Atomic Layer Deposition of Cu Electrocatalysts on Gas Diffusion Electrodes for CO₂ Reduction

Electrochemical reduction of CO₂ using Cu catalysts enables the synthesis of C₂₊ products including C₂H₄ and C₂H₅OH. In this study, Cu catalysts were fabricated using plasma-enhanced atomic layer deposition (PEALD), achieving conformal deposition of catalysts throughout 3-D gas diffusion electrode (GDE) substrates while maintaining tunable control of Cu nanoparticle size and areal loading. The electrochemical CO₂ reduction at the Cu surface yielded a total Faradaic efficiency (FE) > 75% for C₂₊ products. Parasitic hydrogen evolution was minimized to a FE of ∼10%, and a selectivity of 42.2% FE for C₂H₄ was demonstrated. Compared to a line-of-sight physical vapor deposition method, PEALD Cu catalysts show significant suppression of C₁ products compared to C₂₊, which is associated with improved control of catalyst morphology and conformality within the porous GDE substrate. Finally, PEALD Cu catalysts demonstrated a stable performance for 15 h with minimal reduction in the C₂H₄ production rate.