Decoupling multiscale morphological effects in templated porous Ag electrodes for electrochemical CO₂ reduction

Electrochemical reduction of CO₂ using renewable electricity is a promising strategy to produce sustainable fuels and chemical feedstocks. The use of porous electrodes is a promising approach to increase the activity of electrocatalysts such as Ag which exhibit high CO selectivity. However, it is challenging to fully understand the impact of their complex morphologies. We varied electrodeposition conditions to obtain different micrometer-scale morphologies: flat catalysts and more dendritic (“coral”) catalysts. Performing this electrodeposition in either the absence or the presence of a template, allowed to independently introduce additional porosity of 180 nm cages connected via smaller windows. The structures were relatively stable in catalysis, with some changes on the 10 nm scale at the most negative potentials. The templated Ag catalysts consistently reached higher CO partial current densities than non-templated equivalents. Interestingly, where CO production scaled with the internal electrode surface area, simultaneous H₂ evolution was impeded in the mesoscale pore network. Therefore, our work shows a promising assembly strategy to deconvolute morphology effects on different length scales, and demonstrates the importance of porosity specifically at the 100 nm scale to enhance CO₂ conversion to CO in porous Ag electrodes.