Dopant effects on the environment-dependent chemical properties of NiO(100) surfaces

NiO is a promising material for applications such as electronic devices and catalysts due to its low cost, environmental friendliness, and optimal properties. Doping the NiO near surface structure can further tune material properties. Despite extensive studies on doped NiO (M-NiO), there remains a lack of connection between dopant, environment-dependent dominant near surface structures, and overall chemical properties. Here, the dopant effects on the surface structure and electronic properties of M-NiO(100) are systematically examined using density functional theory and ab initio phase diagrams. The simultaneous factors tested include dopant element (Al, Mo, Nb, Sn, Ti, V, W, or Zr), dopant placement (surface or subsurface), Ni/O vacancies (surface or subsurface), and oxygen adsorption. The results reveal the dominant surface structures and compositions of M-NiO(100) under a wide range of environmental conditions (i.e. temperature and pressure). Subsequent electronic analyses of the dominant M-NiO(100) structures shows non-uniform changes in charge redistribution, band gap, work function, and d-band center with dopant and near surface structure, emphasizing the role of dopants in tuning M-NiO(100) properties. Overall, these multiscale modeling results enable a rapid, effective, and a priori prediction of dominant M-NiO(100) surface structures with distinct chemical properties, crucial for guiding NiO-based materials design.