<i>In Situ</i> Transformation of Tin Microparticles to Nanoparticles on Nanotextured Carbon Support Boosts the Efficiency of the Electrochemical CO₂ Reduction

Developing sustainable, efficient catalysts for the electrocatalytic reduction of CO₂ to valuable products remains a crucial challenge. Our research demonstrates that combining tin with nanostructured carbon support leads to a dynamic interface promoting the transformation of microparticles to nanoparticles directly during the reaction, significantly increasing the formate production up to 5.0 mol h^-1 g^-1, while maintaining nearly 100% selectivity. Correlative electrochemistry-electron microscopy analysis revealed that the catalyst undergoes an <i>in situ</i> self-optimization during CO₂ electroreduction. It has been found that changes in the catalyst are caused by the breakdown of Sn particles driven by electrochemical reactions. The process of pulverization typically results in a decrease in the catalytic activity. However, when Sn particles are pulverized and reach approximately 3 nm in size on the surface of the nanotextured carbon support, the efficiency of the catalyst is maximized. This enhancement occurs because the <i>in situ</i>-formed Sn nanoparticles exhibit better compatibility with the nanotextured support. As a result, the number of electrocatalytically active sites significantly increases, leading to a reduction in charge transfer resistance by more than 2-fold and an improvement in reaction kinetics, which is evidenced by changes in the rate-determining step. Collectively, these factors contribute to a 3.6-fold increase in the catalyst's activity while maintaining its selectivity for formate production.