Operando study of CO2 adsorption on PtGa(111) surface with ambient pressure XPS

As an operando model system study for CO 2 catalyst, PtGa(111) single crystal alloy is chosen to explore the CO 2 adsorption properties of the PtGa alloy surface under elevated pressure of CO 2 using ambient pressure X-ray photoelectron spectroscopy (AP-XPS). During surface cleaning process under UHV, i.e., sputtering and high temperature annealing process, considerable surface compositions changes are observed. When the PtGa alloy is exposed to CO 2 gas, the CO 2 adsorption-derived species (CO 2 δ-, HCOO – ) start to appear only after the CO 2 gas pressure reaches 0.02 mbar, indicating a distinct pressure gap in CO 2 adsorption/dissociation on PtGa alloy. As surface temperature increases to 400–500 K under 0.2 mbar, both CO 2 δ- and HCOO – species start to diminish while surface GaO x starts to increase. The concurrent reduction in surface work function likely stems from the dynamic interactions among surface GaO x , CO 2 δ– , and adsorbed C–H at their optimal coverage. Throughout the CO 2 reaction, only Ga is oxidized while Pt remains metallic states, implying the important role of Ga oxide in CO 2 reaction.