Ni3S2-MoSx nanorods grown on Ni foam as high-efficient electrocatalysts for overall water splitting

In order to solve the problem of large overpotential in water electrolysis for hydrogen production, transition metal sulfides are promising bifunctional electrocatalysts for hydrogen evolution reaction/oxygen evolution reaction that can significantly reduce overpotential. In this work, Ni₃S₂ and amorphous MoS_x nanorods directly grown on Ni foam (Ni₃S₂-MoS_x/NF) were prepared via one-step solvothermal process, which were used as a high-efficient electrocatalyst for overall water splitting. The Ni₃S₂-MoS_x/NF composite exhibits very low overpotentials of 65 and 312 mV to reach 10 mA cm⁻² and 50 mA cm⁻² in 1.0 M KOH for HER and OER, respectively. Besides, it exhibits a low Tafel slope (81 mV dec⁻¹ for HER, 103 mV dec⁻¹ for OER), high exchange current density (1.51 mA cm⁻² for HER, 0.26 mA cm⁻² for OER), and remarkable long-term cycle stability. This work provides new perspective for further the development of highly effective non-noble-metal materials in the energy field.     

A nano-spherical structure Ni3S2/Ni(OH)2 electrocatalyst prepared by one-step fast electrodeposition for efficient and durable water splitting

Developing non-noble metal catalysts with excellent electrocatalytic performance and stability is of great significance to hydrogen production by water electrolysis, but there are still problems of low activity, complex preparation and high cost. Herein, we fabricated a novel Ni₃S₂/Ni(OH)₂ dual-functional electrocatalyst by a one-step fast electrodeposition on nickel foam (NF). While maintaining the electrocatalytic performance of Ni₃S₂, the existence of heterostructure and Ni(OH)₂ co-catalyst function greatly improves the overall water splitting performance of Ni₃S₂/Ni(OH)₂–NF. Hence, It shows a low overpotential of 66 mV at 10 mA cm^?2 for HER and 249 mV at 20 mA cm^?2 for OER. The dual-functional electrocatalyst needs only 1.58 V at 20 mA cm^?2 when assembled two-electrode electrolytic cell. Impressively, the electrocatalyst also shows outstanding catalytic stability for about 800 h when 20 and 50 mA cm^?2 constant current was applied, respectively which demonstrates a potential electrocatalyst for overall water splitting.     

Reduced graphene oxide composite Ni3S2 microspheres grown directly on nickel foam as an efficient electrocatalyst for OER

The development of cheap, high-efficiency, and stable oxygen evolution reaction (OER) electrocatalysts is a current research hotspot. In this work, reduced graphene oxide (rGO) composite Ni₃S₂ microspheres grown directly on nickel foam (Ni₃S₂-rGO/NF) were prepared by tube furnace calcination and hydrothermal method. The Ni₃S₂-rGO/NF had excellent OER catalytic activity and stability with an overpotential of 303 mV at the current density of 100 mA cm⁻², which was 100 mV lower than that of Ni₃S₂/NF, and its Tafel slope was as low as 23 mV·dec⁻¹. The main reason for enhancing OER activity of the Ni₃S₂-rGO/NF is due to synergistic effect of Ni₃S₂ microspheres and rGO, which inhibited the production of NiS and refined the micron size of Ni₃S₂. This work offers a new method for developing stable and efficient OER catalysts.     

Facile one-pot synthesis of binder-free nano/micro structured dendritic cobalt activated nickel sulfide: a highly efficient electrocatalyst for oxygen evolution reaction

Reasonable design and preparation of non-noble metal electrocatalysts with predominant catalytic activity and long-term stability for oxygen evolution reaction (OER) are essential for electrocatalytic water splitting. Ni foam (NF) is highlighted for its 3D porous structure, impressive conductivity and large specific surface area. Herein, nano/micro structured dendritic cobalt activated nickel sulfide grown on 3D porous NF (Co–Ni₃S₂/NF) has been successfully synthesized by one-step hydrothermal method. Due to the ingenious incorporation of Co, Co–Ni₃S₂/NF electrode shows auspicious electrocatalytic performance for OER compared with Ni₃S₂/NF electrode. As a result, Co–Ni₃S₂/NF needs overpotential of only 274 and 459 mV at current density of 10 and 50 mA cm⁻², respectively, while Ni₃S₂/NF requires overpotential of 344 and 511 mV. At potential of 2.0 V (vs. RHE), Co–Ni₃S₂/NF displays current density of 191 mA cm⁻², while Ni₃S₂/NF just attains current density of only 135 mA cm⁻². Moreover, Co–Ni₃S₂/NF demonstrates excellent stability for uninterrupted OER in alkaline electrolyte. The strategy of designing and preparing cobalt activated nickel sulfide grown on NF renders a magnificent prospect for the development of metal-sulfide-based oxygen evolution catalysts with excellent electrocatalytic performances.     

