Electrospun Mo-BiVO4 for Efficient Photoelectrochemical Water Oxidation: Direct Evidence of Improved Hole Diffusion Length and Charge separation

Abstract

Bismuth vanadate (BiVO4) is a promising visible light absorbing material for use as a photoanode in photoelectrochemical water splitting. The present study reports fabrication of nanoporous Molybdenum (Mo) doped BiVO4photoanodes by a simple and scalable electrospinning technique. Water oxidation photocurrent increases by up to four times, and a ten-fold increase in incident photon-to-current conversion efficiency (IPCE) was achieved by Mo doping. Significant enhancement in the photocurrent under front side illumination conditions compared to back side illumination was observed for the Mo-doped samples. Estimation of the hole diffusion lengths of pristine and Mo-doped BiVO4using the Gartner modelshowed an increase in hole diffusion lengths from 47nm to 183nm after Mo doping. This was supported further by open circuit photovoltage decay measurements where the better charge separation was revealed for Mo:BiVO4.Overall, the enhanced photoelectrochemical water oxidation with Mo doping can be attributed to increased charge separation and enhanced hole diffusion length, which reduced charge transfer resistance for water oxidation.