A novel high-entropy spinel ferrites (CoNiCuZnMg)Fe₂O₄ catalyst for H₂ production via steam reforming of derived volatiles from polypropylene and waste cooking oil

Municipal organic waste conversion to high-value products is a vital carbon–neutral way to simultaneously tackle the energy crisis and environmental contamination. This study aims to develop and evaluate a novel high-entropy spinel ferrites (Co_0.2Ni_0.2Cu_0.2Zn_0.2Mg_0.2)Fe₂O₄ catalyst (HEO) toward H₂ production from co-pyrolysis volatiles of polypropylene (PP) and waste cooking oil (WCO) in an integrated two-stage reactor system. In the 1st stage of medium temperature reforming, the optimal 3:7 PP/WCO blend mass ratio facilitated H₂ production. Under a catalytic reforming at high temperature of 750 °C in the 2nd stage, the HEO catalyst demonstrated remarkable efficiency, yielding 58.43 mmol·g⁻¹ of H₂ with a composition of 65.17 %, a notable 22.3 times higher than that without HEO. The catalyst exhibited a prolonged service life of 540 min without compromising H₂ selectivity, maintaining a high yield of 510.2 mmol·g_cat.⁻¹·s⁻¹. The exceptional performance of HEO arises from the synergistic effects of multiple elements, augments oxygen vacancy, enhances reducibility, and promotes structural stability in the high-entropy system, which causes the strong C–C breaking ability and the excellent C–H breaking abilities of Fe, Ni, Co, Cu, and Zn species. The analysis of tar, gaseous products, and deactivated HEO catalyst characterization results provides a comprehensive understanding of the co-pyrolysis route and volatiles catalytic reforming process. This study developed a high-entropy ferrite catalyst that not only achieves efficient and stable H₂ production but also lays the foundation for a new high-entropy catalyst design concept, fostering the development of efficient reforming catalysts for H₂ production.