CuO-Nanoparticles Decorated in g-C₃N₄/MXene Architecture for Efficient Electrochemical CO₂ Reduction to Ethylene

Electrochemical reduction of CO₂ into multi-carbon products provides a sustainable pathway for carbon utilization and value-added chemical production. Herein, CuO nanoparticles are integrated within two-dimensional sandwich heterostructures of graphitic carbon nitride (g-C₃N₄) and MXene (Ti₃C₂T_x) via sequential spray-coating (SP) to form g-C₃N₄–CuO@MXene(SP) and MXene–CuO@g-C₃N₄(SP). Structural analyses reveal highly dispersed CuO nanoparticles (~ 8 nm) that are strongly anchored to nitrogen sites in g-C₃N₄ and stabilized by the MXene overlayer, which suppresses aggregation and enhances electrical conductivity. The excellent activity and C–C coupling for ethylene production are facilitated by the strong anchoring of CuO on the extended surfaces of Ti₃C₂T_x and g-C₃N₄, resulting in a large number of exposed active sites that promote effective conversion and operational stability. X-ray photoelectron spectroscopy confirms the coexistence of Cu⁰ and Cu⁺ species, which play complementary roles in CO adsorption and C–C coupling. Electrochemical evaluation shows that both sandwich catalysts outperformed the binary (MXene–CuO and g-C₃N₄–CuO) and sonicated ternary composites. Notably, g-C₃N₄–CuO@MXene(SP) exhibits the highest performance, delivering a Faradaic efficiency of ~ 87% for C₂H₄ at − 0.84 V vs. RHE, in a flow cell system. These findings establish g-C₃N₄–CuO@MXene(SP) as a robust and selective electrocatalyst for CO₂-to-ethylene conversion, offering a promising route toward sustainable chemical manufacturing and carbon management.