Interfacial Insights into the Efficient Electroconversion of CO2 to CO Using Cu-Based Catalysts Supported on Printex L6 Carbon

Abstract

Carbon dioxide (CO2) from fossil fuel combustion drives anthropogenic climate change, and electrochemical CO2 reduction reaction (CO2RR) offers a pathway to convert this waste into valuable chemicals. However, catalytic performance is often discussed in terms of active site density alone, while the role of the local interfacial environment remains insufficiently resolved. Here, a series of Printex L6 carbon-supported copper catalysts (PL6C@Cux, where x corresponds to the actual Cu loading wt %) were systematically evaluated for the selective CO2-to-CO conversion. Through linear sweep voltammetry analysis, PL6C@Cu1.04 was identified as the best-performing catalyst among the catalysts investigated; this catalyst exhibited a marked anodic shift in onset potential (to −0.53 V vs RHE) compared to the bare PL6C and nonoptimized loadings. Rotating ring-disk electrode measurements confirmed CO as the dominant product, detected via oxidation at ∼0.8 V vs RHE. To elucidate the mechanistic origins of the enhancement in catalytic efficiency, the interfacial microenvironment was investigated using a quinone redox probe sensitive to local CO2 concentration and adsorption dynamics. The optimized PL6C@Cu1.04 catalyst showed an estimated 15-fold increase in the local CO2 affinity index compared to the bare PL6C catalyst, associated with a 140 mV positive shift in the half-wave potential of the redox probe. This study offers experimental evidence suggesting that optimizing metal loading not only maximizes active sites but also assists in engineering a CO2-enriched microenvironment, which appears crucial for driving efficient and selective electrocatalysis.