Influence of Mo doping on interfacial charge carrier dynamics in photoelectrochemical water oxidation on BiVO 4

• Published in: Sustainable energy & fuels 2023-06, Vol.7 (12), p.2923-2933
• Main Authors: Wu, Xiaofeng, Oropeza, Freddy E., Qi, Zheng, Einert, Marcus, Tian, Chuanmu, Maheu, Clément, Lv, Kangle, Hofmann, Jan P.
• Format: Article
• Language: English
• ISSN: 2398-4902; 2398-4902
• DOI: 10.1039/D3SE00061C

The understanding of interfacial charge transfer processes is vital to the design of efficient photoanodes in photoelectrochemical (PEC) water splitting. Bismuth vanadate (BiVO 4 ) is a promising photoanode material to drive the oxygen evolution reaction (OER). However, intrinsic BiVO 4 suffers from a slow charge carrier mobility and sluggish OER kinetics, which gives rise to a high charge carrier recombination rate and unsatisfactory photoelectrochemical performance. Although the impact of metal doping of BiVO 4 in the field of photocatalysis and photoelectrochemistry has been investigated in literature, a detailed understanding of the interfacial charge carrier dynamics in dependence of surface configuration is still required for further PEC device optimization. In this work, BiVO 4 film samples were prepared by a modified metal organic precursor decomposition method. Effects of molybdenum (Mo) doping on the photocurrent density, electrochemical impedance spectra and interfacial charge transfer kinetics of BiVO 4 were investigated. Our results indicate: (1) interfacial charge transfer resistances ( R ct ) of BiVO 4 in 0.1 M phosphate buffer solution decrease 2 to 3 orders of magnitude under illumination. (2) Intensity of the photocurrent is predominantly limited by R ct , rather than the semiconductor bulk resistance ( R bulk ). (3) Mo doping does not only increase photovoltage, but also obviously decreases R ct . (4) Compared to pristine BiVO 4 , Mo doping leads to an enhancement of photocurrent density at 1.23 V vs. RHE to 25.3 μA cm −2 , i.e. , by a factor 2.7.