Enhancing Photocurrent of Bismuth Manganate Photoanodes with Nanoislands of Bismuth Oxide

Photoelectrochemical (PEC) water splitting is a promising method for the energy transition. However, it is still hampered because the performance of the electrodes is too low. Herein, bismuth manganate (BMO) is investigated as a photoanode absorber material for PEC. BMO thin films are prepared by a sol–gel method with and without a bismuth oxide (BO) overlayer. It is found that the BO overlayer forms BO nanoislands after annealing. Under visible light illumination, BMO with BO nanoislands results in a nearly tenfold increase of the current density compared to pristine BMO at the same applied potential. This increased performance is related to a decrease in the charge transfer resistance and in the amount of recombinations based on the formation of a favorable heterojunction between BMO and BO. The application of overlayers on electrode materials in combination with suitable band alignment is an effective strategy to improve the performance of PEC electrodes.