Hydrogen production from waste plastics: Sustainable processes, recent advances, and emerging trends

Plastic waste valorization into hydrogen has attracted increasing attention as a dual solution for mitigating plastic pollution and supplying clean energy. This review provides a comprehensive overview of recent advances in plastic-to-hydrogen technologies, with emphasis on both established and emerging approaches. Thermochemical routes, including supercritical water gasification, are critically assessed alongside catalytic pathways such as catalytic supercritical water gasification (SCWG), catalytic pyrolysis, and combined pyrolysis–gasification systems. In addition, novel strategies—including microwave-assisted deconstruction, photoreforming, and electrocatalytic upcycling—are examined, together with hybrid approaches that integrate the strengths of multiple methods. Special focus is given to mechanistic insights, the role of operating conditions in hydrogen selectivity, the challenges of catalyst design, deactivation, and regeneration, as well as techno-economic analysis and life cycle assessment. By comparing the advantages and limitations of different routes, this review identifies critical research gaps and highlights future opportunities for scaling up plastic-to-hydrogen conversion. Ultimately, the paper aims to guide the development of efficient, sustainable processes that contribute to circular economy goals and the transition to a carbon-neutral energy system. • Comprehensive review of thermochemical, catalytic, and emerging routes for hydrogen production from waste plastics. • Critical assessment of supercritical water gasification, catalytic pyrolysis, and integrated pyrolysis–gasification systems. • Mechanistic insights into hydrogen selectivity, operating parameters, and catalyst design, deactivation, and regeneration. • Evaluation of emerging technologies including microwave-assisted conversion, photoreforming, and electrocatalytic upcycling. • Integrated TEA–LCA: cost, energy, and environmental trade-offs. • Identification of research gaps and scale-up challenges to advance sustainable plastic-to-hydrogen conversion within a circular economy framework.