Innovative routes for hydrogen production from waste plastics: a comprehensive review of thermochemical, photocatalytic, and electrocatalytic technologies

Abstract

The transformation of waste plastics into hydrogen is a field that embodies both pressing challenges and promising opportunities when considered from economic, technological, and societal viewpoints. The review outlines a critical evaluation of recent developments and innovative strategies that integrate plastic waste recycling with hydrogen production. Major technological routes include pyrolysis, gasification, aqueous-phase reforming, photoreforming, and electrocatalytic conversion. Among these approaches, pyrolysis and gasification have emerged as the most mature and industrially scalable options, especially when coupled with catalytic reforming or the water–gas shift reaction to enhance hydrogen yield. Pyrolysis involves the thermal decomposition of plastics in an oxygen-free environment, whereas gasification employs steam or controlled oxidants to generate syngas; in both cases, however, the processes are energy-intensive and require careful optimization. Aqueous catalytic reforming, typically carried out under moderate temperatures and pressures, offers particular promise for oxygen-containing plastics due to its selective hydrogen production. Nonetheless, widespread deployment is constrained by high catalyst costs, deactivation phenomena, and the limited availability of suitable feedstocks. By contrast, photoreforming and electrocatalytic methods represent emerging low-carbon alternatives, drawing on solar or electrical energy to directly convert polymeric waste into hydrogen. Despite their sustainability advantages, these techniques currently face barriers such as low reaction efficiency, restricted applicability to specific polymer classes (notably oxygenated plastics), and difficulties in scaling up to continuous industrial systems. In addition to examining laboratory-scale advances, this review also considers global industrial initiatives that demonstrate the feasibility of plastic-to-hydrogen pathways. Key obstacles include optimizing hydrogen selectivity, reducing overall energy consumption, and ensuring stable long-term operation. Overcoming these barriers will be essential for the commercialization of technologies that can simultaneously address plastic pollution and contribute to clean hydrogen economies.