Mo or W doping into the surface of BiVO4 film photoanodes through a photoelectrochemical treating approach for efficient solar water oxidation

In theory, suitable metal ions doping into the surface of BiVO 4 photoanodes could improve its water oxidation performance effectively. But the common homogeneous reaction strategy is not well applicable for the preparation of BiVO 4 film photoanodes with metal ions surface doping. Herein, a photoelectrochemical treating approach was reported to prepare BiVO 4 films with W or Mo surface doping in saturated tungstate and molybdate-containing electrolyte, respectively. The doping of W or Mo into the surface of BiVO 4 film was attributed to the following reactions. Firstly, the photocorrosion of BiVO 4 film photoelectrodes resulted in the dissolution of VO 4 3+ from BiVO 4 lattice under AM 1.5 G illumination. Then, the WO 4 2+ or MoO 4 2+ in the saturated electrolyte entered and occupied the dissolved sites of VO 4 3+ on BiVO 4 surface through ions exchange reaction . Due to the lower radiative recombination of carrier as well as higher electrocatalytic water oxidation activity, the resultant W or Mo doped BiVO 4 films as photoanodes showed better solar water oxidation activity, kinetics and stability, although their light harvesting property and morphological feature were close to the pristine BiVO 4 film photoanode. The present work provides a new and effective approach for the achievement of metal ions doping into the surface of BiVO 4 photoanodes, which could inspire the preparation of similar photoanode materials.