Screening and characterization for the optimization of CdS-based photocatalysts
Abstract
Scanning electrochemical microscopy (SECM) with an optical fiber was used to rapidly screen M–CdS (M = Cu, Fe, Zn, Co, Ni, Mn and In) photocatalyst arrays for efficient photoelectrochemical reaction. Among the discussed arrays, the spot with the precursor composition In0.2–Cd0.8S showed the highest photocurrent in 0.1 M Na2SO4/Na2SO3 solution under both UV-visible and visible light irradiation. The SECM screening results were also confirmed with bulk photoelectrode studies. The In0.2–Cd0.8S photocatalyst had the hexagonal phase of the wurtzite solid solution structure with an average crystallite size in the range of 13–37 nm. A red shift was observed in the UV-visible absorption spectrum of CdS upon the addition of In. The Mott–Schottky plots showed that the In0.2–Cd0.8S photoelectrode exhibited a flat band potential of −1.2 V vs. Ag/AgCl. The IPCE value at 450 nm radiation for the In0.2–Cd0.8S photocatalyst is 60%, which is three times higher than that of CdS. The superior photocatalytic activity of the In0.2–Cd0.8S photoelectrode is mainly attributed to its high crystallinity, which promotes separation of the photo-induced electrons and holes and also reduces the probability of recombination.