Synergistic Effect of Cu–Ag Bimetallic Catalysts in Boosting the electrochemical reduction of CO₂

The urgent need to address global warming has intensified research into technologies that convert CO₂ into value-added chemicals. Among the most promising products are hydrocarbons, particularly multi-carbon (C₂₊) compounds, which serve as sustainable energy carriers. Copper stands out as a key catalyst in this transformation due to its unique ability to facilitate C–C bond formation. In this study, we explore thermally evaporated copper-based alloy layers as efficient electrocatalysts for CO₂ reduction in a flow reactor system. By incorporating silver in controlled amounts, we fine-tune the surface properties and electronic structure of copper to enhance catalytic selectivity and stability. The thermal evaporation technique enables precise control over catalyst thickness and morphology on gas diffusion electrodes (GDEs), which are critical for performance. Our findings highlight copper's predominant influence in the formation of C₂₊ products, whereas silver plays a key role in enhancing the structural and operational durability of the Cu–Ag@GDE system. We conducted a systematic investigation into the electrocatalytic performance of thermally evaporated copper-based alloy layers for CO₂ reduction in a flow cell setup, with particular emphasis on the role of silver as a modifying element. Copper, known for its unique ability to catalyse the formation of C₂₊ hydrocarbons, was alloyed with varying amounts of silver to examine effects on activity, selectivity, and stability. Experiments at current densities between –150 and –190 mA/cm² revealed that incorporating silver into the Cu matrix enhanced product selectivity toward multi-carbon compounds and improved catalyst durability. Faradaic efficiencies were quantified via GC-MS/TCD and charge analysis, while structural and compositional properties were characterized using XRD, WD-XRF, FTIR, SEM, and profilometry. The Cu-dominant alloy catalysts retained structural integrity and consistent CO₂ electroreduction performance over 240 minutes of continuous operation, reinforcing the central role of copper and the synergistic contribution of silver.