Role of g-C3N4 in Fabrication of BiVO4/WO3 Z-scheme Heterojunction for high Photoelectrochemical Performances with Enhanced Light Harvesting

Green technology such as harvesting solar light is a promising source for future energy supplies without generating any harmful environmental pollutions. We report a straightforward approach for improving the light harvesting properties of BiVO4 photoanodes in order to enhance their photoelectrochemical performance. A facile sol-gel spin coating method was used to prepare the samples. The g-C3N4 powder was incorporated into the BiVO4 precursor solution before being spin-coated onto fluorine-doped tin oxide glass. After annealing, a thin film of g-C3N4 modified BiVO4 (CN-BiVO4) was formed. A WO3 film was coated onto CN-BiVO4 (CN-BiVO4/WO3) to form a Z-scheme heterojunction and enhance the photoelectrochemical performance. The CN-BiVO4 and CN-BiVO4/WO3 photoanodes outperformed unmodified photoanodes in terms of light harvesting and photoelectrochemical performance. The CN-BiVO4/WO3 had the highest light absorbance and photocurrent density (538 mu A.cm(- 2) at 1.23 V-RHE) and significantly enhanced resilience and stability (with a 35% decay for 1600 s) compared with unmodified electrodes. At 390 nm, the incident photon-to-current conversion efficiency was 14.8%, and the applied bias photon-to-current conversion efficiency was approximately 0.12% at 0.88 V-RHE. These findings reveal that the non-crystalline phases of CN-BiVO4 grains help absorb and trap a broader range of wavelengths, thus improving photoelectrochemical performance.