Enhanced photocatalytic reaction activity of Cu2WS4/Ag2S composite photocatalyst

Coupling noble metal cocatalysts are considered to be one of the most effective approaches to improve photocatalytic performance, but their expensive price limits their practical application. Herein, a series of Cu2WS4/Ag2S nanocomposite photocatalysts were successfully synthesized by a simple ion exchange method using Ag2S as the cocatalyst. Compared with pure Cu2WS4 and Ag2S, the optimized 25 wt% Cu2WS4/Ag2S (CA25) nanocomposites exhibited excellent photocatalytic degradation capability of RhB (96 %,20 min). More importantly, the as-prepared CA25 sample showed a significant photocatalytic hydrogen yield (19.8 μmol/h), which is 9.4 times that of pure Cu2WS4. Systematic studies revealed that the introduction of Ag2S can not only broaden the light absorbance capacity of the composite photocatalyst, but also effectively improve the separation efficiency of the photogenerated carriers. In addition, our results showed that photogenerated electrons simultaneously reduce Ag2S into metallic Ag in the photocatalytic reaction process, that is, metallic Ag can act as the bridge to capture electrons and accelerate the transmission of photogenerated carriers, thus enabling further enhancement of photocatalytic performance. This work provides a new insight for the design of highly efficient composite photocatalysts, and highlights the important role of photocarrier separation in the photocatalytic process.