ReaxFF molecular dynamics study of early oxidation of nickel nanoparticles

Nickel nanoparticles (NPs) are widely used in many fields, but contact with oxygen leads to structural damage and degradation of their properties, so a comprehensive understanding of their oxidation mechanism is of great importance. In this work, we performed reactive molecular dynamics simulations to investigate the oxidation mechanism of Ni NPs. The results show that the oxidation of Ni NPs mainly includes the formation of surface oxide nuclei, oxide extension to form oxide layers covering the surface, and the inward growth of oxide layers. We have investigated the structure of the oxidation products and found that it consists of Ni–O tetrahedra interconnected by sharing one Ni atom. In addition, the effects of initial oxygen concentration, temperature, and humid environment on oxidation behavior are discussed. This work contributes to the understanding of the oxidation of Ni NPs at the atomic scale, which helps in the design of anti-corrosion of Ni NPs and the preparation of novel nickel oxides. Graphical abstract