Identification of Metallic Nickel-Hydroxyl Interfaces as Active Sites for Efficient Catalytic CO₂ Hydrogenation

CO₂ hydrogenation to methane is a promising strategy for sustainable fuel production and carbon emission control. Ni-based catalysts are widely investigated for CO₂ methanation, while the exact nature of active sites is still controversial. Here, we show that the metallic Ni in conjunction with hydroxyl groups plays a determining role in CO₂ hydrogenation reaction. Keeping both the high proportion of Ni⁰ and the high amount of OH groups achieves excellent catalytic activity. Conversely, a decrease in either the proportion of Ni⁰ or the concentration of OH groups would result in a sharply decreased activity. We reveal that interfacial Ni⁰-OH sites are highly efficient for CO₂ adsorption and activation, which follows the key step of CO₂ hydrogenation to HCOO* and exhibits a lower barrier on the interfacial Ni⁰-OH sites than on the Ni⁰ sites. These findings provide essential insights into the identification of active sites on Ni-based catalysts for CO₂ hydrogenation and are pivotal for the design of highly active catalysts.