Hierarchically porous nickel foam supported Fe-Ni₃S₂ electrode for high-current-density alkaline water splitting

Alkaline water electrolysis (AWE) offers a promising route for green hydrogen production. However, its industrial application is impeded by unsatisfactory energy conversion efficiency. Herein, a robust electrode composed of porous nickel foam (PNF) and Fe-doped Ni₃S₂ (Fe-Ni₃S₂) nanosheet arrays was fabricated and applied for industrial AWE. By conducting a scalable dynamic bubble-template method, PNF with high loading of active catalysts was prepared. The superhydrophilicity of PNF facilitates bubble detachment and promotes mass transfer, especially at high current densities. In addition, Fe-Ni₃S₂ with optimized electronic structure is featured with enhanced electrical conductivity, sufficient exposure of active sites, and optimized adsorption of intermediates. Benefiting from the concerted advantages of PNF and Fe-Ni₃S₂, the obtained Fe-Ni₃S₂/PNF-5 electrode with an optimal Fe content of 5 mol% exhibits high catalytic activity for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Compared with the Pt/C/NF||IrO₂/NF couple, the Fe-Ni₃S₂/PNF-5||Fe-Ni₃S₂/PNF-5 couple delivers a current density of 10 mA cm^-2 at a low cell voltage of 1.50 V for AWE. Under industrial conditions, a competitive cell voltage of 1.75 V is needed for achieving a high current density of 400 mA cm^-2. Besides, the couple can operate stably for 120 h, outperforming the commercial RN||RN couple. This work provides a novel strategy to elevate the loading amount of catalysts and improve the electrochemical performance of the electrode for practical AWE application.