Facile Spray Deposition of Photocatalytic ZnO/Cu–In‐Zn‐S Heterostructured Composite Thin Film

We present a sprayed composite thin film, comprising Cu−In‐Zn−S (CIZS) particles embedded in ZnO matrix for photoelectrochemical hydrogen production from water splitting. CIZS, a photoactive semiconductor was used as a photon absorber, whereas ZnO channels as the pathway for charge transfer. It was found that the distribution of the CIZS particles had a direct impact on the photoelectrochemical (PEC) activity. A more homogeneous dispersion of smaller CIZS particles (0.56 μm) within ZnO matrix exhibited a higher photocurrent density, and 3.27 μmol/ cm2 hydrogen evolution for 5 h. Electrochemical impedance spectroscopy (EIS) was employed to analyze the charge transfer mechanism of this composite thin film. In addition, ZnO coating on top of CIZS particles also served as the adhesion and protection layers. All the PEC experiments were performed in 0.5 M K2SO4 electrolyte. No sacrificial reagents were used. The composite electrode was stable under illumination: 75.67 % of photo‐activity remained after 1 h illumination at a bias of 0.2 V vs. SCE. This study demonstrates a simple and low‐cost spray preparation of composite thin film consisting of particles embedded in any semiconductor matrix. In the PEC experiments, no sacrificial reagents were used. The sample C3 with more homogeneous dispersion of smaller CIZS particles within ZnO matrix exhibited a higher photocurrent. 3.27 μmol/cm2 of produced hydrogen was collected in 5 hours. This work provided a simple and low‐cost way to prepare a heterostructured composite photoelectrode.