Synthesis, characterization and photocatalytic evaluation of MWO4 (MÂ =Â Ni, Co, Cu and Mn) tungstates

Tungstates have been very scarcely studied as photocatalysts for the production of hydrogen from the dissociation of the water molecule. The aim of the present study is the synthesis and characterization of family tungstate MWO4 (M = Co, Cu, Mn and Ni) materials to evaluate their photocatalytic activity towards the production of hydrogen within the visible light range. CuWO4, CoWO4, NiWO4, and MnWO4 were characterized by XRD, BET, UV-Vis and SEM. Band gap energies of these tungstates fell within the visible light spectrum from 2.24 eV for CoWO4 to 2.56 eV for MnWO4, respectively. Maximum hydrogen production was achieved by MnWO4 with 139 μmolH2/gcat, while the lowest production was observed for sample CoWO4 with 24 μmolH2/gcat. From these results it can be inferred that metal transition tungstates can be considered as potential photocatalysts for H2 production via the splitting of the water molecule under visible light irradiation.