Review on the Pivotal Role of Interfacial Sites in Multicomponent Catalysts for Promoting Selective CO_x Hydrogenation to Ethanol

With growing emphasis on circular carbon economy, catalytic CO_x (CO/CO₂) conversion offers a sustainable route for ethanol synthesis, yet challenges persist in achieving high selectivity due to competing single-carbon products formation (e.g., CO, methane, and methanol formation). Multicomponent catalysts, which consist of two or more distinct metal species with cooperative synergistic interactions between discrete active sites, exhibit high ethanol selectivity in CO_x hydrogenation reactions. Here, this review comments on the critical role of interfacial sites, where metal–metal or metal–oxide interactions modulate electronic and geometric properties, in multicomponent bifunctional catalysts for selective CO_x hydrogenation to ethanol. We first highlight how engineered metal–oxide interfaces and nanoscale metal intimacy (e.g., in Rh-, Cu-, Co-, and in-based multicomponent bifunctional catalysts) synergistically activate CO_x, stabilize key intermediates (e.g., CH_x*, CO*, and CH_xO*), and thereby promoting C─C coupling. Advanced strategies, including atomic layer deposition (ALD), surface organometallic chemistry (SOMC), and strong electrostatic adsorption (SEA), for engineering interfacial sites are then discussed. The mechanistic insights (obtained from advanced characterization) into these catalytic systems are then discussed, followed by the proposed future research avenues for the field. This review serves as the roadmap for developing efficient catalysts to advance CO_x-to-ethanol technology.