Stable Cocatalyst‐Free BiVO₄ Photoanodes with Passivated Surface States for Photocorrosion Inhibition

Abstract

Improving charge transport and reducing bulk/ surface recombination can increase the activity and stability of BiVO 4 for water oxidation. Herein we demonstrate that the photoelectrochemical (PEC) performance of BiVO 4 can be significantly improved by potentiostatic photopolarization. The resulting cocatalyst-free BiVO 4 photoanode exhibited a record-high photocurrent of 4.60 mA cm À2 at 1.23 V RHE with an outstanding onset potential of 0.23 V RHE in borate buffer without a sacrificial agent under AM 1.5G illumination. The most striking characteristic was a strong "self-healing" property of the photoanode, with photostability observed over 100 h under intermittent testing. The synergistic effects of the generated oxygen vacancies and the passivated surface states at the semiconductor-electrolyte interface as a result of potentiostatic photopolarization reduced the substantial carrier recombination and enhanced the water oxidation kinetics, further inhibiting photocorrosion.

Operando Infrared Spectroscopy Reveals the Dynamic Nature of Semiconductor–Electrolyte Interface in Multinary Metal Oxide Photoelectrodes

“…Similarly, several works in the literature investigating the long-term PEC stability of BiVO 4 in similar conditions have observed a gradual increase in the photocurrent over the first few hours (∼20−30 h) of the stability tests, but have failed to unambiguously explain this behavior. 9,49 In the infrared spectroscopy data in this work, when BiVO 4 is illuminated under open-circuit conditions, only vanadium dissolution is observed from the BiVO 4 surface. When an anodic potential is applied in the dark conditions in a phosphate buffer electrolyte, the infrared spectra were completely reversible and no bismuth or vanadium dissolution was observed.…”

“…Gao et al studied photopolarized BiVO 4 under a transmission electron microscope (TEM) and observed the development of a thin evenly distributed amorphous layer at the surface of BiVO 4 , ∼3 nm thick, after prolonged photopolarization. 49 However, the exact composi- tion of this layer was not revealed. XPS data from previous works suggested an increase in the concentration of bismuth at the BiVO 4 surface post-photocharging.…”

“…The cathodic shift in the open-circuit potential during photocharging is thus also an indication of the change in the surface composition of BiVO 4 .The preferential removal of vanadium from the surface upon illumination will result in a bismuth-dominated surface on top of the pristine bulk BiVO 4 . Gao et al studied photopolarized BiVO 4 under a transmission electron microscope (TEM) and observed the development of a thin evenly distributed amorphous layer at the surface of BiVO 4 , ∼3 nm thick, after prolonged photopolarization 49. However, the exact composi-…”

Cu2S/BiVO4 Heterostructure Photoanode with Extended Wavelength Range for Efficient Water Splitting

“…As shown in the XPS spectra of Figure a,c, the peaks at 158.94, 164.24 eV, 516.57, and 523.97 eV are assigned to Bi 4f 7/2 , Bi 4f 5/2 , V 2p 3/2 , and V 2p 1/2 in bare BiVO 4 , respectively . The O 1s spectrum (Figure b) can be deconvoluted into three peaks corresponding to metal oxides (O–metal), oxygen atoms in the region of oxygen vacancy (O V ), and hydrogen–oxygen bond (O–H), respectively. , When Cu 2 S is deposited on BiVO 4 , the binding energy of Bi 4f, V 2p, and O 1s spectra was shifted significantly to high binding energy probably due to the filling of oxygen vacancies with the ratio of O v to O L changed from 4:10 to 1.8:10. , For the region of Bi 4f 7/2 (Figure a), a pair of shoulder peaks located at lower binding energies (158.27 and 163.57 eV) were observed likely owing to the interaction between BiVO 4 and Cu 2 S, resulting in the formation of Bi–S bonds . Additionally, two peaks at 161.27 and 162.47 eV from S 2– are presented in the middle .…”

“…36,37 When Cu 2 S is deposited on BiVO 4 , the binding energy of Bi 4f, V 2p, and O 1s spectra was shifted significantly to high binding energy probably due to the filling of oxygen vacancies with the ratio of O v to O L changed from 4:10 to 1.8:10. 34,38 For the region of Bi 4f 7/2 (Figure 3a), a pair of shoulder peaks located at lower binding energies (158.27 and 163.57 eV) were observed likely owing to the interaction between BiVO 4 and Cu 2 S, resulting in the formation of Bi−S bonds. 39 Additionally, two peaks at 161.27 and 162.47 eV from S 2− are presented in the middle.…”