Ultrasound-Triggered Surface Reconstruction with Improved Carriers Transfer Kinetics in CdIn₂S₄ for Solar Water Oxidation

The surface oxygen evolution reaction (OER) is severely restricted owing to the sluggish OER kinetics and limited number of reactive sites. Although surface reconstruction can introduce defects to improve the OER performance, they often function as recombination centers and cause severe carrier recombination. With the aid of ultrasonication, the CdIn2S4 photoanode surface is reconstructed using Zn-modified Cd defects without extreme chemical reaction environment. Owing to the surface reconstruction, the formed type-II band structure is beneficial for separating photogenerated carriers and reduced the bulk recombination. Additionally, the Zn-modified Cd defects are introduced in situ during the ultrasound cavitation process, which facilitated the carrier transfer, reduced the surface recombination, and increased the number of surface active sites. First-principles calculations indicate that the modified Cd defects effectively lower the electrochemical reaction barrier and promote the surface OER kinetics by precisely regulating the four-electron reaction. Consequently, the optimized photoanode exhibits a enhanced photocurrent of 5.30 mA cm⁻² at 1.23 V versus reversible hydrogen electrode. These results demonstrate that an accurate surface reconstruction design can be achieved for introducing and modifying metal defects to improve the transfer and transport behaviors of photogenerated carriers.