Spatial separation of photogenerated electrons and holes among {010} and {110} crystal facets of BiVO4

Abstract

Charge separation is crucial for increasing the activity of semiconductor-based photocatalysts, especially in water splitting reactions. Here we show, using monoclinic bismuth vanadate crystal as a model photocatalyst, that efficient charge separation can be achieved on different crystal facets, as evidenced by the reduction reaction with photogenerated electrons and oxidation reaction with photogenerated holes, which take place separately on the {010} and {110} facets under photo-irradiation. Based on this finding, the reduction and oxidation cocatalysts are selectively deposited on the {010} and {110} facets respectively, resulting in much higher activity in both photocatalytic and photoelectrocatalytic water oxidation reactions, compared with the photocatalyst with randomly distributed cocatalysts. These results show that the photogenrated electrons and holes can be separated between the different facets of semiconductor crystals. This finding may be useful in semiconductor physics and chemistry to construct highly efficient solar energy conversion systems.

Facet‐Controlled Synthetic Strategy of Cu2O‐Based Crystals for Catalysis and Sensing

“…Recently, numerous studies are focused on the formation of heterogeneous structures by rational growing supported substances (typically noble metal nanoparticles) on the support (typically metal oxides), since metal oxides can not only serve as a support for a better dispersibility of disperse metal nanoparticles (NPs), but also enhance the catalytic abilities by interacting with the metal NPs 6, 27, 30, 33, 36, 40, 50, 61, 145, 146, 147. Despite many successful examples on the synthesis of heterogeneous structures, it is noteworthy that the spatially controllable deposition of noble metal NPs on metal oxide support is a significant topic.…”

“…It is noteworthy that, although high‐index facets that have high‐density atomic edges with corners and plentiful unsaturated active sites are promising for catalysis and sensing applications, those facets are often unstable, and hardly obtained by traditional chemical methods 17, 18, 19, 20, 21, 22, 23. Thus, the shape‐dependent catalysis and sensing behaviours is primarily focused on NCs enclosed by low‐index facets, especially the three basic facets (i. e., the {100}, {111}, and {110} facets) 6, 7, 8, 9, 12, 13, 14, 16, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34. For instance, by employing hydrofluoric acid as a capping agent (CA), H. G. Yang et al34 were the first to obtain uniform anatase TiO 2 single crystals with a high percentage (47%) of highly reactive {001} facets, which possessed promising applications in sensors, solar cells and photocatalysis.…”

“…For instance, by employing hydrofluoric acid as a capping agent (CA), H. G. Yang et al34 were the first to obtain uniform anatase TiO 2 single crystals with a high percentage (47%) of highly reactive {001} facets, which possessed promising applications in sensors, solar cells and photocatalysis. Besides the various routes for the synthesis of NCs, several novel strategies have recently exploded by carving, modifying, or transforming the original NCs that greatly improve the catalysis and sensing performances 6, 27, 30, 33, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52. For example, X. Chen et al51 disordered the surface layers of nanophase TiO 2 by hydrogenation.…”

Hot‐Electron‐Mediated Photochemical Reactions: Principles, Recent Advances, and Challenges

“…To improve the performance of the semiconductor-based water splitting reaction, researchers have proposed numerous strategies for designing more efficient photocatalysts, e.g., by forming nanoscale heterojunctions, modulating the size, shape, and crystal structure of photocatalysts, and doping additional elements. [107][108][109][110][111][112][113][114] These strategies can provide highly efficient photocatalysts for the water splitting reaction by inhibiting the recombination of electronhole pairs, reducing and optimizing the migration distance of charge carriers, and tuning the band structure. However, these impressive achievements are still not adequate enough to be applied for practical use.…”

Rate Law Analysis of Water Oxidation and Hole Scavenging on a BiVO4 Photoanode

“…[21][22] It has also been reported that the photoelectrochemical reactivity of BiVO4 can be strongly modulated by the exposed crystal facet. 23 We have recently reported a rate law analysis of the kinetics of water oxidation on hematite photoanodes as a function of the density of surface accumulated valence band holes. This study showed a transition from 1 st order behavior at low light flux to 3 rd order at higher light fluxes.…”