Combinatorial Synthesis of Gold-Based Thin Films for Improved Electrocatalytic Conversion of CO2 to CO

Carbon dioxide electroreduction (CO2ER) was studied on 35 gold-based thin film catalysts sputtered on glassy carbon disks. A sputter-down setup was used for the deposition of these thin films in a combinatorial manner. Zinc and silver were employed in combination with gold in order to obtain new catalysts. Linear sweep voltammetry was employed to obtain the selectivity profile of each catalyst. Among the 35 catalysts, three ternary combinations (Au14Ag34Zn52, Au32Ag51Zn17, and Au16Ag10Zn74) and one binary combination (Au80Zn20) were identified as being active catalysts, reducing the dissolved CO2 in favor of proton reduction. Two ternary catalysts (Au16Ag10Zn74 and Au32Ag51Zn17) exhibited higher selectivity and lower overpotential for CO2ER than the pure metals. The Au80Zn20 binary catalyst exhibited the longest potential range where the selectivity for CO2ER remains constant. A decrease of the gold loading between 18 and 88 % was obtained for these catalysts, suggesting that they are promising candidates for an industrial application of CO2ER. Electrochemical impedance spectroscopy proved that the mechanism of CO2ER, involving two successive one-electron transfers, is identical on pure metals and combined sputtered catalysts.