First-principles DFT study of structural, electronic and optical properties of Cu-doped TiO₂ (112) surface for enhanced visible-light photocatalysis

In this work, first-principles density functional theory (DFT) calculations are used to study the structural, electronic, and optical properties of pristine and Cu-doped TiO₂ (112) surface in oxygen-rich environment, and then compare the results to the bulk phase. We find the pristine (112) surface to be chemically and thermodynamically stable, exhibiting indirect band gap value of 2.89 eV. By 5.6% concentration of Cu-doping, the energy gap in the asymmetric spin bands and PDOS reaches a value of 2.00 eV, with induced magnetism. The visible range direct band gap in Cu-doped systems enhances the photo-absorption triggering the threshold value and the inter-band transitions by lowering the intensity of the dielectric constant, reflectance, and refractive index, making them suitable candidates for optoelectronics and photocatalytic applications.