORR catalytic activity with an E_1/2 of 0.872 V and a maximum output power density of 123.4 mW cm⁻² in Zn-air battery. Since TA can easily chelate with metal ions, Fe/Co–N–C and Fe/Ni–N–C are also synthesized. Fe/Ni–N–C manifests exceptional bifunctional activity with an E_j = 10 of 1.67 V and a potential gap of 0.833 V between E_j = 10 and E_1/2 in alkaline electrolyte, which is 45 mV smaller than Pt/C–IrO₂. The improvement of ORR and OER performance of the catalysts via the simple TA etching and chelation method provides a novel strategy for the design and synthesis of efficient electrocatalysts.     

In-situ synthesis of Fe,N, S co-doped graphene-like nanosheets around carbon nanoparticles with dual-nitrogen-source as efficient electrocatalyst for oxygen reduction reaction

Iron, nitrogen, sulfur co-doped Fe/N/C catalyst (poly-AT/Me–Fe/N/C) with the structure of graphene-like nanosheets around carbon nanoparticles were successfully synthesized for oxygen reduction reaction (ORR). 2-Aminothiazole and melamine were utilized as the dual-nitrogen-source. The results showed that 2-Aminothiazole, as the nitrogen and sulfur source, contributed to in-situ synthesizing graphene-like nanosheets around KJ-600 carbon nanoparticles with high specific surface area (1098 m²/g). Proper method to introduce melamine during the synthesis could increase the content of pyridinic-N and Fe-N_x moieties in the catalyst without changing the morphology. Due to the high surface area and high content of pyridinic-N and Fe-N_x moieties, the obtained poly-AT/Me–Fe/N/C catalyst exhibited high electrochemical activity and stability with the half-wave potential of 0.84 V (RHE) in 0.1 M NaOH solution, which is merely 17 mV lower than commercial Pt/C. The electron transfer number was 3.83, indicating a nearly 4e^? transfer for the ORR with low HO₂^? yield.     

A novel 3D hybrid carbon-based conductive network constructed by bimetallic MOF-derived CNTs embedded nitrogen-doped carbon framework for oxygen reduction reaction

The rational design of novel non-precious oxygen reduction reaction (ORR) electrocatalysts with good catalytic activity for energy conversion devices is under the spotlight of current research. Herein, we designed and fabricated a novel 3D Co-derived CNTs embedded nitrogen-doped carbon framework (denoted as Co-CNTs@NCF_T, where T represents the pyrolysis temperature) as an efficient ORR catalyst by pyrolysis of the bimetallic metal-organic framework (MOF) in the presence of graphene oxide (GO). The optimized catalyst furnishes large specific surface area, outstanding electrical conductivity and rapid mass transport rates during reactions. Because of these synergistic advantages, the Co-CNTs@NCF₉₀₀ exhibits excellent ORR catalytic activity in terms of a high onset potential of 0.96 V and a half-wave potential of 0.84 V in alkaline electrolyte, outperforming the commercial Pt/C. Furthermore, the Co-CNTs@NCF₉₀₀ manifests good stability and methanol tolerance comparable to the commercial Pt/C catalyst. The presented strategy open up a new avenue for the synthesis of novel electrocatalysts derived from MOF materials for energy-related applications.     

High-efficiency copper-based electrocatalysts for oxygen electroreduction by heating metal-phthalocyanine at superhigh temperature

The highly efficient Cu-based ORR catalysts (Cu–N–C) were obtained by the pyrolysis of mesoporous KIT-6 silica-supported phthalocyanines at superhigh temperature (1000 °C). The prepared Cu–N–C catalyst was demonstrated as one of the best Cu-based electrocatalysts for ORR, with 0.82 V half-wave potential in 0.1 M KOH and 0.72 V half-wave potential in 0.1 M HClO₄. It showed the competitive ORR activity to high-performance Fe- or Co-based carbon catalysts. Moreover, the ORR catalytic performance of Cu–N–C could be further enhanced by co-doping few Fe species (Fe–Cu–N–C) into the carbon framework. It revealed about 30 mV higher half-wave potential and better stability than Cu–N–C catalyst in both alkaline and acidic media. Cu–N–C and Fe–Cu–N–C electrocatalysts could be produced at a scale of over 15 g by facilely enlarging the amount of phthalocyanine precursors. The high-efficiency ORR performance and scalable synthesis of Cu–N–C and Fe–Cu–N–C catalysts enabled them to be the potential substitutes to Pt-based electrocatalyst for ORR.     

