Cu Based Dilute Alloys for Tuning the C2+ Selectivity of Electrochemical CO2 Reduction

Abstract

Electrochemical CO₂ reduction is a promising technology for replacing fossil fuel feedstocks in the chemical industry but further improvements in catalyst selectivity need to be made. So far, only copper-based catalysts have shown efficient conversion of CO₂ into the desired multi-carbon (C₂₊) products. This work explores Cu-based dilute alloys to systematically tune the energy landscape of CO₂ electrolysis toward C₂₊ products. Selection of the dilute alloy components is guided by grand canonical density functional theory simulations using the calculated binding energies of the reaction intermediates CO*, CHO*, and OCCO* dimer as descriptors for the selectivity toward C₂₊ products. A physical vapor deposition catalyst testing platform is employed to isolate the effect of alloy composition on the C₂₊/C₁ product branching ratio without interference from catalyst morphology or catalyst integration. Six dilute alloy catalysts are prepared and tested with respect to their C₂₊/C₁ product ratio using different electrolyzer environments including selected tests in a 100-cm² electrolyzer. Consistent with theory, CuAl, CuB, CuGa and especially CuSc show increased selectivity toward C₂₊ products by making CO dimerization energetically more favorable on the dominant Cu facets, demonstrating the power of using the dilute alloy approach to tune the selectivity of CO₂ electrolysis.

Keywords: alloy; catalyst morphology; copper catalyst; density functional theory; electrochemical CO2 reduction; energy efficiency; physical vapor deposition.