Boosting photoelectrochemical water splitting of bismuth vanadate photoanode via novel co-catalysts of amorphous manganese oxide with variable valence states

Bismuth vanadate (BVO) is a promising photoanode while suffers from sluggish oxygen evolution kinetics. Herein, an ultra-thin manganese oxide (MnOx) is selected as co-catalyst to modify the surface of BVO photoanode by a facile spray pyrolysis method. The photoelectrochemical measurements demonstrate that surface charge transport efficiency (gsurface) of MnOx modified BVO photoanode (BVO/MnOx) is strikingly increased from 6.7 % to 22.3 % at 1.23 VRHE (reversible hydrogen electrode (VRHE)). Moreover, the gsurface can be further boosted to 51.3 % at 1.23 VRHE after applying Ar plasma on the BVO/MnOx sample, which is around 7 times higher comparing with that of pristine BVO samples. Additional characterizations reveal that the remarkable PEC performance of the Ar-plasma treated BVO/MnOx photoanode (BVO/MnOx/Ar plasma) could be attributed to the increased charge carrier density, extended carrier lifetime and additional exposed Mn3+ active sites on the BVO surface. This investigation could provide a new understanding for the design of BVO photoanode with superior PEC performance based on the modification of MnOx and plasma surface treatment.