Gradient Mo‐Doped BiVO ₄ Thin Films via Ultrasonic Spray Pyrolysis for Enhanced Photoelectrochemical Water Oxidation

Element doping is one of the important strategies to improve the charge separation and transfer efficiency of BiVO 4 photoanode. In contrast to uniform doping, gradient doping further improves charge separation by establishing a built‐in electric field through spatially graded dopant distribution. The synthesis method for effective element doping needs to be further explored. In this paper, the designable gradient molybdenum (Mo)‐doped BiVO 4 thin films were successfully prepared by a facile programmable ultrasonic spray pyrolysis process. The best performing gradient Mo‐doped BiVO 4 thin film exhibits the of 2.56 mA/cm 2 at 1.23V versus reversible hydrogen electrode, which is 3.2 times higher than the undoped BiVO 4 thin film, due to the improved charge separation efficiency. This performance is comparable to other Mo‐doped BiVO 4 photoanode that employ gradient doping via traditional methodologies reported in the literature. Our work offers an effective strategy for rapid and uniform preparation of gradient element‐doped films by ultrasonic spray pyrolysis system.