One-step preparation of Fe-doped Ni3S2/rGO@NF electrode and its superior OER performances

In order to improve the OER performance, Ni₃S₂-based catalysts were directly grown on Ni substrate by simultaneously doping of Fe and compositing with reduced graphene oxide (rGO). Synthesis and loading of Ni₃S₂/rGO were completed during a one-step hydrothermal process, in which Ni foam acted as support and Ni source of Ni₃S₂, as well as the subsequent current collector. It is found that either GO or Fe salt tuned Ni₃S₂ nanosheets into thinner and smaller interconnected nanosheets anchored on rGO, which enhanced the charge transfer resistance and improved the active sites. Hence, as-synthesized Fe-doped Ni₃S₂/rGO composite at 120 °C (Fe-2-Ni₃S₂/rGO@NF-120) exhibited an enhancement on OER performances: An overpotential of 247 mV at 20 mA cm⁻², and a small Tafel slope of 63 mV dec⁻¹, as well as an excellent stability of: 20 h maintaining at 20 mA cm⁻² or 50 mA cm⁻².     

One-pot preparation of Ni3S2@3-D graphene free-standing electrode by simple Q-CVD method for efficient oxygen evolution reaction

Efficient non-noble metal catalysts for the oxygen evolution reaction (OER) are particularly important in the practical applications of electrocatalytic water splitting (ECWS). Herein, based on a simple quasi chemical vapor deposition (Q-CVD) method, we fabricate a newly Ni₃S₂@3-D graphene free-standing electrode for efficient OER applications. The Ni₃S₂@3-D graphene integrates the advantageous features of 3-D graphene and Ni₃S₂ towards OER, such as more interfacial catalytic sites, pore-rich structure, N-doped structure and good electrical conductivity. Benefiting from the favorable features, the Ni₃S₂@3-D graphene (especially 900 °C sample) exhibits excellent OER performances in alkaline medium, which includes a low on-set potential (1.53 V), low overpotential of 305 mV at a current density of 10 mA cm⁻², and a smaller Tafel slope (50 mV dec⁻¹). This catalyst also shows ultrahigh stability after chronoamperometry response at 10 mA cm⁻² for 48 h with 30% increase in the current density. The present work opens a new approach for the one-pot construction of hybrid materials between metal sulfide and graphene to increase the electrocatalytic activity of non-noble metal OER catalysts.     

Cu2S/Ni3S2 ultrathin nanosheets on Ni foam as a highly efficient electrocatalyst for oxygen evolution reaction

It is an inevitable choice to find efficient and economically-friendly electrocatalysts to reduce the high overpotential of oxygen evolution reaction (OER), which is the key to improve the energy conversion efficiency of water splitting. Herein, we synthesized Cu₂S/Ni₃S₂ catalysts on nickel foam (NF) with different molar ratios of Ni/Cu by a simple two-step hydrothermal method. Cu₂S/Ni₃S₂-0.5@NF (CS/NS-0.5@NF) effectively reduces the overpotential of OER, displaying small overpotentials (237 mV@100 mA cm^?2 and 280 mV@500 mA cm^?2) in an alkaline solution, along with a low Tafel slope of 44 mV dec^?1. CS/NS-0.5@NF also presents an excellent durability at a relatively high current density of 100 mA cm^?2 for 100 h. The excellent performance is benefited by the prominent structural advantages and desirable compositions. The nanosheet has a high electrochemical active surface area and the porous structure is conducive to electrolyte penetration and product release. This work provides an economically-friendly Cu-based sulfide catalyst for effective electrosynthesis of OER.     

