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

Abstract

As an operando model system study for CO2 catalyst, PtGa(111) single crystal alloy is chosen to explore the CO2 adsorption properties of the PtGa alloy surface under elevated pressure of CO2 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 CO2 gas, the CO2 adsorption-derived species (CO2δ-, HCOO–) start to appear only after the CO2 gas pressure reaches 0.02 mbar, indicating a distinct pressure gap in CO2 adsorption/dissociation on PtGa alloy. As surface temperature increases to 400–500 K under 0.2 mbar, both CO2δ- and HCOO– species start to diminish while surface GaOx starts to increase. The concurrent reduction in surface work function likely stems from the dynamic interactions among surface GaOx, CO2δ–, and adsorbed C–H at their optimal coverage. Throughout the CO2 reaction, only Ga is oxidized while Pt remains metallic states, implying the important role of Ga oxide in CO2 reaction. © 2026 Elsevier B.V.