Molecular-level insights into CO2 activation on Ni(111) from in situ infrared spectroscopy

The activation of CO2 on nickel surfaces is the first step of various CO2 conversion processes. Consequently, understanding the surface intermediates formed during this step and their adsorption sites is crucial for elucidating reaction mechanisms. In this study, we employ in situ infrared spectroscopy to investigate the interaction of 1 mbar CO2 with a model Ni(111) catalyst between 25°C and 300°C. Under these conditions, CO2 is activated via a direct dissociation into CO and atomic oxygen, while the oxidation state of the Ni(111) surface is primarily determined by residual H2 and O2. The high surface coverage of CO and oxygen at ambient CO2 pressure induces a competitive adsorption mechanism on the energetically favored hollow sites. This mechanism leads to a temperature-dependent distribution of CO between top and hollow sites, potentially explaining the effect of reaction conditions on the adsorption site of CO intermediates in CO2 conversion reactions.