Entropy-Stabilized Pd/HEO Bifunctional Catalyst for Selective Aqueous-Phase Hydrogenolysis of Cellulose to Ethylene Glycol

Abstract

The selective conversion of cellulose into ethylene glycol (EG) under aqueous conditions is an attractive yet challenging route for sustainable biomass valorization. Herein, a multifunctional Pd/WMoAlNiSiO_x catalyst was developed through a polyvinylpyrrolidone (PVP)-assisted sol-gel strategy, where Pd nanoparticles and PdNi alloy domains were uniformly embedded within an entropy-stabilized high-entropy oxide (HEO) matrix. The high configurational entropy promoted the generation of abundant oxygen vacancies and stabilized Pd-O(H)-M (M = W, Mo, Al, Ni, and Si) interfacial linkages, creating a robust bifunctional interface with cooperative hydrogenation and Lewis acid sites. Under mild hydrothermal conditions (245°C, 4.5 MPa H₂), the catalyst achieved complete cellulose conversion and 68.3% EG selectivity, outperforming conventional Pd/WO₃ systems. Characterization and kinetic studies confirmed that the enhanced performance originated from synergistic interactions between PdNi alloy domains and oxygen-deficient HEO interfaces, which facilitate tandem hydrolysis, retro-aldol cleavage, and hydrogenation. The catalyst also exhibited excellent structural stability and minimal Pd leaching after multiple recycling cycles. This study demonstrates a sustainable catalyst design concept based on entropy-stabilized oxide–metal interfaces, providing a promising approach for efficient biomass conversion in aqueous-phase environments.