Short-Range Order Stabilized Ultrafine Pd on Carbon-Supported Medium-Entropy Mesoporous Interfaces for Plastic Upcycling

Abstract Maximizing atomic utilization of noble metals is essential for high-efficiency electrocatalysis. However, small-sized noble metal nanoparticles (NPs) often struggle to achieve both high activity and structural stability. Here, we demonstrate that ultrafine Pd NPs (sub-3 nm) can be stabilized at a carbon-supported, short-range-ordered FeCoNiB mesoporous matrix. Through precise control of the Ni/Co ratio of FeCoNiB and Pd loading, the resulting material features a well-defined mesoporous architecture with abundant crystalline–amorphous interfaces. The optimized Pd4.4-FeCoNiB electrode with 4.4 at. % Pd loading shows a high mass activity (3.41 A mgPd–1), a Faradaic efficiency up to 98.81%, and durability toward electrocatalytic conversion of waste polyethylene terephthalate-derived ethylene glycol (EG) into value-added glycolic acid (GA). These improvements stem from strong electronic and interfacial coupling between FeCoNiB and Pd, which is further stabilized by short-range ordering in the amorphous alloy. Such interactions not only enhance the structural integrity of Pd active sites but also facilitate EG activation and GA desorption. This work highlights a promising interfacial design route for developing cost-effective and durable low Pd-loading electrocatalysts for plastic upcycling.