Etching time effect on morphological, optical and photoelectrochemical properties of BiVO4 electrodeposited films

Abstract

The impact of etching time on the surface morphology, crystallinity, light absorption, and the photoelectrochemical characteristics of BiVO4 thin films prepared by electrodeposition method has been studied to remove excess V2O5 on top of BiVO4. BiVO4 films were first electrodeposited on fluorine-doped tin oxide (FTO) electrodes at a deposition time of 30 min, followed by annealing at 500 °C. Excess V2O5 was then removed by chemical etching in an aqueous KOH solution. The samples were characterized by FE-SEM, XRD, EDX, EDX-mapping, UV–Vis, and photoelectrochemical analyses. The morphology, porosity, crystallinity, and light absorption of BiVO4 films and those treated with KOH for 20 min (the optimal etching time, which yielded the highest photocurrent) could be changed by etching time, according to the results. The photocurrent density of the BiVO4 film etched for 20 min was 60 µA/cm2 at +1.0 V vs. Ag/AgCl which was 8.2 times higher than the corresponding value for BiVO4 film prior to etching. The very long duration (30 mins) led to the poor performance of the films prepared since only 22 µA/cm2 at +1.0 V vs. Ag/AgCl of photocurrent was generated. Thus, the etching time must be well optimized to ascertain the complete removal of the excess V2O5 without damaging the BiVO4 film.