Construction of NiCo2S4/Ni3S2 nanoarrays on Ni foam substrate as an enhanced electrode for hydrogen evolution reaction and supercapacitors

Developing a multifunctional and sustainable electrode material for hydrogen evolution reaction and supercapacitors is a highly feasible avenue for producing the high energy density and renewable energies. In our study, nanostructured NiCo₂S₄/Ni₃S₂/NF nanoarrays are rational developed in experiments via a simple hydrothermal reaction. Ascribed to the 3D nanostructured NiCo₂S₄/Ni₃S₂ with numerous exposure active sites and large contact areas for the electrolyte, the binder-free feature of NiCo₂S₄/Ni₃S₂/NF facilitates a low charge transfer resistance, as well as the synergetic effect of NiCo₂S₄ and Ni₃S₂. The obtained electrocatalyst showed ultrahigh electrocatalytic activity with an overpotential of 111 mV at 10 mA cm⁻² and a Tafel slope of 57 mV dec⁻¹. In addition, the electrode showed an area specific capacity of 6.13 F cm⁻² at 10 mA cm⁻² and superior rate capability (2.72 F cm⁻² at 80 mA cm⁻²), accompanied by excellent cycling stability. This results presented in our work can provide an effective strategy for rational design of other hybrid materials with excellent electrochemical performance in the application of electrocatalysis and supercapacitors.     

Electrodeposition of NiS/Ni2P nanoparticles embedded in amorphous Ni(OH)2 nanosheets as an efficient and durable dual-functional electrocatalyst for overall water splitting

To develop earth-abundant and cost-effective catalysts for overall water splitting is still a major challenge. Herein, a unique “raisins-on-bread” Ni–S–P electrocatalyst with NiS and Ni₂P nanoparticles embedded in amorphous Ni(OH)₂ nanosheets is fabricated on Ni foam by a facile and controllable electrodeposition approach. It only requires an overpotential of 120 mV for HER and 219 mV for OER to reach the current density of 10 mA cm⁻² in 1 M KOH solution. Employed as the anode and cathode, it demonstrates extraordinary electrocatalytic overall water splitting activity (cell voltage of only 1.58 V @ 10 mA cm⁻²) and ultra-stability (160 h @ 10 mA cm⁻² or 120 h @50 mA cm⁻²) in alkaline media. The synergetic electronic interactions, enhanced mass and charge transfers at the heterointerfaces facilitate HER and OER processes. Combined with a silicon PV cell, this Ni–S–P bifunctional catalyst also exhibits highly efficient solar-driven water splitting with a solar-to-hydrogen conversion efficiency of 12.5%.     

NiFe2O4–Ni3S2 nanorod array/Ni foam composite catalyst indirectly controlled by Fe3+ immersion for an efficient oxygen evolution reaction

A NiFe alloy was designed on nickel foam (NF) as a precursor using cathodic electrodeposition. NiFe₂O₄–Ni₃S₂ nanorods (NRs) composite catalysts were prepared by Fe³⁺ impregnation and further hydrothermal sulfuration methods. NiFe₂O₄–Ni₃S₂ nanosheets (NSs) were also prepared by direct hydrothermal sulfuration of the NiFe alloy for comparison. Compared to the dense NS structure of the NiFe₂O₄–Ni₃S₂ NSs/NF, the NiFe₂O₄–Ni₃S₂ NRs/NF showed better oxygen evolution performance due to its unique weed-like NR array structure composed of additional oxygen evolution reaction (OER) active sites, with a strong electron interaction for Ni and Fe and the active sulfide synergistic effect with oxides. Therefore, Driving a current density of 10 mA cm^?2 only requires an overpotential of 189 mV and the catalyst could provide 100 mA cm^?2 continuously and be constant for more than 80 h in 1.0 M KOH. This experiment indicated that Fe³⁺ immersion had an indirect regulating effect on the morphological growth of the catalyst, which provided a novel concept for designing better OER catalysts.     

Facile construction of heterostructural Ni3(NO3)2(OH)4/CeO2 bifunctional catalysts for boosted overall water splitting

Interface engineering has aroused vitally widespread concern since it could be an effective strategy for exploring high-performance and low-cost water oxidation electrocatalysts. Herein, we report a hetero-structured Ni₃(NO₃)₂(OH)₄/CeO₂/NF (NNO/CeO₂/NF) electrode, exhibiting superior performance owning to the NO₃^? anion substitution for the OH^? in nickel hydroxide to form Ni₃(NO₃)₂(OH)₄, together with its interface synergy with ceria. In alkaline solution, the NNO/CeO₂/NF electrocatalyst could catalyze the OER with an overpotential of 330 mV to approach 50 mA cm^?2. Also, it needs only an overpotential of 120 mV to reach 10 mA cm^?2 for HER. Additionally, when a standard two-electrode water electrolyzer is fabricated by employing NNO/CeO₂/NF as both the cathode and anode, it can generate 10 mA cm^?2 at 1.64 V and operate steadily without performance degradation after 25 h. This research provides a novel perspective for reasonable design of advanced catalytic materials with improvements in the field of electrocatalysis.     

