Elongation of ZnWO4 nanocrystals for enhanced photocatalysis and the effects of Ag decoration

Abstract

Glycine was originally studied as a morphology modifier for the hydrothermal crystallization of ZnWO4 nanocrystals, which led to high aspect ratio nanorods and short tetragonal prisms at the glycine/Zn2+ molar ratios (R) of 0.5 and 3, respectively. It was discussed that glycine affects the nucleation and [0 0 1] growth of ZnWO4 crystallites via chelation and selective adsorption. Photocatalytic evaluation via bleaching methyl orange (MO) solution under UV irradiation found that the efficiency of degradation increases with increasing aspect ratio of the ZnWO4 nanocrystals, and the best catalytic R = 0.5 sample degraded ~99.5% of the MO molecules within ~80 min. Surface decoration with Ag nanocrystallites (~5–15 nm) significantly enhanced the efficiency of the least reactive R = 3 sample, but is detrimental to the already highly active R = 0.5 ZnWO4 nanorods. The kinetics of photocatalysis were discussed from the morphology/structure of the catalysts by considering the involved photoreactions.