First-principles calculation based on DFT is performed to explore the structural, electronic and optical properties of monatomic Au or Cl adsorption on the bridge and fourfold hollow site of the 1I-terminated BiOI (0 0 1) surface. The results indicate that Au/BiOI and Cl/BiOI adsorption systems not only possess the better structural stability but also exhibit the perfect utilization of the visible light. The range of visible light utilization is broadened after Au or Cl adsorption at the B and H sites thus the photocatalytic performance can be improved. Au adsorption at H site shows the best photocatalytic performance and structural stability. (C) 2018 Elsevier B.V. All rights reserved.