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

• Published in: ACS applied energy materials Vol. 5; no. 4; pp. 4191 - 4201
• Main Authors: Liu, Jiaqi, Uezono, Namiki, Tajima, Kazuya, Pawar, Sachin A, Islam, Muhammad Monirul, Ikeda, Shigeru, Sakurai, Takeaki
• Format: Journal Article
• Language: English; Japanese
• Published: American Chemical Society 25.04.2022
• Subjects: films; carrier lifetime; photoelectrochemistry; oxygen partial pressure; composition; BiVO4; flux; sputtering
• ISSN: 2574-0962; 2574-0962
• DOI: 10.1021/acsaem.1c03626

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/cm2 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 BiVO4 materials. Our work provides insights into the growth of high-quality crystals by controlling composition in other multielement oxides.