The effect of heteroatoms doping for the Pt supported graphene hollow spheres on electrocatalytic properties towards oxygen reduction and hydrogen evolution reaction

Noble metal Pt is the acknowledged efficient catalyst for oxygen reduction (ORR) and hydrogen evolution reaction (HER) in commercial applications. However, due to its high price and limited reserves, its large-scale application is limited. In order to overcome this defect, the loaded Pt nanoparticles (NPs) should be small and dispersed efficiently through the design of electrode materials, so as to improve the utilization efficiency of Pt. In addition, the introduction of non-noble metal active sites can reduce the consumption of Pt efficiently. In this work, hollow graphene spheres are used as the carrier and the heteroatoms (N, Fe and Co) are introduced. The results show that the introduction of Fe and Co can form very effective heteroatom active sites (carbon encapsulated Fe/Co metals and FeCo alloy, and/or metal nitrides Fe/Co-N_x-C) in the substrate material, which improve the catalytic activity of the electrode material effectively and the utilization efficiency of Pt. In addition, the generation of Fe/Co-N_x-C active sites and the loading of Pt are also closely related to the doped N atoms. The onset potential, limiting current density (J_L), half-wave potential (E_1/2) and Tafel slope of sample FeCo-N_xHGSs/Pt (10 wt%) can exceed or comparable to those of commercial catalysts Pt/C (20 wt%) towards ORR both in acid and alkaline electrolyte. Moreover, the values of η₁₀₀ and the Tafel slope for FeCo-N_xHGSs/Pt towards HER can also exceed the commercial catalysts Pt/C (20 wt%) in acid and alkaline electrolytes. The purpose of reducing the usage amount of precious metals without reducing the catalytic performance is realized. The relationship between the ORR and HER performance of the resultant electrode catalyst and the doped heteroatoms, such as nitrogen (N), iron (Fe) and cobalt (Co) atoms, was studied and discussed in detail.     

Iron-gelatin aerogel derivative as high-performance oxygen reduction reaction electrocatalysts in microbial fuel cells

Currently, precious based materials are known as highly efficient and widely used catalysts for oxygen reduction reaction (ORR). The expensive price and scarce resource of precious metals have stimulated researchers to explore low-cost and high-performance non-precious metal catalysts. Gelatin is a promising precursor to prepare cost-effective and high-performance catalysts because of abundant micropores and nitrogen self-doping sites after pyrolysis. Herein, we developed a new highly active ORR catalyst (G/C–Fe-2) containing Fe–N coordination sites and Fe/Fe₃C nanoparticles. G/C–Fe-2 exhibited excellent ORR electrocatalytic activity (onset potential: 0.21 V, and limiting current density:7.36 mA cm^?2) and high-performance in air-cathode MFCs (Output voltage: 660 mV, and maximum power density: 560 mW m^?2). It is significant for synthesizing low-cost and high-activity ORR electrocatalysts through this strategy.     

Carbon supported Pt-Y electrocatalysts for the oxygen reduction reaction

Carbon supported Pt₃Y (Pt₃Y/C) and PtY (PtY/C) were investigated as oxygen reduction reaction (ORR) catalysts. After synthesis via reduction by NaBH₄, the alloy catalysts exhibited 10-20% higher mass activity (mA mg_Pt⁻¹) than comparably synthesized Pt/C catalyst. The specific activity (μA cm_Pt⁻²) was 23 and 65% higher for the Pt₃Y/C and PtY/C catalysts, respectively, compared to Pt/C. After annealing at 900 °C under a reducing atmosphere, Pt₃Y/C-900 and PtY/C-900 catalysts showed improved ORR activity; the Pt/C and Pt/C-900 (Pt/C catalyst annealed at 900 °C) catalysts exhibited specific activities of 334 and 393 μA cm_Pt⁻², respectively, while those of the Pt₃Y/C-900 and PtY/C-900 catalysts were 492 and 1050 μA cm_Pt⁻², respectively. X-ray diffraction results revealed that both the Pt₃Y/C and PtY/C catalysts have a fcc Pt structure with slight Y doping. After annealing, XRD showed that more Y was incorporated into the Pt structure in the Pt₃Y/C-900 catalyst, while the PtY/C-900 catalyst remained unchanged. Although these results suggested that the high ORR activity of the PtY/C-900 catalyst did not originate from Pt-Y alloy formation, it is clear that the Pt-Y system is a promising ORR catalyst which merits further investigation.     

