Constructing dual-site synergy in NiFeOOH via Ce doping and Cr vacancies for robust water oxidation under fluctuating power

Water splitting powered by intermittent renewable energy calls for efficient anode electrocatalysts to overcome both sluggish four-electron OER kinetics and poor durability under fluctuating conditions. Here, we synergistically engineer NiFeOOH with Ce doping and Cr vacancies through a facile one-step electrodeposition method. XPS, XAS and DFT results reveal that Ce doping elevates the Ni valence state to strengthen *OH adsorption, while Cr vacancies redistribute charge around Fe sites to weaken *OH binding. This complementary modulation reduces the Gibbs free energy of the rate-determining step for the OER and promotes the reaction pathway via dual-site synergistic catalysis. It achieves an ultralow overpotential of 280 ± 6.1 mV at 1 A cm −2 with a small Tafel slope of 33.5 mV dec −1 . Notably, the anode exhibits excellent stability under both steady-state (2000 h) and fluctuating (9000 cycles) operation, owing to the rapid charge buffering of the Ce 3+ /Ce 4+ redox couple and the flexible coordination environment arising from Cr vacancy-induced lattice relaxation. Their synergistic effect stabilizes Ni/Fe valence states and M–O bonds, thereby lowering charge consumption, enhancing Faradaic efficiencies and suppressing over-oxidation and deactivation. This study offers an effective route to design resilient anodes for efficient water oxidation under fluctuating power. The 600 cm 2 NiFeOOH catalyst co‑modified with Ce doping and Cr vacancies by electrodeposition, uses Ce 3+ /Ce 4+ redox and Cr vacancies to buffer charge and structure, synergistically stabilizing active sites and optimizing the OER pathway under fluctuating power. Download: Download high-res image (185KB) Download: Download full-size image