A density functional theory analysis on syngas adsorption on NiO (100) surface

Oxygen carrier (OC) design can effectively improve the performance of chemical looping combustion (CLC) and realize fossil fuel combustion at low energy-cost CO2 capture. This study describes the adsorption principles of syngas (i.e. CO and H-2) on a clean nickel oxide (100) surface under single and multiple nearest neighbor effects. The results show that the adsorption stability of CO and H-2 is mostly weakened by the first neighbor compared to the rest. With the same species as nearest neighbors (uniform adsorption), syngas adsorption stability is reduced when the number of neighbors increases. Similarly, when compared to uniform adsorption, the adsorption stability of CO and H-2 is slightly stronger with neighboring sites occupied with different species (hybrid adsorption). In addition, a lower degree of symmetry tends to strengthen CO and H-2 adsorption. Results from this analysis show that the adsorption stability of CO and H-2 with neighbors are highly related to steric, hybrid and symmetry effects. An electronic property analysis was performed to further support the key role of hybrid neighboring effects in the adsorption process of syngas on the nickel oxide (100) surface.