The effect of annealing on the photocatalytic activity of ZnxCd1-xS arrays and characterization for the optimization of the photocatalysts

ZnxCd1-xS photocatalyst arrays are prepared using a piezoelectric dispensing system with zinc nitrate, cadmium acetate and thiourea as precursors, a water-glycerol mixture as the reaction solvent and fluorine-doped tin oxide glass as a support. The arrays are annealed in Ar ambient at annealing temperatures that range from 100 to 500 degrees C. The photocatalytic performance of these arrays is evaluated using scanning electrochemical microscopy (SECM) with a scanning optical fiber that is connected to a Xenon lamp, under visible light and UV-visible light irradiation. The spot for the nominal CdS that is annealed at 200 degrees C exhibits the highest photocurrent. The screening results are confirmed by bulk film studies. XPS measurements show that a significant amount of CdO exists in the nominal CdS films that are annealed at a temperature less than 200 degrees C. An increase in the annealing temperature significantly improves the crystalline nature and decreases the amount of CdO. The increase photocatalytic activity of the nominal CdS photoelectrode that is annealed at a temperature of 200 degrees C may be due to the effective separation of photo-generated electron hole pairs and highly active reaction sites because of the formation of the heterostructured (CdS)(0.74)-(CdO)(0.26) composites and the small grain size of photocatalysts. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.