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.