A novel CuFe-based catalyst for the oxygen reduction reaction in alkaline media

The primary objective of this work is to develop alternative electrocatalysts to Pt-based materials for the oxygen reduction reaction (ORR) in alkaline fuel cells. We synthesized a bicore CuFe/C composite electrocatalyst by impregnation of iron and copper phthalocyanine-based complexes into a carbon support, followed by pyrolysis at 800-900 °C in an Ar atmosphere. This novel composite catalyst exhibits electrochemical performance for ORR in 0.1 M KOH similar to a commercial Pt/C (BASF Fuel Cell, 30%) catalyst at 6-fold lower CuFe loading. High resolution X-ray photoelectron spectroscopy (HR-XPS) results indicate that coordination bonding between Fe and N atoms still remains and show that a mixed Cu(I)/Cu(II) valency exists in the CuFe/C catalyst after high temperature heat treatment. The Cu(I)/Cu(II) redox mediator adjacent to Fe atoms is crucial to provide electrons to the N_xFe-O₂ adduct and maximize the overall rate of the reduction reaction. The results of this study may offer a new approach to development of efficient catalysts for oxygen reduction to water in alkaline media.     

Zr enhanced Fe,N, S co-doped carbon-based catalyst for high-efficiency oxygen reduction reaction

Fe-N_x catalysts have received widespread attention in recent years due to their excellent catalytic performance, hoping to replace platinum for oxygen reduction reactions (ORR). In recent years, more studies have shown that when the catalyst contains two or more metals doped, its catalytic performance will be improved. Herein, using the high temperature pyrolysis method, through the incorporation of the second phase metal (Zr), melamine as the nitrogen source, and thiourea as the sulfur source, a high-activity carbon-based catalyst doped with Fe and Zr bimetals was synthesized. Originating from the strong interaction between Fe species and ZrO₂ clusters and the promotion of O₂ adsorption by ZrO₂ nanoparticles supported on nitrogen-doped carbon, this catalyst has a better ORR electrocatalytic performance than 46% TKK commercial platinum carbon in 0.1 M KOH, exhibiting an onset potential of 1.047 V vs RHE, a half-wave potential of 0.909 V vs RHE. It provides a new idea for the preparation of high-performance bimetallic-doped carbon-based electrocatalysts.     

Reduced graphene oxide supported Fe2B as robust catalysts for oxygen reduction reaction

Transition metal borides have great potential to be low-cost, high-performance catalysts for novel energies despite the synthesis is rather difficult. In this paper, the reduced graphene oxide (rGO) supported iron boride (Fe₂B/rGO) based catalysts are synthesized by a facile reduction method. The successful synthesis of Fe₂B is confirmed by X-ray diffraction, scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), X-ray photo-electron spectroscopy (XPS) and other tests. HRTEM tests showed that the constructed Fe₂B was embedded in the rGO, where B played the role of coordination atoms which could regulate the electronic structure of the catalysts and improve the catalytic performance towards oxygen reduction reaction (ORR). The electrochemistry tests showed that the peak current intensity of the Fe₂B/rGO catalyzed ORR could be reached up to 7.6 mA/cm², which surpassed that of the Pt/C (20 wt%) catalyst. The current intensity can be kept at 82.47% after continuous running 20,000 s, which is higher than the Pt/C catalyst (79.4%). The onset potential reaches up to 0.95 V, which is only 0.06 V lower than that of Pt/C (20 wt%) catalyst. Both RDE and RRDE tests confirmed that the Fe₂B/rGO catalyzed ORR major happed through 4-electron pathway. The redistributed electron between iron and boron atoms promoted the happening of ORR on Fe₂B/rGO catalysts. The results of this work provide a novel way to develop high performance transition metal boride based catalysts for ORR.     

