Tuning the pore structure of porous tin foam electrodes for enhanced electrochemical reduction of carbon dioxide to formate

Tin-based catalysts have been regarded as a promising candidate for electrochemical reduction of CO₂ to produce value-added chemicals and reduce CO₂ emissions. However, the catalysts still suffer from unsatisfied performance like large overpotential, rapid deactivation, and lower stability. In this work, the tunable pore structure of porous Sn foam electrodes were prepared using a simple acetic acid (bubble stabilizer)-assisted hydrogen bubble dynamic template method and evaluated as electrocatalysts for CO₂ reduction. The Sn-0.15 (bubble stabilizer concentration of 0.15 M in precursor electrolyte), characterized by pore diameter of 50–60 µm and 3.2 times higher of pore number on surface layer of electrode, exhibited an excellent activity towards CO₂-to-formate conversion with high Faradaic efficiency in a wide potential from −1.2 to −1.8 V, and acquired the maximum of 95.6% at −1.6 V vs. Ag/AgCl. With this porous electrode, formate started to produce at overpotentials as low as 473 mV and showed negligible degradation over electrolysis for 55 h. Electrochemical tests indicated the notable activity was attributed to the coordinative effect of enlarged reaction sites, weakened interaction strength of CO₂^[rad]− on the low-coordination sites, and alleviated reactant transfer resistance at reaction interfaces. These results demonstrate that tuning pore structure of tin catalyst is a convenient and promising approach for efficient CO₂ electroreduction.