Photocatalytic CO2 reduction activity of Z-scheme CdS/CdWO4 catalysts constructed by surface charge directed selective deposition of CdS

Rational construction of Z-scheme photocatalysts and deep exploration of Z-scheme transfer mechanism are highly desirable for improving the activity of CO2 reduction photocatalysts but remains a significant challenge. Herein, we synthesized a series of heterostructured CdS/CdWO4 materials by selectively depositing CdS nanoparticles on the edges of CdWO4 nanoplates. Selective deposition mechanism of CdS and the formation of the composites were studied in detail. The photocatalytic CO2 reduction activities of the synthesized materials were investigated and the results show that CdS/CdWO4 materials exhibit higher photocatalytic activity than pure CdS and CdWO4. We suggest that the enhanced photoreduction CO2 activity is attributed to Z-scheme charge transfer mechanism based on the analyses of the products of CO2 reduction and the band structure of CdS and CdWO4. Kelvin probe force microscope on CdWO4 nanoplates shows that the photogenerated electrons, driven by electric field forces, would migrate to the edge of CdWO4. The charge transfer direction, coupling with the selective deposition of CdS nanoparticles, facilitates CdS/CdWO4 composites following Z-scheme transfer. In-situ Pt photodeposition tests provide strong experimental support to the charge transfer mechanism. The results gained herein are expected to provide some useful insights into the structure-oriented rational design of Z-scheme photocatalysts for CO2 reduction.