Ultrasound Induces Local Disorder of FeOOH on CdIn₂S₄ Photoanode for High Efficiency Photoelectrochemical Water Oxidation

Abstract The regulation of the crystal structure of oxygen evolution cocatalyst (OEC) is a promising strategy for enhancing the photoelectrochemical efficiency of photoanodes. However, the prevailing regulating approach typically requires a multistep procedure, presenting a significant challenge for maintaining the structural integrity and performance of the photoanode. Herein, FeOOH with a local disordered structure is directly grown on a CdIn₂S₄ (CIS) photoanode via a simple and mild sonochemical approach. By modulating the localized supersaturation of Ni ions, ultrasonic cavitation induces Ni ions to participate in the nucleation and growth of FeOOH clusters to cause local disorder of FeOOH. Consequently, the local disordered FeOOH facilitates the exposure of additional active sites, boosting OER kinetics and extending charge carrier lifetimes. Finally, the optimal photoanode reaches 4.52 mA cm⁻² at 1.23 V_RHE, and the onset potential shifts negatively by 330 mV, exhibiting excellent performance compared with that of other metal sulfide‐based photoelectrodes reported thus far. This work provides a mild and controllable sonochemical method for regulating the phase structure of OECs to construct high‐performance photoanodes.