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 FeCo3NiCu0.5Zr HEA catalyst by precisely designing the metal composition and adjusting the metal ratio. 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 of furfuryl alcohol remained above 90% with furfural conversion exceeded 99%. H2-TPR and H2O-TPD characterizations results revealed that the HEA nanoparticles not only possessed excellent hydrothermal stability but also dissociated surface free water molecules to generate H* and *OH. Further, the surface oxygen vacancies are generated through the combination of bridging hydroxyl and terminal hydroxyl groups on the HEA surface, accompanied by releasing of H2O. The carbonyl group of furfural molecule preferentially adsorbs on the 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 to high value-added chemicals in the presence of water.Green foundation1.This work realizes the highly efficient conversion of furfural in the presence of water by delicately designing HEAs. It not only broadens the application range of abundant transition metals in catalysis, but also helps to improve the utilization efficiency of biomass resources and reduce the generation of waste. 2. The designed hydrothermally stable high-entropy catalyst achieved near-complete conversion of furfural with up to 98% selectivity toward the target product furfuryl alcohol in the presence of 8% water. Moreover, the catalyst can maintain high conversion and high selectivity after five consecutive cycles. 3. Future work will focus on finding simpler and more efficient methods to achieve large-scale preparation of high-entropy catalysts for efficient conversion of biomass or biomass platform molecules in the presence of water.