The 3D ultra-thin Cu1-xNixS/NF nanosheet as a highly efficient and stable electrocatalyst for overall water splitting

In recent years, the exploration of efficient and stable noble-metal-free electrocatalysts is becoming increasingly important, used mainly for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). In this work, a new ultrathin porous Cu_1-xNi_xS/NF nanosheets array was constructed on the 3D nickel skeleton by two-step method: hydrothermal method and vulcanization method. Through these two processes, Cu_1-xNi_xS/NF has a larger specific surface area than that of foamed nickel (NF) and Cu_1-xNi_xO/NF. The Cu_1-xNi_xS/NF materials show excellent catalytic activity by accelerating the electron transfer rate and increase the amount of H₂ and O₂ produced. The lower overpotential was obtained only 350 mV at 20 mA cm⁻² for OER, not only that, but also the same phenomenon is pointed out in HER, optimal Cu_1-xNi_xS/NF presents low overpotentials of 189 mV to reach a current density of 10 mA cm⁻² in 1.0 M KOH for HER. Both OER and HER shows a lower Tafel slope: 51.2 mV dec⁻¹ and 127.2 mV dec⁻¹, subsequently, the overall water splitting activity of Cu_1-xNi_xS/NF was investigated, and the low cell voltage was 1.64 V (current density 10 mA cm⁻²). It can be stable for 14 h during the overall water splitting reaction. These results fully demonstrate that Cu_1-xNi_xS/NF non-precious metal materials can be invoked become one of the effective catalysts for overall water splitting, providing a richer resource for energy storage.     

Ultrathin-layered MoS2 hollow nanospheres decorating Ni3S2 nanowires as high effective self-supporting electrode for hydrogen evolution reaction

High-activity and cost-effective transition metal sulfides (TMSs) have attracted tremendous attention as promising catalysts for hydrogen evolution reaction (HER). However, a significant challenge is the simultaneous construction of abundant electrochemical active sites and the fast electronic transmission path to boost a high-efficient HER. Herein, we demonstrate a facile one-step hydrothermal preparation of MoS₂ hollow nanospheres decorating Ni₃S₂ nanowires supported on Ni foam (NF), without any other additional template, surfactant or annealing. In this three-dimensional (3D) heterostructure, the ultrathin-layered MoS₂ hollow nanospheres contribute to the promotion of the total surface area and the electrochemical active sites. Meanwhile, the Ni₃S₂ nanowires are beneficial to the high electrical conductivity. Consequently, the optimized MoS₂/Ni₃S₂/NF-200-24 electrocatalyst presents an extremely superior HER activity to that of individual MoS₂/NF and Ni₃S₂/NF. The HER overpotentials are 85 mV at 10 mA cm⁻² and 189 mV at 100 mA cm⁻², which are also comparable with the state-of-the-art 20% Pt/C/NF electrode at both low and high current.     

Controlled synthesis of Mn3O4/Co9S8–Ni3S2 on nickel foam as efficient electrocatalyst for oxygen evolution reaction

Advances in electrochemical interfaces have greatly facilitated the development of new energy systems that can replace traditional fossil fuels. Oxygen evolution reaction (OER) is the core reaction in the new energy conversion system to produce hydrogen. Here, nanorods structure of Mn₃O₄/Co₉S₈–Ni₃S₂/NF-4 was designed and assembled. The Mn₃O₄ has served as an appropriate matrix to build a composite structure with Co₉S₈–Ni₃S₂ to enhance the stability of catalyst. And the introduction of Mn regulated the electronic structure of Ni and Co, which increased the OER activity of matericals. Further characterization and electrochemical testing have suggested that between polymetallic can effectively optimize conductivity and enhance reaction kinetics. Mn₃O₄/Co₉S₈–Ni₃S₂/NF-4 can achieve overpotential of 188 mV at the current density of 10 mA cm^?2 in alkaline solution, with small Tafel slope of 43.2 mV dec^?1 and satisfactory stability of 30 h at 10 mA cm^?2. This work may show a feasible reference in the design of high-efficient OER catalysts.     

