Sn-M (M=Sn, Bi, In) Bimetallic Catalysts for Electrocatalytic Conversion of CO2 to Formic Acid

Abstract

Carbon dioxide is a gas found in the atmosphere, produced primarily through natural processes such as the respiration of plants and animals, the decomposition of organic matter, and the breakdown of living organisms. However, the natural carbon cycle has been significantly disrupted by anthropogenic CO2 emissions, contributing to climate change. To mitigate the impact of elevated CO2 levels, efforts have been made to develop an artificial carbon cycle that captures atmospheric as well as anthropogenic CO2 and converts it into value-added chemicals. Among these, liquid organic hydrogen storage materials have gainedattention for their ease of handling and potential to store and release hydrogen (ondemand)efficiently. Formic acid has emerged as a promising candidate for this purpose due to its ability to act as a hydrogen carrier under mild conditions. One of the most effective yet challenging methods to convert CO2 into formic acid is through electrochemical reduction. This process requires highly selective and stable catalysts, and recent research has highlighted the efficiency of Snbasedbimetallic alloys for this application. Metals such as Sn, In, and Bi, which belong to the p-block of the periodic table, have shown the ability to selectively produce formate through the electrochemical reduction of CO2. By combining two of these metals, it is possible to enhance their catalytic performance, leading to increased production rate of the desired product.This study focuses on the development of Sn-based bimetallic alloy electrodes through straightforward preparation methods such as electrodeposition and dropcasting of a secondary metal-oxide ink onto a Sn substrate. The prepared electrodes were characterized using X-ray diffraction (XRD), linear sweep voltammetry (LSV), and cyclic voltammetry (CV).The catalytic performance of all electrodes was evaluated, and the results indicate that bimetallic alloys exhibit significantly higher Faradaic efficiency (FE) at lower overpotentials compared to bulk Sn electrodes. Moreover, the dropcasting method demonstrated greater reproducibility in electrode preparation, further enhancing the overall performance in formic acid production.