Understanding and modulating the interaction between various reactive molecules and oxygen carriers are the key issue to achieve process intensification of chemical looping technology. C1 chemical molecules play an important role in many reactions involved with chemical looping processes. However, up to now, there is still a lack of systematic and in-depth understanding of the adsorption mechanism of C1 molecules on the surface of oxygen carriers (OCs). In this work, the intrinsic interaction between a series of C1 molecules composed of CH4, CO, CO2, CH3OH, HCHO and HCOOH and surface of NiO OCs in the chemical looping process have been studied using density functional theory calculations. Various adsorption configurations of Cl molecules and also different adsorption sites of NiO have been considered. The structural features of stable configuration of C1 molecules on the surface of NiO OCs have been obtained. Further, the interacted sites, types and strengths of Cl molecules on the surface of NiO have been directly pictured by the independent gradient model methods. Also, the nature of the interaction between C1 molecule and NiO surface has been investigated with the aid of energy decomposition analysis from a quantitative view. (C) 2020 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.