Superhydrophilic 3D peony flower-like Mo-doped Ni2S3@NiFe LDH heterostructure electrocatalyst for accelerating water splitting

Constructing highly efficient nonprecious electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is essential to improve the efficiency of overall water splitting, but still remains lots of obstacles. Herein, a novel 3D peony flower-like electrocatalyst was synthesized by employing Mo–Ni₂S₃/NF nanorod arrays as scaffolds to in situ growth ultrathin NiFe LDH nanosheets (Mo-Ni₂S₃@NiFe LDH). As expected, the novel peony flower-like Mo–Ni₂S₃@NiFe LDH displays superior electrocatalytic activity and stability for both OER and HER in alkaline media. Low overpotentials of only 228 mV and 109 mV are required to achieve the current densities of 50 mA cm^?2 and 10 mA cm^?2 for OER and HER, respectively. Additionally, the material remarkably accelerates water splitting with a low voltage of 1.54 V at 10 mA cm^?2, which outperforms most transition metal electrodes. The outstanding electrocatalytic activity benefits from the following these features: 3D peony flower-like structure with rough surface provides more accessible active sites; superhydrophilic surfaces lead to the tight affinity between electrode with electrolyte; metallic Ni substrate and highly conductive Mo–Ni₂S₃ nanorods scaffold together with offer fast electron transfer; the nanorod arrays and porous Ni foam accelerate gas bubble release and ions transmission; the strong interfacial effect between Mo-doped Ni₃S₂ and NiFe LDH shortens transport pathway, which are benefit for electrocatalytic performance enhancement. This work paves a new avenue for construction and fabrication the 3D porous structure to boost the intrinsic catalytic activities for energy conversion and storage applications.     

Engineering bimetallic cactus-like NiFeOOH/CoNiSe2 heterostructure nanosheets for efficient oxygen evolution and overall water splitting

The development of structural stable, high-performance, inexpensive electrocatalysts for oxygen evolution reactions (OER) is essential to alleviate the energy crisis. Herein, cactus-like CoNiSe₂ was synthesized on nickel foam and NiFeOOH was electrodeposited on surface of CoNiSe₂ to form a core-shell structural electrode. The obtained NiFeOOH/CoNiSe₂/NF exhibited ultra-low overpotentials of 204 mV and 234 mV at 10 and 100 mA cm⁻², with a Tafel slope of 26.2 mV dec⁻¹ in 1 M KOH alkaline solution. Furthermore, the current density only decreased by 5% after a 100 h durability test at 200 mA cm⁻², showing excellent robust stability. A two-electrode system with NiFeOOH/CoNiSe₂/NF as anode and Ni/NiO@MoO_3-x/NF as cathode (NiFeOOH/CoNiSe₂/NF||Ni/NiO@MoO_3-x/NF) showed a low voltage of 1.47/1.56 V to deliver 10/100 mA cm⁻². According to the experimental and density functional theory (DFT) results, the strong electronic interactions at the NiFeOOH/CoNiSe₂/NF interface leads to an increase in the valence state of Fe and an optimisation of the adsorption free energy, which are favourable to reduce the energy consumption of the OER. This work obtained high performance OER electrocatalysts by engineering amorphous and crystalline heterointerfaces and structural design, which will provide some inspiration for similar work.     

Autologous growth of Fe-doped Ni(OH)2 nanosheets with low overpotential for oxygen evolution reaction

Highly active and durable electrocatalysts for oxygen evolution reaction (OER) play a vital role in water splitting. Despite numerous efforts, the strategies to prepare durable and effective electrocatalysts via scalable methods still remain a great challenge. In this work, we fabricated Fe-doped Ni(OH)₂ ultrathin nanosheets (Fe–Ni–OH/Ni) via autologous growing of Ni(OH)₂ from Ni foam, and in situ electrochemical-assisted doping Fe into Ni(OH)₂. Benefiting from the unique structure with large surface areas and strong coupling effects between Fe and Ni, the optimal Fe–Ni–OH electrodes exhibit remarkable catalytic performance toward OER, which requires an overpotential of 220 mV to achieve a current density of 10 mA cm⁻² with a Tafel slope of 48.3 mV dec⁻¹. The Fe–Ni–OH electrodes also possess high stability even under a high current density of 500 mA cm⁻² for 600 h with an ultralow overpotential of 290 mV. Using Ni–Fe–OH electrodes as both anode and cathode for overall water splitting, only a small overpotential of 1.57 V is required to reach a current density of 10 mA cm⁻². Moreover, the high catalytic performance and scalable preparation method can meet the emergency needs for the practical application.     

