Searching for an efficient electrocatalyst is a massive challenge for hydrogen production in large-scale applications of water decomposition until now. The reported CeO2–FeS catalyst required small overpotentials of 271 and 155 mV at 10 mA cm–2 for OER and HER, respectively. The interfacial Lewis acid–base pair (LABP; Ce···S) in CeO2–FeS improved the activity. The remarkable synergistic effect of CeO2 with FeS increased the active surface area to expose abundant active sites, porosity, and skin-tight contact between CeO2–FeS and NF to regulate the electronic redistribution of Fe sites for remarkable activity. Benefiting from sulfur and oxygen vacancies in CeO2–FeS, the electronic structure of the electrocatalyst can be effectively regulated, and the intrinsic activity of the active site can be enhanced. Notably, benefiting from the sulfur and oxygen vacancies in CeO2–FeS, the electronic structure of the electrocatalyst can be effectively regulated and the intrinsic activity of the active site can be enhanced. Thus, sulfur vacancy and oxygen vacancy are outstanding active sites for HER and OER. The kinetics of CeO2–FeS electrolysis was examined via in situ EIS, demanding very small activation energy to complete the reaction after Ce-coupling, as supported by the Arrhenius plot. The higher rate constant extracted from the Trumpet curve inferred rapid formation of the O2 bubbles. Mechanistic examinations inferred that the built-in electric field (BIEF) at the Schottky interface narrowed the band gap of CeO2–FeS for fast carrier transport and tuned the adsorption ability of intermediates on surface reaction sites. The enhanced *OH adsorption on CeO2–FeS was further verified by Laviron analysis. The alkaline-/solar-driven electrolyzer of CeO2–FeS(+,−) required 1.60 V to get 10 mA cm–2, indicating promising prospects for industrial applications. The Ce4f valence electronic configuration in CeO2–FeS endowed Fe sites with distinguished directive toward HER and OER via Ce4f–Fe3d orbital coupling. The CeO2–FeS interface resulted in balanced adsorption–desorption strength of HER intermediates and optimized the OER reaction pathway by weakening the adsorption capacity of the OOH intermediate. These electronic modulations collectively contribute to the superior catalytic performance.
Kumar et al. (Sun,) studied this question.