Chiral‐Induced Spin Selectivity Steering OH‐to‐OOH Conversion for Efficient Photoelectrochemical Water Splitting

ABSTRACT The spin state of oxygen intermediates constitutes a fundamental limitation to the four‐electron oxygen evolution reaction (OER), impeding efficient photoelectrochemical water splitting. Herein, guided by the chiral‐induced spin selectivity (CISS) effect, we design a chiral L‐Co _(3−x) Ni _x O ₄ /BiVO ₄ photoanode that employs a chiral co‐catalyst layer to accelerate the evolution of oxidative intermediates. Kinetic isotope experiments, in situ attenuated total reflection Fourier Transform infrared spectroscopy and density functional theory calculations demonstrate that aligning the spin states of charge carriers via chiral molecules facilitates the rapid conversion of ^* OH to ^* OOH. Meanwhile, this process effectively suppresses the formation of hydrogen peroxide (Faradaic efficiency < 10%) and improves photoanode stability. Consequently, the L‐Co _(3−x) Ni _x O ₄ /BiVO ₄ photoanode achieves a photocurrent density of 5.41 mA·cm ⁻² at a potential of 1.23 V vs. the reversible hydrogen electrode, and maintains stable operation for over 100 h at the working voltage. This work unravels the underlying mechanism by which the CISS effect governs the OER pathway and mediates the formation of key reaction intermediates and provides a viable spin‐engineering route to efficient and stable photoanodes.