Unlocking C3–4 products in CO electroreduction via one-step square-ring coupling on Cu4-embedded carbon nitride

Abstract

The electrochemical conversion of CO₂ and CO into value-added multi-carbon compounds through sustainable pathways presents a promising strategy for achieving carbon neutrality. Although significant advancements have been achieved in the electrocatalytic reduction of C_1–2 products, such as methane (CH₄) and ethylene (C₂H₄), the selective and efficient production of C_3–4 compounds remains a formidable challenge. This is primarily due to the intricate nature of carbon–carbon coupling mechanisms and the complex dynamics of proton-coupled electron transfer (PCET). In this study, we employed density functional theory (DFT) calculations to systematically investigate the feasibility of C_3–4 product formation on a copper-embedded carbon nitride (Cu₄–C₅N₂H₂). Two distinct pathways for C₃ coupling formation have been identified: trimerization of C–C–C through the CO trimerization coupling mechanism and 3CO-ER coupling mechanism. Propylene emerged as the preferred C₃ product, with a low limiting potential (U_L) of −0.55 V. For the generation of C₄ products, we have proposed an unprecedented one-step square-ring coupling mechanism and a 4CO-ER coupling mechanism, with n-butanol as the predominant product, and we also discuss the potential generation of cyclobutane, n-butene and 1,3-butadiene. This work provides new insights into multi-carbon coupling mechanisms and offers a viable strategy for the development of efficient electrocatalysts for CO reduction to C_3–4 products.