Tungsten-leaching-induced dynamic self-reconstruction of Fe-modified amorphous mesoporous NiWO4 for efficient water oxidation

Amorphous earth-abundance transition-metal (TM)-based materials are favorable pre-catalysts for the anodic oxygen evolution reaction (OER) in green hydrogen production, owing to their flexible electronic structure, which facilitates reconstruction into electroactive compounds arising from short-range atomic order. Herein, a self-reconstruction driven by in situ electrochemical activation of Fe-modified amorphous mesoporous NiWO 4 to form the electrochemically active Fe-doped NiOOH phase for the efficient OER is reported. Notably, Fe-substitution elevates the O 2p band level closer to the Fermi level, as evidenced by ultraviolet photoelectron spectroscopy (UPS), thereby enabling higher catalytic activity and outstanding alkaline stability of the pre-catalyst (Fe-NiWO 4 ). Various ex situ characterization techniques and density functional theory (DFT) calculations reveal that, under harsh electrochemical activation, the pre-catalyst undergoes W dissolution, generating an oxygen-detective Fe-doped Ni(OH) 2 /NiOOH oxyhydroxide active species. Accordingly, the optimized Fe 0.15 -Ni 0.85 WO 4 (Fe-NiWO 4 ) electrode displays an excellent OER catalytic performance with remarkable values of overpotential (220 mV at 10 mA cm −2 vs RHE), TOF (4.44 s −1 at 300 mV), and Tafel slope (55 mV dec −1 ). This work thus offers an effective model for the design and understanding of the amorphous pre-catalyst for efficient OER.