Charge separation via asymmetric illumination in photocatalytic Cu2O particles


Solar-driven photocatalytic reactions provide a potential route to sustainable fuels. These processes rely on the effective separation of photogenerated charges, and therefore understanding and exploring the driving force for charge separation is key to improving the photocatalytic performance. Here, using surface photovoltage microscopy, we demonstrate that the photogenerated charges can be separated effectively in a high-symmetry Cu2O photocatalyst particle by asymmetric light irradiation. The holes and electrons are transferred to the illuminated and shadow regions, respectively, of a single photocatalytic particle. Quantitative results show that the intrinsic difference between electron and hole mobilities enables a diffusion-controlled charge separation process, which is stronger than that caused by conventional built-in electric fields (40 mV versus 10 mV). Based on the findings, we assemble spatially separated redox co-catalysts on a single photocatalytic particle and, in doing so, enhance the performance for a model photocatalytic reaction by 300%. These findings highlight the driving force caused by charge mobility differences and the use of asymmetric light illumination for charge separation in photocatalysis.

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Fig. 1: Charge separation between the illuminated facet and shadow facet under asymmetric illumination.
Fig. 2: Impact of illumination symmetry on the charge separation.
Fig. 3: Homogeneous charge separation by built-in electric fields.
Fig. 4: Quantitative SPV analysis and theoretical simulation to understand diffused charge separation.
Fig. 5: Asymmetric co-catalyst assembly and its impact on charge separation.


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This work was supported by the National Natural Science Foundation of China (grant no. 21633015, 21773228), the National Key Basic Research Program of China (973 Program, grant no. 2014CB239403) and the Strategic Priority Research Program and Equipment Development Project of the Chinese Academy of Sciences, grant no. XDB17000000, YJKYYQ20170002.

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R.C. conceived and conducted most of experiments, and analysed data; S.P. conducted the theoretical simulation; H.A. analysed the SPV data and conducted Raman measurements; J.Z. helped in the SPVM measurements; S.Y. helped in the activity measurements; Y.G. analysed KPFM data; F.F. conceived most of the experiments and analysed data. The manuscript was written by R.C. and F.F.; C.L. proposed the project, analysed data and revised the manuscript.

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Correspondence to Fengtao Fan or Can Li.

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Chen, R., Pang, S., An, H. et al. Charge separation via asymmetric illumination in photocatalytic Cu2O particles. Nat Energy 3, 655–663 (2018).

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