Highly nanotextured beta-Bi2O3 pillars by electrostatic spray deposition as photoanodes for solar water splitting

We demonstrate fabrication of films of highly textured bismuth oxide (Bi2O3) pillars via electrostatic spray deposition and test the performance of these films as photoanodes in photoelectrochemical water splitting. The beta-Bi2O3 and alpha-Bi2O3 phases were identified and distinguished using X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. The beta-Bi2O3 pillars of optimized thickness exhibited a photocurrent density of 0.97 mA.cm(-2) at 0.5 V vs Ag/AgCl. The tetragonal beta-Bi2O3 pillars had enhanced visible light absorbance compared to alpha-Bi2O3 as well as other metal oxides like ZnO and TiO2. Tauc plot analysis of film absorbance showed a decrease in the bandgap of the beta-Bi2O3 phase to 2.5 eV. In Na2SO3 electrolyte, a hole scavenger, the onset voltage for the beta-Bi2O3 phase was shifted to a more negative value (-0.4 V), which increased photocurrent density. The electron concentration reached its highest value of 9.1 x 10(20) cm(-3) for the film with the highest photocurrent density. (C) 2018 Elsevier B.V. All rights reserved.