Laser-engineered interfacial modulation of In, Sn, and InSn electrodes for enhanced electrochemical CO2 reduction

Electrochemical CO₂ reduction (EC CO₂RR) on p-block metals such as indium (In), tin (Sn), and their alloy (InSn) is a promising route for formate production. Here, we investigate how laser-induced interfacial tuning of oxidation states and surface structures modulates CO₂RR performance. Using 1064 nm laser ablation, we controlled the metal/metal oxide interface and evaluated its impact on activity, selectivity, and reaction kinetics across different laser intensities. Moderate laser treatment enhanced formate Faradaic efficiency up to 87.5 % by increasing electrochemical surface area, suppressing hydrogen evolution, and optimizing charge transfer properties. Electrochemical impedance spectroscopy revealed lower charge transfer resistance and higher double-layer capacitance for laser-treated electrodes, particularly under CO₂-saturated conditions. Under Ar condition, inductive loops emerged, indicating sluggish hydrogen adsorption dynamics, which were suppressed under CO₂ due to competitive *OCHO binding. XPS depth profiling showed dynamic modulation of surface oxidation states during CO₂RR, with InSn exhibiting the most stable and selective interface. This study highlights the crucial role of interfacial oxide–metal chemistry and surface restructuring in dictating CO₂RR pathways and kinetics, providing a design strategy for efficient formate-selective electrocatalysts.