Ag sputtering-assisted phase formation of Ag2S-decorated ZnS composite sheets and their photoactive performances

Abstract

The Ag2S crystallites-decorated ZnS composite sheets were synthesized by combinational methodology. Two types of ZnS sheet templates were obtained through the vulcanization of ZnO sheets with sulfur precursors of thiourea and Na2S, and then ZnS-Ag2S heterogeneous sheets were obtained with sputtering Ag crystallites and post-annealing procedures. The ZnS sheets have rugged and smooth surfaces formed with sulfur precursors of thiourea and Na2S, respectively. Both the initial microstructures of ZnS sheet templates and Ag2S decoration content affect the photoactivity of the ZnS-Ag2S composite sheets. Compared with the pristine ZnS, the ZnS-Ag2S composite sheets with a suitable Ag2S loading content (Ag at% = 3.6-3.8) are beneficial to improve the photoactivity, which could be explained by the combination of narrow bandgap; Ag2S crystallites would enhance photon absorption and separation efficiency of photoinduced charge carriers. The scavenger tests and photodegradation mechanism show that hydroxyl radicals and holes were the main active species for the ZnS-Ag2S composite sheets to photodegrade methyl orange solution. The experimental results herein provide a novel synthesis approach to decorate Ag2S crystallites onto ZnS with tunable contents and present important design guidelines for the resultant ZnS-Ag2S composite sheets to demonstrate marked improvement in photoactivity.