Thickness- and Particle-Size-Dependent Electrochemical Reduction of Carbon Dioxide on Thin-Layer Porous Silver Electrodes

The electrochemical reduction of CO₂ can not only convert it back into fuels, but is also an efficient manner to store forms of renewable energy. Catalysis with silver is a possible technology for CO₂ reduction. We report that in the case of monolithic porous silver, the film thickness and primary particle size of the silver particles, which can be controlled by electrochemical growth/reduction of AgCl film on silver substrate, have a strong influence on the electrocatalytic activity towards CO₂ reduction. A 6 μm thick silver film with particle sizes of 30–50 nm delivers a CO formation current of 10.5 mA cm⁻² and a mass activity of 4.38 A g_Ag⁻¹ at an overpotential of 0.39 V, comparable to levels achieved with state-of-the-art gold catalysts.