Electronically Modulated FeNi Composite by CeO₂ Porous Nanosheets for Water Splitting at Large Current Density

Exploiting highly active and non-noble metal bifunctional catalysts at large current density is significant for the advancement of water electrolysis. In this work, CeO₂ electronically structure modulated FeNi bimetallic composite porous nanosheets in-situ grown on nickel foam (NiFe₂O₄-Fe₂₄N₁₀-CeO₂/NF) is synthesized. Electrochemical experiments show that the NiFe₂O₄-Fe₂₄N₁₀-CeO₂/NF exhibited the outstanding activities toward both oxygen and hydrogen evolution reactions (OER and HER) (η₁₀₀₀ = 352 mV and η₁₀₀₀ = 429 mV, respectively). When assembled into a two-electrode system for overall water splitting (OWS), it only needs a low cell voltage of 1.81 V to drive 100 mA·cm⁻². And it can operate stably at ±500 mA·cm⁻² over 30 h toward OER, HER and OWS without significant activity changes. The reason could be assigned to the electronic modulating of CeO₂ on FeNi composite, which can boost the intrinsic activity and optimize the adsorption of reaction intermediates. Moreover, the porous nanosheets in-situ grown on NF could enhance the contact of active site with electrolyte and facilitate the gas release, thus improving its chemical and mechanical stabilities. This study highlights a novel approach to design bifunctional non-noble metal catalysts for water splitting at large current density.