Enhanced photocatalytic CO2 reduction activity of Z-scheme CdS/BiVO4 nanocomposite with thinner BiVO4 nanosheets

Abstract

Construction of Z-scheme photocatalysts has drawn much attention in the field of CO2 reduction. However, research on photoreduction CO2 for monoclinic bismuth vanadate (m-BiVO4) is restricted due to its low conduction band potential and short electron diffusion lengths. To address the issues, we herein constructed a series of CdS/BiVO4 nanocomposites by depositing CdS on the surface of BiVO4 coupling with controlling the thickness of BiVO4 nanosheets. The morphological, crystalline, band alignment and optical properties of the samples are investigated intensively. Photocatalytic performance is evaluated by measuring the ability of the photocatalysts to convert CO2 into CO and hydrocarbon fuels, primarily CH4. The composites exhibit more efficient photocatalytic activity than CdS and BiVO4, and the yields of CH4 and CO vary depending on the thickness of BiVO4 substrate. The maximum yields of CH4 and CO for CdS/BiVO4 with 55–75 nm BiVO4 are 2.98 and 1.31 μmol g−1 after 5 h irradiation, while those for its counterpart with 15–30 nm BiVO4 attain 8.73 and 1.95 μmol g−1, respectively. The enhanced photoactivity of the composites is attributed to the band structure and Z-scheme charge transfer mode. Besides, thinner BiVO4 nanosheets are confirmed to be favorable for improving the photoreduction CO2 efficiency due to shorter electron diffusion lengths.