Fe,N codoped porous carbon nanosheets for efficient oxygen reduction reaction in alkaline and acidic media

Electrospinning typically employed to fabricate nanofibers was first used to prepare Fe and N doped porous carbon nanosheets (Fe–N/CNs) as oxygen reduction reaction (ORR) electrocatalysts. Polyacrylonitrile nanofibers containing a small amount of ferrocenes (Fer-PAN) were produced by electrospinning. When Fer-PAN was preoxidized at 300 °C in the air (Fer-PAN-300), nanosheets were formed and occupied the interspace between nanofibers. Fe–N/CNs was finally obtained using carbonized Fer-PAN-300 at 900 °C in N₂. The Fe–N/CNs incorporated the advantages of carbon nanofiber webs and porous nanocarbon materials, inclusive of comparatively high conductivity and large specific surface area. In both alkaline and acidic electrolyte, the Fe–N/CNs took on similar even better ORR catalytic activity than other catalysts reported elsewhere, and better stability than those of commercial Pt/C.     

Boron doping induced electronic reconfiguration of Fe-Nx sites in N-doped carbon matrix for efficient oxygen reduction reaction in both alkaline and acidic media

Developing non-precious metal-based catalysts as the substitution of precious catalysts (Pt/C) in oxygen reduction reaction (ORR) is crucial for energy devices. Herein, a template and organic solvent-free method was adopted to synthesize Fe, B, and N doped nanoflake-like carbon materials (Fe/B/N–C) by pyrolysis of monoclinic ZIF-8 coated with iron precursors and boric acid. Benefiting from introducing B into Fe–N–C, the regulated electron cloud density of Fe-N_x sites enhance the charge transfer and promotes the ORR process. The as-synthesized Fe/B/N–C electrocatalyst shows excellent ORR activity of a half-wave potential (0.90 V vs 0.87 V of Pt/C), together with superior long-term stability (95.5% current density retention after 27 h) in alkaline media and is even comparable to the commercial Pt/C catalyst (with a half-wave potential of 0.74 V vs 0.82 V of Pt/C) in an acidic electrolyte. A Zn-air battery assembled with Fe/B/N–C as ORR catalyst delivers a higher open-circuit potential (1.47 V), specific capacity (759.9 mA h g^?1_Zn at 10 mA cm^?2), peak power density (62 mW cm^?2), as well as excellent durability (5 mA cm^?2 for more than 160 h) compared to those with commercial Pt/C. This work provides an effective strategy to construct B doped Fe–N–C materials as nonprecious ORR catalyst. Theoretical calculations indicate that introduction of B could induce Fe-N_x species electronic configuration and is favorable for activation of OH1 intermediates to promote ORR process.     

Zeolitic-imidazolate-framework-derived Fe-NC catalysts towards efficient oxygen reduction reaction

The development of non-precious metal catalysts to replace scarce and expensive Pt-based catalysts is critical for oxygen reduction reactions (ORR), where zeolitic-imidazolate-framework-derived (ZIF-derived) iron-based electrocatalysts hold a promising prospect. Herein, Fe₃O₄ was used as Fe source, and ZIF-8 was used as C and N source to prepare Fe-NC catalysts. Specifically, the half-wave potential (E_1/2) of the Fe-NC reached 0.90 V, which was higher than commercial Pt/C catalysts (0.87 V), and the overpotential of OER reached 327 mV. In addition, the power density tested in Zn-air batteries upped to 129.59 mW cm⁻², surpassing that of the Pt/C (108.93 mW cm⁻²). The superior performance was attributed to the effective introduction of Fe, the large specific surface area (851.6 m² g⁻¹), relatively regular porous structure and the high degree of graphitization.     

Transition metal carbides coupled with nitrogen-doped carbon as efficient and stable Bi-functional catalysts for oxygen reduction reaction and hydrogen evolution reaction

Developing non-precious metal catalysts for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) is crucial for proton exchange membrane fuel cell (PEMFC), metal-air batteries and water splitting. Here, we report a in-situ simple approach to synthesize ultra-small sized transition metal carbides (TMCs) nanoparticles coupled with nitrogen-doped carbon hybrids (TMCs/NC, including WC/NC, V₈C₇/NC and Mo₂C/NC). The TMCs/NC exhibit excellent ORR and HER performances in acidic electrolyte as bi-functional catalysts. The potential of WC/NC at the current density of 3.0 mA cm^?2 for ORR is 0.814 V (vs. reversible hydrogen electrode (RHE)), which is very close to Pt/C (0.827 V), making it one of the best TMCs based ORR catalysts in acidic electrolyte. Besides, the TMCs/NC exhibit excellent performances toward HER, the Mo₂C/NC only need an overpotential of 80 mV to drive the current density of 10 mA cm^?2, which is very close to Pt/C (37 mV), making it the competitive alternative candidate among the reported non-precious metal HER catalysts.