Elucidating the enhanced photoelectrochemical performance of zinc-blende ZnS/wurtzite ZnO heterojunction and adsorption of water molecules by molecular dynamics simulations

Abstract

ZnS-containing industrial waste (hereafter referred to as ZnS-IW) from the mining/metallurgy industry is modified with hydrothermally synthesized ZnO for study the enhancement of UV-light-induced photocurrent. The XRD, SEM and TEM results reveal that submicron-sized rod-like crystals of ZnO are deposited on large plate-like particles of ZnS-IW. Significant improvement in UV-induced photocurrent is reported for the 1:1 ratio photoanode (ZnS-IW:ZnO), ∼24 and ∼8 times compared to pristine ZnS-IW and ZnO, respectively, this measured at the potential that maximizes power density: 0.5 V vs. Ag–AgCl. The photocurrent response correlates well with the Gärtner-Butler theory and the formation of a ZnS-IW@ZnO heterojunction was supported by the positions of the valence and conduction bands, lifetime measurements and specific adsorption of water molecules. In fact, molecular modeling calculations indicate that the incorporation of ZnO leads to higher adsorption of water with the preferential formation of a monolayer, proving the synergetic effect due the heterojunction. The optoelectronic properties of these functional materials make them good candidates to support photocatalysis and light-sensing applications.