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

Abstract

Electrochemical conversion of CO 2 into useful chemicals is a promising approach for transforming CO 2 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 CO 2 reduction reaction (CO 2 RR) 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 CO 2 to CO in excess of 6 mA cm −2 at a Faradaic efficiency of ∼99% in aqueous electrolytes (50 mM K 2 CO 3 saturated with CO 2 ). 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 CO 2 RR and offer an interesting architecture for highly selective electrocatalysis capable of sustaining high catalytic currents over prolonged periods.

Flexible Honeycombed Nanoporous/Glassy Hybrid for Efficient Electrocatalytic Hydrogen Generation

“…[12][13][14][15][16][17] The uniform bicontinuous nanoporosity produced by dealloying/etching can offer nanoporous materials satisfactory electrocatalytic activities, high-efficiency electron transportation, and improved selectivity for various redox reactions. [12][13][14][15][16][17] The uniform bicontinuous nanoporosity produced by dealloying/etching can offer nanoporous materials satisfactory electrocatalytic activities, high-efficiency electron transportation, and improved selectivity for various redox reactions.…”

“…Recently, free-standing 3D nanoporous materials have attracted close attention owing to their outstanding performance in catalysis. [12][13][14][15][16][17] The uniform bicontinuous nanoporosity produced by dealloying/etching can offer nanoporous materials satisfactory electrocatalytic activities, high-efficiency electron transportation, and improved selectivity for various redox reactions. [18,19] To date, numerous nanoporous materials, especially nanoporous transition metals and their oxides, have been reported for efficient catalysts toward HER in alkaline electrolyte.…”

Nano-Folded Gold Electrocatalysts Enhance the Selectivity of Carbon Dioxide Reduction

“…Both are significantly higher than Au-0, which has a jCO of 0.51 mA/cm 2 Au. This result suggests that roughness does play a role in the performance of nano-folded catalysts, as expected, 15,17,18 but cannot explain the entire increase in jCO. The measurement also yields surface roughness factors, which indicates a roughness factor of 2.1 for Au-70, 1.3 for Au-30 and 1 for Au-0 (Table S1).…”

“…From prior literature, it is known that a higher local pH at the catalyst interface suppresses the HER reaction, which would improve the FECO and agrees with our findings. 15,17,18 In summary, we have demonstrated a new strategy to enhance the selectivity of CO formation by utilizing nano-folded Au catalysts for CO2 reduction. The catalysts can be made in a straightforward manner using a pre-strained polymer substrate.…”

“…Aside from the increase in surface area, we attribute the enhancement of the selectivity of Au-70 to a local pH effect. 15,17,18 We simulated the pH at the interfaces of the catalysts using the effective diffusivities of [CO2]aq, HCO3 -, CO3 2and OHand a previously reported mass transport model. [43][44][45] In the model, the effective diffusivity in porous media is given as 9 = , = => ?…”