Particle Size Dependence of Carrier Dynamics and Reactivity of Photocatalyst BiVO₄ Probed with Single-Particle Transient Absorption Microscopy

Abstract

Heterogeneous photocatalytic water splitting under the irradiation of sunlight is an attractive method for generating hydrogen from water. While the photocatalytic mechanism has been extensively studied, most of the experimental studies have been performed with an ensemble of photocatalyst particles with various sizes, morphologies, and secondary structures. To gain a deeper understanding of the mechanism of photocatalysis, it is indispensable to clarify how the geometric structure of photocatalyst affects the kinetics of photogenerated carriers and redox reactions. In this study, the hole decay characteristics and photocatalytic activity of BiVO4, a promising photocatalyst for oxygen evolution with visible light, have been investigated with single-particle transient absorption microscopy. Upon irradiation with 527 nm light, well-faceted nonaggregated crystallites show fast hole decay and little reactivity for Fe3+ reduction. In contrast, aggregated particles with grain boundaries between small primary crystallites show slower hole decay and higher reactivity for Fe3+ reduction than the nonaggregated crystallites. This behavior is increasingly pronounced as the secondary particle size of aggregated crystallite increases. This indicates that grain boundaries in aggregated particles do not work as recombination centers but play an important role in elongation of carrier lifetime and thus in enhancing the reactivity of photocatalyst through trap–detrap processes.

Selectivity Control of the Photo-Catalytic Water Oxidation on SrTiO3 Nanocubes via Surface Dimensionality

“…Particle size effects in photocatalysis have been addressed on various materials including TiO 2 , Cu 2 O, Si, or BiVO 4. The presented results are, however, contradictory. In the case of reduction on Si quantum dots, the resulting activity reportedly increases with decreasing particle size due to a blue shift of the conduction band edge to higher energies .…”

“…11 Water oxidation on size-resolved BiVO 4 gives, on the other hand, an opposite trend due to an increase of hole life-time at the grain boundaries of larger nanoparticle agglomerates. 12 As of now, there is no general understanding of the phenomena attributable to the particle-size-triggered variation of the semiconductor photo-electrochemical activity. The only report in this respect represents a study on the photo-electrochemical activity of the SrTiO 3 nanocubes in the water oxidation reaction, which describes the size dependence of the photoelectrochemical behavior, free of particle shape or agglomeration effects.…”

Development and Functionalization of Visible-Light-Driven Water-Splitting Photocatalysts

“…To obtain highly active water-splitting photocatalysts, the exciton separation efficiency must be enhanced [ 288 ]. In future, fluorescence lifetime and transient absorption spectroscopic measurements [ 308 , 309 , 310 , 311 , 312 , 313 , 314 ] are expected to be conducted for a number of photocatalysts to gain a deeper understanding of the influence of the photocatalyst substrate, cocatalyst, and interfacial structure between them on the charge separation efficiency. Structural analysis of loaded cocatalysts.…”

Enhancing Photooxidative Performance with Bi2O3 Nanoparticle-Modified BiVO4 Heterostructural Flowers

“…However, the practical applications of BiVO 4 are still hindered by its low specific surface area and long-distance charge transport process in the bulk. 17,18 Therefore, a novel thin structure with a high surface area must be developed.…”

“…Then, chemical bonding with BiVO 4 was formed, subsequently trapping the photoexcited holes as photocatalytic oxidation sites and restricting the photoexcited carrier recombination. However, the practical applications of BiVO 4 are still hindered by its low specific surface area and long-distance charge transport process in the bulk. , Therefore, a novel thin structure with a high surface area must be developed.…”