Role of Gd in Enhancing the Charge Carrier Mobility of Spray–Deposited BiVO₄ Photoanodes

Abstract

The emergence of BiVO4 as one of the most promising photoanodes for solar water splitting is largely driven by the success in dopant introduction and optimization to improve its photoelectrochemical performance. To this end, although less commonly used, several trivalent ions (e.g., In3+, Gd3+) that substitute Bi3+ have also been demonstrated to be effective dopants, which can increase the photocurrent of BiVO4 photoanodes. However, the main factor behind such improvement is still unclear as various explanations were proposed in the literature. Herein, Gd3+ is introduced to substitute Bi3+ in spray‐deposited BiVO4 films, which enables up to a ∼2‐fold photocurrent increase. Further analysis suggests that Gd‐doping enhances the carrier separation in BiVO4 and does not affect the catalytic and optical properties. Indeed, time‐resolved microwave conductivity measurements reveal that the carrier mobility of BiVO4 is increased by 50% with the introduction of Gd, while the carrier lifetime is unaffected. This mobility increase 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 performance of BiVO4.

Interface Engineering of a 2D/2D BiVO4/Bi4V2O10 Heterostructure with Improved Photocatalytic Photoredox Activity

“…From enlarged view between 700 cm –1 and 950 cm –1 shown in Figure b, we can clearly observe that the characteristic peaks at 829 cm –1 shifted toward higher frequency region as the BiVO 4 loading contents increased, implying a decrease in the V–O bond length. Because of the deformation of VO 4 3– affected by the Bi 3+ lone-pair electron induced in BiVO 4 , the overlapping of Bi 6s and O 2p orbitals at the valence band became greater, which had been reported to be beneficial to the more effective transfer of photoexcited holes toward the surface of BiVO 4 , where they triggered the photocatalytic reaction . The UV-vis diffuse reflectance spectra shown in Figure c were used to determine the optical properties of different samples.…”

“…Because of the deformation of VO 4 3− affected by the Bi 3+ lonepair electron induced in BiVO 4 , the overlapping of Bi 6s and O 2p orbitals at the valence band became greater, which had been reported to be beneficial to the more effective transfer of photoexcited holes toward the surface of BiVO 4 , where they triggered the photocatalytic reaction. 35 The UV-vis diffuse reflectance spectra shown in Figure 3c were used to determine the optical properties of different samples. The absorption edges of the BiVO 4 −Bi 4 V 2 O 10 heterostructures showed a redshift with the increasing of Bi 4 V 2 O 10 content due to visiblelight absorption contributed by Bi 4 V 2 O 10 .…”

Laser-induced deposition of Ni, Co-doped FeOOH cocatalysts on WO3 photoanodes and elucidating their roles in water oxidation in terms of carrier dynamics

“…In a PEC cell, a semiconductor electrode converts light energy into chemical energy that is stored in hydrogen molecules. Among the transition metal oxide n-type semiconductor materials, TiO 2 , 3,4 α-Fe 2 O 3 , 5–9 BiVO 4 , 10,11 and WO 3 (ref. 12 and 13) are the most frequently employed photoanode materials in PEC cells.…”

Improved Charge Separation and Injection Efficiencies of Bismuth Vanadate Photoanode by Depositing Composite CoOx/CuO Cocatalyst

“…[7] What's more, the valence and conduction bands of the materials need to be appropriate for the water oxidation redox and proton reduction potentials. [8] Otherwise, it is necessary to prepare inexpensive and long-term reservation materials. [9] Scientists have been carrying out a great many of studies to satisfy the above requirements for efficient water splitting.…”

“…In order to absorb a large portion of the solar spectrum including visible light, the photoanode of an efficient photoelectrochemical system needs sufficiently small band gap [7] . What's more, the valence and conduction bands of the materials need to be appropriate for the water oxidation redox and proton reduction potentials [8] . Otherwise, it is necessary to prepare inexpensive and long‐term reservation materials [9] .…”