Magnetically recoverable high-entropy alloy catalyst in carbon matrix for ammonia borane-driven hydrogen evolution and electrocatalytic hydrogen production

Abstract

Designing multimodal catalysts with high efficiency and durability remains a central challenge in clean energy research. High-entropy materials, composed of multiple principal elements, have recently emerged as promising candidate in catalysis owing to their tunable active sites, synergistic effects, and enhanced stability. In this study, a novel non-noble metals based high entropy metal–organic framework (HE-MOF) was synthesized and subsequently converted into a high-entropy alloy in carbon matrix (HEA@Carbon) through controlled thermal treatment under static hydrogen atmosphere. Detailed structural and compositional analyses were carried out using XRD, FTIR, Raman, SEM-EDX, and TEM to confirm the successful formation of the HEA phase with the preservation of the carbon morphology. The HEA@Carbon catalyst exhibited excellent catalytic performance for the hydrolysis of ammonia borane (AB), achieving a TOF value of 316 min⁻¹ with an apparent activation energy (E_a) of 9.6 kJ mol⁻¹, representing a nearly tenfold decrease in activation energy for AB hydrolysis compared to the non-catalytic reaction. The catalyst retained nearly identical catalytic activity over five consecutive cycles, demonstrating excellent durability. Importantly, the HEA@Carbon catalyst's inherent magnetic recoverability enables facile separation and reuse, with 96% catalyst recovery after the reusability test, underscoring its practical suitability for scalable hydrogen production. Beyond catalytic hydrogen production from chemical hydrides, HEA@Carbon exhibited notable electrocatalytic hydrogen evolution reaction (HER) activity with an overpotential of 400 mV at 10 mA cm⁻² and a Tafel slope of 92 mV dec⁻¹, together with the long-term operational stability. These results underscore the great potential of HEA embedded within a carbon matrix as a bifunctional catalyst for both chemical and electrochemical hydrogen generation, for next-generation hydrogen energy systems.