Freestanding and Robust Bifunctional Electrode: CoFe-LDH/Co ₃ O ₄ Nanohybrids on Ni Foam for Overall Water Splitting

To mitigate energy crises and environmental pollution, it is of paramount importance to develop a rational approach for creating affordable, stable, efficient, and environmentally friendly bifunctional electrocatalysts based on nonprecious metals for total water splitting. In this study, a series of CoFe-LDH/Co₃O₄/NF-<i>x</i> (<i>x</i> = 0.25, 0.50, 0.75) electrocatalyst materials have been synthesized on nickel foam (NF) by employing a three-step method. The combination of Co₃O₄/NF nanopinelike arrays with stable mechanical strength and CoFe-LDH nanosheets forms channels conducive to rapid electron transfer, thereby enhancing the catalytic activity of the materials. Of the materials synthesized, the CoFe-LDH/Co₃O₄/NF-0.50 exhibited the most remarkable hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities as an electrocatalyst. The CoFe-LDH/Co₃O₄/NF-0.50||CoFe-LDH/Co₃O₄/NF-0.50 alkaline electrolyzer, employed for overall water splitting, exhibits a cell voltage as low as 1.581 V at a current density of 10 mA cm^-2, along with excellent stability over prolonged cycling. Density functional theory (DFT) calculations reveal synergistic interactions at the CoFe-LDH/Co₃O₄/NF interface and provide insights into the mechanistic processes of the HER/OER catalytic sites. This study provides a foundation for advancing catalyst supports similar to NF in the field of overall water electrolysis.