Engineering a Triphasic Co(OH)F/Co–S/CeO 2 Nanostructure Interface for Promoting Hydrazine-Assisted Overall Water Splitting

Synthesizing bifunctional electrocatalysts capable of concurrently accelerating the kinetics of both hydrogen evolution reaction (HER) and hydrazine oxidation reaction (HzOR) remains a formidable hurdle with academic research. Herein, a nanoneedle-like electrocatalyst with a triphasic nanointerface, consisting of crystalline Co(OH)F, amorphous Co–S, and crystalline CeO 2, was synthesized on nickel foam (NF) (Co(OH)F/Co–S/CeO 2 /NF) through an integrated hydrothermal–sulfidation–deposition strategy. Co(OH)F/Co–S/CeO 2 /NF not only possessed abundant active sites but also minimized charge-transfer resistance and optimized electron distribution across interfaces, thus significantly accelerating reaction kinetics. Then, it demonstrated an overpotential of 153 mV for the HER and a low potential of 80 mV for the HzOR at 10 mA cm –2, respectively. Employing Co(OH)F/Co–S/CeO 2 /NF as a bifunctional catalytic electrode, an impressively low cell voltage of 0.20 V was sufficient to achieve a flow of 10 mA cm –2 during hydrazine-assisted overall water splitting. Density functional theory calculations elucidated that the superior performance of Co(OH)F/Co–S/CeO 2 /NF for both HER and HzOR was originated from the balanced hydrogen adsorption energy (Δ G H* ) during the HER process and the altered rate-limiting step with a relatively low energy barrier in HzOR. This research offers valuable insights into the development of sophisticated bifunctional electrocatalysts, significantly advancing large-scale deployment of energy-conserving H 2 production technologies.