Giant Defect-Induced Effects on Nanoscale Charge Separation\nin Semiconductor Photocatalysts

Defects can markedly\nimpact the performance of semiconductor-based\nphotocatalysts, where the spatial separation of photogenerated charges\nis required for converting solar energy into fuels. However, understanding\nexactly how defects affect photogenerated charge separation at nanometer\nscale remains quite challenging. Here, using time- and space-resolved\nsurface photovoltage approaches, we demonstrate that the distribution\nof surface photogenerated charges and the direction of photogenerated\ncharge separation are determined by the defects distributed within\na 100 nm surface region of a photocatalytic Cu2O particle.\nThis is enabled by the defect-induced charge separation process, arising\nfrom the trapping of electrons at the near-surface defect states and\nthe accumulation of holes at the surface states. More importantly,\nthe driving force for defect-induced charge separation is greater\nthan 4.2 kV/cm and can be used to drive photocatalytic reactions.\nThese findings highlight the importance of near-surface defect engineering\nin promoting photogenerated charge separation and manipulating surface\nphotogenerated charges; further, they open up a powerful avenue for\nimproving photocatalytic charge separation and solar energy conversion\nefficiency.