Self-supported bifunctional porous Ni–Fe-based electrode via one-step reduction method for efficient water splitting

Abstract

Efficient, inexpensive, and robust bifunctional electrodes are crucial for water splitting. Herein, the three-dimensional hierarchical porous nickel-iron (Ni–Fe)- based monolith is directly fabricated through a one-step reduction approach of their oxide precursors under a hydrogen atmosphere. The Ni–Fe alloy as the active material of water splitting is simultaneously formed during the reduction process and water is the only by-product, which is facile and environmentally friendly. The effects of the reduction temperatures and the Fe contents on the microstructures and composition of the obtained Ni–Fe samples are systematically investigated. The optimized Ni–Fe-based monolith is used as a self-supporting electrode for oxygen evolution reaction, its electro-oxidized derivatives show a low overpotential of 217 mV at 10 mA cm−2 and an ultralow Tafel slope of 31 mV dec−1 in 1 M KOH. Furthermore, the electrolyzer consisting of the bifunctional electrode demonstrates outstanding performance of 1.49 V at 10 mA cm−2 and exceptional long-term stability over 1000 h at 50 mA cm−2, surpassing the majority of alkaline electrolyzers utilizing Ni–Fe-based electrodes.