Self-Flux Method in Sputtered BiVO4 Films for Enhanced Photoelectrochemical Performance

Bismuth vanadate (BiVO4) is a well-sought candidate as a photoanode in photoelectrochemical (PEC) water splitting. The mismatch between the V/Bi ratio affects the photocatalytic efficiency of BiVO4 films fabricated using the large-area sputtering method. We adopt a facile method to finely control the V/Bi ratio in sputtered films by changing the oxygen partial pressure. We observed the formation of various phases, with a change of V/Bi ratio in the films ranging from 0.5 to 2, and found that the segregated V2O5 acts as a self-flux in improving the crystallinity of BiVO4, resulting in a long carrier lifetime. With the prolonged carrier lifetime from 0.098 to 0.211 ns, the optimized films realize a photocurrent density of 1.97 mA/cm(2) at 1.23 V versus reversible hydrogen electrode. However, V2O5 itself does not exhibit a lifetime comparable to BiVO4, which implies that an excess amount of V2O5 is detrimental to PEC performance. These findings point to the significance of a slightly V-rich growth environment for advancing the PEC performance of BiVO(4 )materials. Our work provides insights into the growth of high-quality crystals by controlling composition in other multielement oxides.