Nickel-based catalysts for hydrogen production from plastic waste: recent advances, challenges, and future perspectives

Plastic-to-hydrogen conversion offers a route to combine waste-plastic valorization with low-carbon hydrogen production, but progress remains constrained by catalyst deactivation under heterogeneous feedstocks and by limited scale-up evidence. This review provides a Ni-centered assessment that, unlike broader plastic-to-hydrogen reviews, explicitly links catalyst composition and structure with reaction pathways, deactivation, regeneration, reactor operation, and techno-economic and life-cycle performance. Ni catalysts based on Al 2 O 3 , MgO, CeO 2 , ZrO 2 , mixed oxides, promoters, and bimetallic formulations are critically compared across pyrolysis–steam reforming, catalytic pyrolysis, and gasification. Reported hydrogen yields are interpreted in relation to Ni dispersion, support acidity/basicity, redox behavior, steam availability, and feedstock chemistry. Coke deposition, Ni sintering, and sulfur/chlorine poisoning emerge as the principal stability limitations, while support engineering, promoter addition, bimetallic design, and site-confined architectures provide complementary mitigation routes. Techno-economic studies show that projected hydrogen costs are highly scenario-dependent, with plant scale, feedstock valuation, syngas/H 2 yield, heat integration, purification, and carbon-management assumptions controlling competitiveness. Life-cycle results are likewise limitation and configuration dependent and do not universally favor plastic-derived H 2 over grey hydrogen. By integrating catalyst-scale evidence with process and system-level assessment, this review clarifies why promising laboratory performance does not yet translate directly into commercial readiness. It identifies long-duration catalyst testing, continuous mixed-plastic operation, standardized reporting, pilot-scale validation, and experimentally grounded AI/ML datasets as the critical requirements for credible industrial translation.