Screening binary alloys for electrochemical CO2 reduction towards multi-carbon products

Abstract

Electrochemical reduction of CO₂ (eCO₂R) to high-value chemicals presents an attractive approach for utilizing CO₂. Copper (Cu) is presently the only electrocatalyst that fulfills this purpose with notable activity, but selectivity remains a problem. To identify catalysts for eCO₂R with high selectivity towards multicarbon (C₂₍₊₎) products, we explore binary systems composed of strongly and weakly CO binding metals alloyed with Cu, Fe, Co, Ni, and Pd. A total number of 142 alloys with two commonly studied configurations, L1₂ and L1₀, are simulated with density functional theory (DFT). We leverage recent progress in the atomistic understanding of the eCO₂R mechanism and use the binding energies of CO* and C* as descriptors when screening for C₂₍₊₎ selectivity. We evaluate the stability of the binary alloys by analyzing the formation energy of the clean alloy surfaces. Our theoretical screening identifies about 16 Cu-based alloys and 18 non-Cu based alloys with optimal C₂₍₊₎ selective properties for eCO₂R. For the non-Cu based binary alloys, the p-block elements play an important role in tuning the C* and CO* adsorption energies. In terms of stability, most of the Cu-based systems alloyed with metals that exhibit strong CO* binding are unstable. Ni-based alloys are more stable than the Co-based alloys followed by the Fe-based alloys, and all the Pd-based alloys are stable. In general, the L1₀ structural Fe, Co, Ni, and Pd-based alloys are more stable than the corresponding L1₂ alloys. Our approach identifies materials known to have good C₂₍₊₎ selectivity, but it also proposes several other promising materials that have not previously been tested for eCO₂R.