Investigation on Al³⁺ and Al₂O₃ Coexist in BiVO₄ for Efficient Methylene Blue Degradation: Insight into Surface States and Charge Separation

Abstract

A series of Al-doped BiVO4 composites have been synthesized via the hydrothermal method for methylene blue (MB) degradation application. The reasons for the improvement of photocatalytic performance was explained from the perspective of optics. Transient photovoltage (TPV) measurements suggested that the surface states have the priority to capture photogenerated carriers, and the Al2O3 surface passivation layer can prolong the lifetime of charge carrier. The results of surface photovoltage (SPV), transient photovoltage (TPV), and surface photocurrent (SPC) measurements suggested that the coexistence of Al3+ and Al2O3 caused by the appropriate doping would improve the transfer property and prolong the lifetime of photogenerated carriers. Finally, the possible photocatalytic mechanism is expounded to illustrate the photogenerated charge behavior under visible light irradiation. This work provides a better understanding of the synergistic effect of Al-doping and Al2O3 passivation layer on enhancing the photocatalytic performance.

N-Doped TiO2 Coupled with Manganese-Substituted Phosphomolybdic Acid Composites As Efficient Photocatalysis-Fenton Catalysts for the Degradation of Rhodamine B

“…SPV measurements were performed on the catalysts to investigate the separation and transfer properties of photogenerated carriers on the catalyst surface. Theoretically, a positive signal represents the migration of holes to the surface and negative signal represents electrons transfer to the surface. − Typically, TiO 2 is a n-type semiconductor that should reflect a positive response in the SPV spectra, with which our measurement results were consistent. However, it was shown in Figure a that N-doped TiO 2 exhibited a significant negative signal, indicating a large number of electrons migrating from the bulk phase to the surface.…”

Highly Selective Ammonia Oxidation on BiVO4 Photoanodes Co‐catalyzed by Trace Amounts of Copper Ions

“…Shown in Figure 3d, the cases of both H 2 O and NH 3 exhibited a quick negative sign with a short time scale of 1 μs under laser excitation, which implied that some photogenerated electrons would be immediately captured by the surface defects upon excitation. Subsequently, photogenerated holes were transported toward the surface by both the self‐built field and the concentration gradient [17a] . These negative signals thus transformed into positive responses over a longer period (10 to 1000 μs).…”

“…Generally, a negative TPV response would be generated when negative charges were accumulated nearby the surfaces, and vice versa [17] . The fabrication process of BiVO 4 photoanodes inevitably introduced surface defects, some of which could serve as electron trapping states to capture photogenerated electrons nearby the surfaces [17a] . Shown in Figure 3d, the cases of both H 2 O and NH 3 exhibited a quick negative sign with a short time scale of 1 μs under laser excitation, which implied that some photogenerated electrons would be immediately captured by the surface defects upon excitation.…”

Dynamic semiconductor-electrolyte interface for sustainable solar water splitting over 600 hours under neutral conditions

“…To address these issues, doping strategy, e.g., using Mo (26-28) or W (29)(30)(31)(32) to substitute for V, has been devoted to enhancing the electronic conductivity of BiVO 4 to overcome the transport limitation caused by the short diffusion length (~70 nm) of photogenerated charge carriers. Besides, oxygen evolution catalysts (OECs) decoration [e.g., FeOOH/NiOOH (33)(34)(35)(36) and NiFe oxyhydroxides (37,38)] and surface passivation layers [e.g., TiO 2 (39,40) and Al 2 O 3 (41)] have been shown to alleviate the surface-related limitation of BiVO 4 and improve the catalytic efficiency for OER. For instance, an impressive photocurrent density of 6.73 mA cm −2 at 1.23 V RHE in the KBi electrolyte ( pH 9.5) that approached the theoretical value has been reported using phosphorus-oxygen bonded FeNi catalysts (42).…”