Effect of silver doping on the electrocatalytic activity of CuS for CO₂ reduction to C₂ products

Electrochemical CO₂ reduction (eCO₂RR) is a promising route to convert CO₂ into valuable multicarbon (C₂) compounds. Numerous catalyst structures are designed to accelerate reaction kinetics and steer selectivity toward C₂ products. In this work, we synthesize CuS and Ag-doped CuS nanocomposites (5%, 10%, and 20% Ag) and test them as catalysts for CO₂ reduction. Electrochemical evaluation is performed in a H-type cell and a flow-cell setups, where the 20% Ag-doped CuS demonstrates excellent performance, delivering a Faradaic efficiency (FE) over 45% for C₂ products, particularly ethanol (C₂H₅OH) and ethylene (C₂H₄) at −1.4 V vs the reversible hydrogen electrode (RHE) and a total current density of 191 mA cm−2. This composition outperforms the other loadings in current density and shows a significant increase in C₂ product formation compared to single-metal CuS catalysts. Ag incorporation facilitates the CO₂ reduction pathway by promoting C-C coupling, favoring C₂ product formation over single-carbon (C₁) products such as CO and formic acid. These results highlight the significance of Ag doping in optimizing CuS-based catalysts for efficient CO₂ conversion, especially in the flow-cell configuration, which also demonstrates scalability toward high-efficiency eCO₂RR.