Controlling Product Distribution of CO₂ Reduction on CuO-Based Gas Diffusion Electrodes by Manipulating Back Pressure

The electrochemical reduction reaction of CO₂ (CO₂RR) is a promising avenue toward the renewable energy-driven transformation of a greenhouse gas toward fuels and value-added chemicals. While copper uniquely can catalyze this reaction to longer carbon chains, Cu-based electrodes continue to face numerous challenges, including low selectivity toward desired products and poor stability. To unlock its potential for large-scale industrial implementation, great interest is shown in tackling these challenges, primarily focusing on catalyst and electrode modifications and thereby leaving a research gap in the effects of operation conditions. Herein, back pressure application is introduced in CO₂ electrolyzers at industrially relevant current densities (200 mA cm⁻²) in order to steer selectivity toward C₂₊ products. The back pressure adjusts CO₂ availability at the electrode surface, with a high CO₂ surface coverage achieved at ΔP = 130 mbar suppressing the competing hydrogen evolving reaction for 72 h and doubling of stable ethylene production duration. Faradaic efficiency of 60% for C₂₊ products and overall C₂₊ conversion efficiency of 19.8% are achieved with the easily implementable back pressure operation mode presented in this study. It is proven to be a promising tool for product selectivity control in future upscaled Cu-based CO₂ electrolysis cells.