Pre-catalyst reconstruction in electrochemical processes has recently attracted intensive attention with mechanistic potentials to uncover really active species and catalytic mechanisms and advance targeted catalyst designs. Here, nickel-molybdenum oxysulfide is deliberately fabricated as pre-catalyst to present a comprehensive study on reconstruction dynamics for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkali water electrolysis. Operando Raman spectroscopy together with X-ray photoelectron spectroscopy and electron microscopy capture dynamic reconstruction including geometric, component and phase evolutions, revealing a chameleon-like reconstruction self-adaptive to OER and HER demands under oxidative and reductive conditions, respectively. The in situ generated active NiOOH and Ni species with ultrafine and porous textures exhibit superior OER and HER performance, respectively, and an electrolyzer with such two reconstructed electrodes demonstrates steady overall water splitting with an extraordinary 80% electricity-to-hydrogen (ETH) energy conversion efficiency. This work highlights dynamic reconstruction adaptability to electrochemical conditions and develops an automatic avenue toward the targeted design of advanced catalysts.
Keywords: alkali water electrolysis; chameleon-like reconstruction dynamics; hydrogen evolution reaction; oxygen evolution reaction; really active species.
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