Synthesis of WO3/BiVO4 photoanode using a reaction of bismuth nitrate with peroxovanadate on WO3 film for efficient photoelectrocatalytic water splitting and organic pollutant degradation

In this work, we developed a novel, facile, cost-effective method based on a reaction of bismuth nitrate with peroxovanadate on WO3 nanoplate films to synthesize nanostructured WO3/BiVO4 photoanodes, which prevented the introduction of structural defects in the WO3 substrates that occurs in conventional deposition-annealing (DA) methods, for highly efficient photoelectrocatalytic (PEC) water splitting and degradation of organic pollutants. The method is also versatile, allowing dopants such as Mo to be easily incorporated into BiVO4 structures to improve the charge-transfer properties. Both the amount of BiVO4 and doping level can be tailored by modifying the preparation conditions. The PEC performance of the optimized WO3/BiVO4 photoanode was markedly improved with a photocurrent density of 2.83 mA cm−2, which was 9.43 times that of a BiVO4 photoanode and 2.19 times that of a WO3 photoanode. A Mo-doped WO3/BiVO4 (WO3/Mo-BiVO4) photoanode exhibited a further enhanced photocurrent density of 3.78 mA cm−2. Specifically, a cobalt–phosphate (Co–Pi) co-catalyst decorated WO3/Mo-BiVO4 photoanode showed the highest photocurrent density of 5.38 mA cm−2, which is comparable to the values of reported WO3/BiVO4 photoanodes, with stoichiometric H2 (94.7 μmol cm−2 h−1) and O2 (46.5 μmol cm−2 h−1) evolution. Furthermore, the WO3/Mo-BiVO4 photoanode exhibited efficient performance for PEC degradation of organic pollutants with rate constants of 0.683, 0.385, and 1.05 h−1 for tetracycline hydrochloride, phenol, and Congo red, respectively. Intensity-modulated photocurrent spectroscopy measurements indicated the WO3/BiVO4 photoanode should contain fewer nanostructural defects than the WO3/BiVO4 photoanode prepared using DA methods, possibly because the moderate preparation process avoids the harmful repeated heating-cooling process used in DA.