MoS2/NiFeS2 heterostructure as a highly efficient electrocatalyst for overall water splitting at high current densities

Searching for efficient, stable and low-cost nonprecious catalysts for oxygen and hydrogen evolution reactions (OER and HER) is highly desired in overall water splitting (OWS). Herein, presented is a nickel foam (NF)-supported MoS₂/NiFeS₂ heterostructure, as an efficient electrocatalyst for OER, HER and OWS. The MoS₂/NiFeS₂/NF catalyst achieves a 500 mA cm⁻² current density at a small overpotential of 303 mV for OER, and 228 mV for HER. Assembled as an electrolyzer for OWS, such a MoS₂/NiFeS₂/NF heterostructure catalyst shows a quite low cell voltage (≈1.79 V) at 500 mA cm⁻², which is among the best values of current non-noble metal electrocatalysts. Even at the extremely large current density of 1000 mA cm⁻², the MoS₂/NiFeS₂/NF catalyst presents low overpotentials of 314 and 253 mV for OER and HER, respectively. Furthermore, MoS₂/NiFeS₂/NF shows a ceaseless durability over 25 h with almost no change in the cell voltage. The superior catalytic activity and stability at large current densities (>500 mA cm⁻²) far exceed the benchmark RuO₂ and Pt/C catalysts. This work sheds a new light on the development of highly active and stable nonprecious electrocatalysts for industrial water electrolysis.     

3D V–Ni3S2@CoFe-LDH core-shell electrocatalysts for efficient water oxidation

Studying cheap and efficient electrocatalysts is of great significance to promote the sluggish kinetics of oxygen evolution reaction (OER). Here, we adopted a simple two-step method to successfully prepare the 3D V–Ni₃S₂@CoFe-LDH core-shell electrocatalyst. The V–Ni₃S₂@CoFe-LDH/NF shows excellent OER performance with low overpotential (190 mV at 10 mA/cm² and 240 mV at 50 mA/cm²), small Tafel slope (26.8 mV/dec) and good long-term durability. Excitingly, to reach the same current density, V–Ni₃S₂@CoFe-LDH/NF electrode even needs much smaller overpotential than RuO₂. Furthermore, the outstanding OER activity of V–Ni₃S₂@CoFe-LDH/NF is ascribed to the following reasons: (1) V–Ni₃S₂ nanorod cores improve the conductivity and ensure the fast charge transfer; (2) CoFe-LDH nanosheets interconnected with each other provide more exposed active sites; (3) the unique 3D core-shell structures are favorable for electrolyte diffusion and gas releasing. Our work indicates that building 3D core-shell heterostructure will be a useful way to design good electrocatalysts.     

Porous flower-like nickel nitride as highly efficient bifunctional electrocatalysts for less energy-intensive hydrogen evolution and urea oxidation

Finding a suitable replacement for the high potential of anodic water electrolysis (oxygen evolution reaction (OER)) is significant for hydrogen energy storage and conversion. In this work, a simple and scalable method synthesizes a structurally unique Ni₃N nanoarray on Ni foam, Ni₃N-350/NF, that provides efficient electrocatalysis for the urea oxidation reaction (UOR) that transports 10 mA cm⁻² at a low potential of 1.34 V. In addition, Ni₃N-350/NF exhibits electro-defense electrocatalytic performance for hydrogen evolution reaction, which provides a low overpotential of 128 mV at 10 mA cm⁻². As proof of concept, all-water-urea electrolysis measurement is carried out in 1 M KOH with 0.5 M Urea with Ni₃N-350/NF as cathode and anode respectively. Ni₃N-350/NF||Ni₃N-350/NF electrode can provide 100 mA cm⁻² at a voltage of only 1.51 V, 160 mV less than that of water electrolysis, which proves its commercial viability in energy-saving hydrogen production.