Tuning the wettability of tandem electrodes affects CO2 electro-conversion to multicarbon products

Abstract

The tandem catalyst configuration has emerged as an effective strategy for enhancing the electrochemical conversion of CO₂ into multicarbon (C₂₊) products by incorporating a CO-producing layer with a Cu catalyst. While numerous catalyst combinations have been explored to optimize performance, the role of binders within the catalytic layers of such tandem structures has been underappreciated, despite their significant influence on the microenvironment, thereby markedly affecting product selectivity. In this study, a tandem electrode comprising a CO-producing Ag layer atop a Cu layer was fabricated and its CO₂ conversion performance was evaluated, focusing on the impact of binder wettability on C₂₊ production. Hydrophobic Cu layers outperformed their hydrophilic counterparts, exhibiting higher C₂₊ conversion rates and current densities. Notably, the C₂₊/CO ratios of the hydrophobic Cu-based electrodes varied significantly depending on the binder wettability of the CO-producing layer. The optimal configuration was found to be a hydrophilic CO-producing layer paired with a hydrophobic Cu layer, affording the highest C₂₊ partial current density of 220 mA cm^–2. The variation in the C₂₊/CO ratio was attributed to differences in the water accessibility, primary proton source, and CO utilization within the Cu layer, as revealed by controlled modifications of the tandem electrode microenvironment. These findings highlight the pivotal role of binder wettability in optimizing CO₂-to-C₂₊ conversion, offering a viable strategy for enhancing the CO₂ reduction reaction performance.