Sulfate-Functionalized Core–Shell ZnO/CdS/Ag₂S Nanorod Arrays with Dual-Charge-Transfer Channels for Enhanced Photoelectrochemical Performance

Insufficient light absorption and fast charge recombination seriously restrain the photoelectrochemical (PEC) water splitting performance of semiconductor photoelectrodes. Herein, sulfate ([SO4])-functionalized CdS was decorated on ZnO nanorod arrays by one-step magnetron sputtering to construct a core–shell heterojunction, and then Ag2S nanoparticles were deposited by cation exchange. The in situ formed [SO4] as an active site is helpful to accelerate charge transfer and enhance PEC reaction kinetics. Additionally, Ag2S was modified on ZnO/CdS to suppress the photocorrosion of CdS while constructing two heterojunctions with a gradient energy band configuration for separating and transporting photogenerated charge carriers efficiently. Benefiting from the dual-charge-transfer channels in [SO4] and Ag2S co-modified ZnO/CdS nanorod arrays, the optimized photoanode presents high PEC performance, yielding a maximum photocurrent density of ∼6.82 mA cm–2 at 1.23 V vs reversible hydrogen electrode (RHE) under simulated air mass (AM) 1.5 solar light illumination, which is 7.75 times that of pristine ZnO photoanode. This work provides a synergetic in situ [SO4] modification and heterojunction construction strategy to design photoelectrodes with multicharge-transfer channels for enhanced PEC performance.