Effect of photodeposition conditions on Ni–CdS photocatalysts and its role in the photoactivity for H2 production from ethanolic solutions

Abstract

The incorporation of Ni-based cocatalysts on CdS by photodeposition has been investigated as a way of improving the photocatalytic efficiency of CdS for the production of hydrogen from ethanolic solutions under solar light. Specifically, this work investigates the effect of the concentration of CdS in the suspensions used in the photodeposition of Ni over the structure, chemical state, and dispersion of the Ni species deposited on CdS. The change in the concentration of CdS during photodeposition leads to changes in the light absorption capacity of CdS by insertion of Ni2+ ions in its structure, and also in the concentration of heterojunctions formed by the close interaction between the Ni species (Ni(OH)2) and CdS. The Ni–CdS photocatalyst prepared with the lower CdS concentration in the suspension during the photodeposition of Ni showed the highest photoactivity for the production of hydrogen from ethanolic solutions. This outcome is related to the combination of an improvement in the light absorption ability, i.e. narrow band gap associated with a higher insertion of Ni2+ ions in the structure, and an increase in the heterojunctions of Ni(OH)2 on CdS which improves the photo carrier generation, separation and availability on the photocatalyst surface, thus resulting in a more efficient photoproduction of hydrogen.