WO3 cocatalyst improves hydrogen evolution capacity of ZnCdS under visible light irradiation

Abstract

Semiconductor photocatalysts can convert solar energy into clean pollution-free hydrogen energy and thus are a novel technology to alleviate the energy crisis. To acquire catalysts with higher photocatalytic hydrogen production efficiency, we synthesized ZnCdS catalysts from a hydrothermal method and the WO3 cocatalyst through temperature-programmed reduction. The surface morphology and optical properties of the catalysts were characterized via X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and UV–Vis spectroscopy, which proved the successful synthesis of the WO3/ZnCdS compound catalysts. The effects of WO3 dosage on the photocatalytic activity of ZnCdS were studied, and in particular, the hydrogen production activity of the 35 wt% WO3/ZnCdS was the highest to 98.68 μmol/mg, about 9.6 times that of pure ZnCdS (10.28 μmol/mg). After 5 cycles, it yet had high repeatability and preserved high hydrogen production activity after 100 h of photocatalytic tests. The underlying mechanism was explored via photoluminescence and photocurrent assays. It was found the 35 wt% WO3/ZnCdS generated higher photocurrent than pure ZnCdS, indicating WO3 could facilitate electron transfer to involve more electrons in hydrolysis reactions, thereby increasing the photoelectron use efficiency and photocatalytic hydrogen production activity.