(89a) Photogenerated Charge Separation in Artificial Photosynthesis Systems

This lecture presents the research progress on solar fuel productions from artificial photosynthesis, namely photocatalysis and photoelectrocatalysis (PEC) processes with the emphasis on the photogenerated charge separation.

The great challenge of energy conversion photocatalysis lies in its complicated processes including light absorption (harvesting), charge separation and migration, and catalytic reactions. In order to gain high photon energy conversion efficiency, a photocatalyst or photocatalytic system must harmonically guarantee high efficiencies of all these three processes instead one of them. Semiconductors with appropriate phase junctions have been demonstrated to be an efficient approach for achieving efficient charge separation [1]. Cocatalysts play important roles in the assembly of efficient semiconductor photocatalyst. It has been conceptually demonstrated Pt-PdS/CdS dual cocatalyst system can achieve 93% H₂ evolution activity in the presence of sacrificial reagents under visible light irradiation (λ>420 nm) [2,3]. Recently, it has been also demonstrated that electrons and holes can be spatially separated on the {010} and {110} facets of BiVO₄ crystal [4]. This finding has been demonstrated to be general for a number of catalytic systems including SiTiO₃, Cu₂O and TiO₂. It has been demonstrated that the intrinsic nature of charge separation between different facets of BiVO₄ together with the synergetic effect of dual-cocatalysts plays key role in photocatalytic activity enhancement [5]. Spatially resolved surface photovoltage spectroscopy (SRSPS) characterization on the photogenerated charge separations on different facets of a single BiVO₄ photocatalyst shows that the surface photovoltage signal intensity on the {011} facet can be up to 70 times stronger than that on the {010} facets[6]. This reveals that the nature 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.

References:

 

[1] X.Wang, H.X. Han, and C. Li, et al. Angew. Chem. Intd. Ed. 2012, 51, 13089.

[2] H. J. Yan, J. H. Yang and C. Li, et al. J. Catal. 2009, 266, 165.

[3] J. H. Yang, H. X. Han, and C. Li, et al. Acc.Chem.Res, 2013, 46, 1900.

[4] R. G. Li, F. X. Zhang and C. Li, et al. Nature. Commun. 2013, 4: 1432.

[5] R.G. Li, H. X. Han and C. Li, et al. Energy Environ. Sci. 2014, 7, 1369.

[6] J. Zhu, F.T. Fan, R. T. Chen and C. Li, et al. Angew. Chem. Int. Ed. 2015,

54, 9111.