Electrocatalytic Reduction of CO₂ to Long-Chain Hydrocarbons on (FeCoNiCu)₃O₄ Medium Entropy Oxide Nanoparticles

Electrocatalytic CO2 reduction reaction (CO2RR) to valuable multicarbon (C2+) fuels and chemicals presents a promising strategy to mitigate atmospheric CO2 accumulation and promote the closure of the carbon cycle. However, significant challenges persist in achieving both high product selectivity and sustained stability in the CO2RR. In this study, the catalytic performance of (Fe,Co,Ni,Cu)3O4 medium entropy oxide (MEO) nanoparticles anchored on reduced graphene oxide (rGO) was evaluated for the CO2RR. The MEO-rGO catalyst exhibited remarkable activity, achieving a cathodic current density of -0.5 A cm-2 at -1.7 V, significantly outperforming bare nickel foam (-0.15 A cm-2). Additionally, the catalyst demonstrated a high total Faradaic efficiency (FE) of 60.3% for C2+ products, comprising 30.6% C5H12O and 29.7% C5H10O. This exceptional selectivity toward long-chain hydrocarbons is attributed to the enhanced C-C coupling on the MEO-rGO surface, facilitated by reduced energy barriers. Density functional theory (DFT) calculations further revealed that the adsorption and reduction of CO2 on the (Fe,Co,Ni,Cu)3O4 MEO surface are energetically favorable processes.