Defect‐Induced Raman Scattering in Cu₂O Nanostructures and Their Photocatalytic Performance

AbstractAdvanced oxidation processes using photogenerated charges in semiconductors constitute an approach to reduce and oxidize pollutants, with an efficiency that depends on the photo physics and defect chemistry of the photocatalyst. In this study, 2D Cu2O coatings on flat copper metal and on 3D copper nanopillars are created via low‐temperature oxidation and compared. The structures are characterized by X‐ray diffraction, Raman spectroscopy, and electron microscopy. The thickest surface oxide layers on the 3D structures show outgrowth of high‐aspect ratio CuO nano‐needles through the Cu2O layer, rationalized through a field‐induced copper ion diffusion mechanism. Raman scattering provides details about both the specific copper oxide phase present and the type and extent of defects, with a resolution spanning from hundreds of nanometers to micrometers. We show that defects in Cu2O induce Raman activity in several of its modes that are purely IR‐active or optically silent in pristine Cu2O. The experimental results are corroborated by linear response density functional theory (DFT) calculations for full vibrational mode analysis. The Cu‐supported 2D copper oxide systems exhibit effective photocatalytic performance at quite low probe pollution concentration (10 μM), while the 3D nanopillar structures enhance the photocatalytic efficiency by around 30 % compared to their planar counterpart under these conditions.