K–FeCu/Multiwalled Carbon Nanotube with Hydrophobic Confinement and Multisites Synergy for Boosting CO2 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.