From poison to promoter: high-entropy alloy-enabled water activation for robust furfural hydrogenation in a water-containing system

Abstract

High-entropy alloys (HEAs), as new catalytic materials, reveal excellent catalytic performance in numerous reactions. However, how to rationally design high-entropy alloy catalysts with high hydrothermal stability for the efficient hydrogenation of biomass in the presence of water remains a challenge. In this work, we successfully synthesized an FeCo₃NiCu_0.5Zr HEA catalyst by precisely designing the metal composition and adjusting the metal ratios. The catalyst achieved near-complete conversion (>99%) of furfural with up to 98% selectivity toward the target product, furfuryl alcohol, in the presence of 8% water. Even if the water content increased to 20%, the selectivity for furfuryl alcohol remained above 90%, with furfural conversion exceeding 99%. H₂-TPR and H₂O-TPD characterization results revealed that the HEA nanoparticles not only possessed excellent hydrothermal stability but also dissociated surface free water molecules to generate H* and *OH. Furthermore, the surface oxygen vacancies are generated through the combination of bridging hydroxyl and terminal hydroxyl groups on the HEA surface, accompanied by the release of H₂O. The carbonyl group of the furfural molecule preferentially adsorbs on a surface oxygen vacancy in the catalyst, which effectively shortens the distance between the active hydrogen and the carbonyl group, thereby promoting the hydrogenation reaction. This study not only broadens the application of high-entropy metal compounds but also promotes the directional conversion of biomass into high-value-added chemicals in the presence of water.