Excessive CO2 emissions has led to global warming. In contrast, transferring CO2 into fuels or useful chemicals can mitigate climate change caused by the greenhouse effect and achieve carbon recycling. Among the numerous conversion methods, electrocatalytic CO2 reduction reaction (CO2RR) is promising because the reaction conditions are moderate and the process can be powered by renewable energy produced by solar, wind, or other renewable sources. Most of the research in this field has focused on the converting CO2 into multi-carbon products (e.g. ethanol), as they are good candidates for replacing traditional fossil fuels. But combining CO2 reduction with heteroatoms (such as nitrogen) becomes more attractive because the such compounds (like urea or acetamide) are more valuable than multicarbon products. Moreover, carbon products with heteroatoms are also important raw materials for pharmaceutical and chemical industries, and even be utilized in agriculture. Cu-based catalysts have been widely applied for CO2RR to produce multicarbon products due to their moderate interactions with the reaction intermediate *CO. The unique inherent properties of Cu-based catalysts give them potential to be used to produce compounds with other heteroatoms. Compounds with C-S bonds such as hydroxymethanesulfonate (CH3NaO4S) are indispensable in biological and pharmaceutical domains, but their synthetic processes are complicated and need harsh reaction conditions. Using electrochemical method to drive the C-S bond formation is a promising route because the reaction can be conducted under ambient temperature and pressure, and the reaction steps are comparatively simple. Against this backdrop, we use CO2 and sulfite as substrates and Cu2O as electrocatalysts to synthesize CH3NaO4S as the product with a C-S bond. The optimized Faradaic efficiency of CH3NaO4S is 2.49% at -0.78 V vs. RHE. Although the selectivity of this reaction is modest, it is the first reported electrochemical synthesis CH3NaO4S and first heterogeneous electrochemical C-S coupling reaction. In-situ Raman experiments reveal that *CO is the key intermediate during the reaction. Our results provide a new avenue for CO2 fixation and are beneficial for organic compounds synthesis via green electrochemical methods.

Electrosynthesis of compounds with C-S bonds by using Cu-based electrocatalysts

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ACS Fall 2022

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