K–FeCu/Multiwalled Carbon Nanotube with Hydrophobic Confinement and Multisites Synergy for Boosting CO ₂ Hydrogenation to Ethanol

CO₂ hydrogenation to ethanol is a promising pathway for carbon utilization, yet it remains challenged by the deactivation of iron-based catalysts due to water byproducts and the difficulty in controlling product selectivity. To address these issues, this work constructed hydrophobic MWCNT-supported K-FeCu bimetallic catalysts and systematically investigated their structure-activity relationships. The optimized catalyst (Fe/Cu = 0.5) exhibited superior performance at 320 °C and 4 MPa, achieving a CO₂ conversion of 41.1%, with ethanol selectivity and space-time yield (STY) reaching 28.91% and 175.91 mg·gcat⁻¹·h⁻¹, respectively. Mechanistic studies revealed that the intrinsic hydrophobicity of MWCNT facilitated water desorption to preserve the active Fe₅C₂ phase. Synergistically, Cu promoted Fe reduction via hydrogen spillover, while K inhibited excessive hydrogenation, facilitating the C-C coupling of RWGS-derived CHxO* and CHx* intermediates at the interface. This study highlighted the importance of hydrophobic surface engineering, providing a strategy for designing catalysts for CO₂ hydrogenation to ethanol.