CO₂ electroreduction at Au_xCu_1-x obtained by pulsed laser deposition in O₂ atmosphere

Au_xCu_1-x thin films were synthesized by pulsed laser deposition (PLD) and their electrocatalytic properties towards CO₂ reduction in aqueous solution were assessed. The presence of an O₂ atmosphere during the PLD process modified the chemical nature of the resulting Au_xCu_1-x films, with different oxide types identified by X-ray photoelectron spectroscopy. The impact of these oxides, and of the Cu/Au stoichiometry, on the partial current density and conversion efficiency were assessed. The formation of Au_xCu_1-x alloy thin films and/or the introduction of an O₂ atmosphere during deposition does not yield to any marked increase of the formation of carbonaceous compounds, and CO and H₂ were the only two products formed, along with formate detected in trace amounts ( < 1%). Oxide-derived Au catalysts obtained by PLD under O₂ atmosphere do not alter CO₂ selectivity towards CO formation. High copper content catalysts deposited in vacuum exhibit the lowest overall CO FE%, while increasing the Au content enhances it. The same trend is observed for Au_xCu_1-x catalysts deposited under 2 and 220 mTorr O₂, aside from the fact that increasing Cu content under high O₂ pressure has a less negative influence on CO FE%.