Controlling the C1/C2+ product selectivity of electrochemical CO2 reduction upon tuning bimetallic CuIn electrocatalyst composition and operating conditions

Abstract

Electrochemical carbon dioxide (CO₂) reduction (eCO₂R) over Cu-based bimetallic catalysts is a promising technique for converting CO₂ into value-added multi-carbon products, such as fuels, chemicals, and materials. For improving the process efficiency, electrocatalyst development for the eCO₂R must be integrated with tuning of operating conditions. For example, CuIn-based materials typically lead to preferential C₁ product selectivity, which delivers the desired C₂₊ products upon varying the In/Cu ratio and operating conditions (i.e., in 0.1 M KHCO₃ electrolytes using an H-type cell with a cation exchange membrane vs. in 1 M KOH electrolytes using a flow cell with an anion exchange membrane). At lower Cu-loading (i.e., InCu₅O_x material), the maximum faradaic efficiency of HCOOH (FE_HCOOH) of 70% was achieved at −1 V versus the reversible hydrogen electrode (vs. RHE) in an H-type cell. However, upon increasing the Cu loading, the preferential product selectivity could be altered: the InCu₇₃O_x material led to a high CO selectivity (maximum FE of 51%) in the H-type cell at −0.8 V vs. RHE and delivered a current density of 100 mA cm⁻² with a FE_C2+ of up to 37% at −0.8 V vs. RHE in the flow cell configuration. Various characterization tools were also employed to probe the catalytic materials to rationalize the electrocatalytic performance.