The influence of oxygen on the surface interaction between CO2 and copper studied by ambient pressure X-ray photoelectron spectroscopy

Copper materials are widely used in heterogeneous catalysis, including CO2 reduction, but the precise mechanisms and the oxidation states of Cu involved remain controversial. The surface chemistry at the interface between solid Cu and the CO2 containing gas phase lies at the heart of the complex pathways involved in the catalytic interaction. This paper utilizes the technique of ambient pressure X-ray photoelectron spectroscopy (APXPS) to probe the surface chemistry of polycrystalline Cu in a pure CO2 as well as a mixed CO2/O-2 atmosphere. Depending on the composition of the gas phase, distinct differences in both the oxidation state of the Cu surface as well as the composition and distribution of the carbon-containing products adsorbed to the metal surface are found. The addition of O-2 to the gas feed leads to oxidation of Cu to Cu2O leading to increased adsorbtion of oxygenated species. The presented results show how precise control over the sample environment enables insights into the chemistry of both the metal surface and the resulting adsorbed species at near-ambient pressures.