Nanoporous Gold as a Highly Selective and Active Carbon Dioxide Reduction Catalyst

Electrochemical conversion of CO2 into useful chemicals is a promising approach for transforming CO2 into sustainably produced fuels and/or chemical feedstocks for industrial synthesis. We report that nanoporous gold (np-Au) films, with pore sizes ranging from 10 to 30 nm, represent promising electrocatalytic architectures for the CO2 reduction reaction (CO2RR) due to their large electrochemically active surface area, relative abundance of grain boundaries, and ability to support pH gradients inside the nanoporous network. Electrochemical studies show that np-Au films support partial current densities for the conversion of CO2 to CO in excess of 6 mA cm–2 at a Faradaic efficiency of ∼99% in aqueous electrolytes (50 mM K2CO3 saturated with CO2). Moreover, np-Au films are able to maintain Faradaic efficiency greater than 80% for CO production over prolonged periods of continuous operation (110 h). Electrocatalytic experiments at different electrolyte concentrations demonstrate that the pore diameter of nanoporous cathodes represents a critical parameter for creating and controlling local pH gradients inside the porous network of metal ligaments. These results demonstrate the merits of nanoporous metal films for the CO2RR and offer an interesting architecture for highly selective electrocatalysis capable of sustaining high catalytic currents over prolonged periods.