Unraveling Charge-Separation Mechanisms in Photocatalyst Particles by Spatially Resolved Surface Photovoltage Techniques.

The photocatalytic conversion of solar energy offers a potential route to renewable energy, and its efficiency relies on effective charge separation in nanostructured photocatalysts. Understanding the charge-separation mechanism is key to improving the photocatalytic performance and this has now been enabled by advances in the spatially resolved surface photovoltage (SRSPV) method. In this Review we highlight progress made by SRSPV in mapping charge distributions at the nanoscale and determining the driving forces of charge separation in heterogeneous photocatalyst particles. We discuss how charge separation arising from a built-in electric field, diffusion, and trapping can be exploited and optimized through photocatalyst design. We also highlight the importance of asymmetric engineering of photocatalysts for effective charge separation. Finally, we provide an outlook on further opportunities that arise from leveraging these insights to guide the rational design of photocatalysts and advance the imaging technique to expand the knowledge of charge separation.