Z‐Scheme Heterojunction of Hierarchical Cu 2 S/CdIn 2 S 4 Hollow Cubes to Boost Photoelectrochemical Performance

Abstract The exaltation of light‐harvesting efficiency and the inhibition of fast charge recombination are pivotal to the improvement of photoelectrochemical (PEC) performance. Herein, a direct Z‐scheme heterojunction is designed of Cu 2 S/CdIn 2 S 4 by in situ growth of CdIn 2 S 4 nanosheets on the surface of hollow CuS cubes and then annealing at 400 °C. The constructed Z‐scheme heterojunction is demonstrated with electron paramagnetic resonance and redox couple ( p ‐nitrophenol/ p ‐aminophenol) measurements. Under illumination, it shows the photocurrent 6 times larger than that of hollow Cu 2 S cubes, and affords outstanding PEC performance over the known Cu 2 S and CdIn 2 S 4 ‐based photocatalysts. X‐ray photoelectron spectroscopy and density functional theory results demonstrate a strong internal electric field formed in Cu 2 S/CdIn 2 S 4 Z‐scheme heterojunction, which accelerates the Z‐scheme charge migration, thereby promoting electron–hole separation and enhancing their utilization efficiency. Moreover, the hollow structure of Cu 2 S is conducive to shortening the charge transport distance and improving light‐harvesting capability. In proof‐of‐concept PEC application, a PEC detection method for miRNA‐141 based on the sensitivity of benzo‐4‐chloro‐hexadienone to light absorption on Cu 2 S/CdIn 2 S 4 modified electrode is developed with good selectivity and a limit of detection of 32 aM. This work provides a simple approach for designing photoactive materials with highly efficient PEC performance.