Recently, our center researchers Prof. Can Li, Post-doc Feng-tao Fang and Ph.D student Jian Zhu from DICP employed spatially resolved surface photovoltage spectroscopy (SRSPS) to obtain direct evidence for highly anisotropic photogenerated charge separation. The research also revealed the promoted effect of the built-in electric field in the space charge region of different facets on the anisotropic photoinduced charge transfer in a single semiconductor crystal. The results were published at Angew. Chem. Int. Ed.（http://dx.doi.org/10.1002/anie.201504135）

Photocatalytic water splitting is one of the most promising way to solve energy and pollution problems, while charge separation is the key to photocatalysis efficiency. Photoinduced charge separation on the nano to micrometer scale, with varying lifetimes, constitutes the key component of solar energy conversion devices. Prof. Li group have been working persistently on charge separation study. They synthesized a new catalyst CdS/MoS2 showed better water splitting performance than traditional Pt/CdS (J. Am. Chem. Soc., 2008, 130, 7176-7177).The first article about heterogeneous junction of TiO2 promotion effect in H2 evolution reaction was reported by the team in Angew. Chem. Int. Ed., 2012, 51, 13089-13092. Later, they also found that photogenrated electrons and holes can be separated between the different facets of BiVO4 photocatalyst. (Nature Comm., 2013,4,1432)

For a better understanding of the charge separation feature, the team used the application of spatially resolved surface photovoltage spectroscopy (SRSPS) to obtain direct evidence of highly anisotropic photogenerated charge separation on different facets of a single BiVO4 photocatalyst. Highly anisotropic photoinduced hole distribution is observed in single BiVO4 crystal with preferentially exposed {010} facets, and the surface photovoltage (SPV) signal intensity on the {011} facet is 70 times stronger than that on the {010} facet. The result provides insight into the nature of photogenerated charge separation in a single semiconductor photocatalyst particle and provides an exciting opportunity to optimize the performance of solar energy conversion devices by utilizing the anisotropic charge-transfer properties of single-crystal semiconductors.

This work was financially supported by the 973 National Basic Research Programme of the Ministry of Science and Technology (Grant 2014CB239403), the Key Research Program of the Chinese Academy of Sciences (CAS) and the Collaborative Innovation Center of Chemistry for Energy Materials (iChEM)