Tuning *OH Oxidativity via a Cu-Co(OH)₂ Cocatalyst on a Hematite Photoanode for Selective Cyclohexanone Oxidation

Photoelectrochemical (PEC) synthesis provides a sustainable route to produce adipic acid (AA) from cyclohexanone. However, the sluggish kinetics inherent to this complex multielectron-transfer process severely constrain the reaction efficiency. This paper describes a strategy to tune the oxidativity of surface-adsorbed hydroxyl species (*OH) for selective AA synthesis, implemented by integrating a Cu-doped cobalt hydroxide (Cu-Co(OH)₂) cocatalyst onto a hematite-based photoanode. The as-prepared photoanode achieved an AA productivity of 10.4 μmol cm^-2 h^-1 with a Faradaic efficiency of 88.7% at 1.2 V vs RHE. Mechanistic study reveals that the incorporated Cu acts as an electronic modulator, inducing electron-deficient characteristics at the active Co sites. This electronic modulation effect enhances the electrophilicity of *OH, thereby boosting its intrinsic oxidative capacity. This study demonstrates a feasible pathway to tailor the oxidative capacity of active species via electronic modulation of the cocatalyst, providing new insights into the design of advanced PEC systems for the synthesis of value-added chemicals.