Sriwichai, S.; Irani, R.; Xi, F.; Friedrich, D.; Höhn, C.; Ahmet, I.Y.; Wetchakun, N.; Abdi, F.F.: Role of Gd in Enhancing the Charge Carrier Mobility of Spray-Deposited BiVO4 Photoanodes. Solar RRL 5 (2021), p. 2100268/1-8
10.1002/solr.202100268
Open Access Version
Abstract:
The emergence of bismuth vanadate (BiVO4) as one of the most promising photoanodes for solar water splitting is largely driven by the successful efforts of dopant introduction and optimization to improve its photoelectrochemical (PEC) performance. To this end, although less commonly used, several trivalent ions (e.g., Sm3+, In3+, Gd3+) that substitute Bi3+ have also been demonstrated to be effective dopants, which can increase the photocurrent density of BiVO4 photoanodes. However, the main factor behind such improvement is still unclear, as various explanations have been proposed in the literature. Herein, Gd3+ is introduced to substitute Bi3+ in spray-deposited BiVO4 films, which enables up to a ~2-fold increase in the photocurrent density. Further PEC analysis suggests that Gd-doping enhances the charge carrier separation in the BiVO4 films and does not affect the catalytic and optical properties. Indeed, time-resolved microwave conductivity (TRMC) measurements reveal that the charge carrier mobility of BiVO4 is increased by 50 % with the introduction of Gd while the charge carrier lifetime is unaffected. This increase of mobility is rationalized to be a result of a higher degree of monoclinic lattice distortion in Gd-doped BiVO4, as evident from the X-ray diffraction and Raman spectroscopy data. Overall, these findings provide important insights into the nature and the underlying role of Gd in improving the photoelectrochemical performance of BiVO4 photoanodes.