Regulating the selectivity of CO₂ electroreduction on Cu-Sn alloy nanofilm via Facile magnetron sputtering

Cu-based catalysts have demonstrated significant potential for the electrochemical CO₂ reduction reaction (CO₂RR) due to their moderate adsorption energy for reaction intermediates. However, further optimization of product selectivity remains essential. In this study, Cu was alloyed with Sn by magnetron sputtering to improve the selectivity for HCOOH. A series of morphological and structural characterizations, along with electrocatalytic performance tests were systematically performed on Cu-Sn alloy. It was found that at a Sn atomic ratio of 20.63%, the Cu₄₁Sn₁₁ alloy formed, exhibiting the highest selectivity for HCOOH with a Faraday efficiency of 74%. Experimental results and DFT calculations indicated that alloying increased the electron density around Cu and lowered the Work Function, thereby enhancing electron transfer. The incorporation of Sn shifted the d-band center downward and adjusted the intermediate adsorption energy to an optimal level, thereby facilitating the CO₂-to-HCOOH conversion process. The calculations of ΔG for each reaction step revealed that the energy barrier for CO₂-to-HCOOH conversion process was lowered on the Cu-Sn alloy surface, while the barriers for HER and CO₂-to-CO conversion process were increased, leading to the enhanced selectivity of HCOOH. This study is valuable for the further development of Cu-based alloy catalysts for CO₂RR.