Enhancing the photocatalytic activity of Cd–ZnS(EN)0.5 hybrid sheets for the H2 production

Abstract

Ultrathin sheets of ZnS(EN)0.5 modified with Cd2+ ions were prepared by chemical precipitation in a mixture of butanol-ethylenediamine-water solution. The Cd2+ content was varied from 0.1 to 0.6 M ratio and its influence in the physicochemical properties of the formed Cd–ZnS(EN)0.5 hybrid compounds was investigated by diverse techniques: X-ray Diffraction, Thermogravimetric, Textural analysis, Infrared, Diffuse Reflectance and X-ray Photoelectron Spectroscopies, Scanning Electron and High-Resolution Transmission Electron Microscopy. The photocatalytic H2 production of the unmodified ZnS(EN)0.5 hybrid was tested using hydrazine, ethanol, and methanol as sacrificial electron donors reagents (SEDr), presenting an H2 evolution rate of 2.4, 21 and 23 μmolh−1, respectively. The results showed that the orthorhombic ZnS(EN)0.5 structure was stable but suffer exfoliation of the lamellar structure during the photocatalytic cycles in methanol-water solution under UV irradiation. The doped Cd–ZnS(EN)0.5 hybrid presented an enhanced H2 production rate (32 μmolh−1) for low Cd2+ doping, showing only minor exfoliation of the lamellar structure and stability of the orthorhombic structure, preserving the high photoactivity after 6 cycles of irradiation.