Enhanced photocatalytic hydrogen and methane evolution using chalcogenide with metal ion modification via a microwave-assisted solvothermal method

Abstract

Abstract Copper doped ZnS and Ru, Cu co-doped ZnS nanospheres were successfully synthesized in DI water and ethanol solvent by a microwave-assisted solvothermal method using citric acid surfactants in aqueous medium. Since surfactants could tune the CB edge position to become more negative than hydrogen production level (E =–0.43 eV, H2/H+), 2% Cu-doped ZnS with CIT achieved a higher activity (2961.1 μmol h–1 g–1) for hydrogen evolution compared with pristine ZnS. Cu-doped into the lattice or interstitial of ZnS provides suitable impurity energy levels, which make it easier for the excited electrons from the valence band of ZnS to inject into the conduction band of ZnS. For copper doped ZnS, hydrogen evolution from an aqueous solution containing 0.1 M Na2S at pH 3 and 0.15 g L−1 of 4% Cu-doped ZnS photocatalyst had the maximum of 3717.8 μmol h–1 g–1. Although ruthenium co-doped CuZnS photocatalysts cannot enhance the photocatalytic hydrogen evolution, ruthenium plays an important role as an efficient methanation catalyst. Therefore, the selectivity of 0.5Ru4CuZnS photocatalyst has been shifted towards the co-production of hydrogen and methane.