State-of-the-art and perspectives of hydrogen generation from waste plastics

Waste plastic utilization and hydrogen production present significant economic and social challenges but also offer opportunities for research and innovation. This review provides a comprehensive analysis of the latest advancements and innovations in hydrogen generation coupled with waste plastic recycling. It explores various strategies, including pyrolysis, gasification, aqueous phase reforming, photoreforming, and electrocatalysis. Pyrolysis and gasification in combination with catalytic reforming or water gas-shift are currently the most feasible and scalable technologies for hydrogen generation from waste plastics, with pyrolysis operating in an oxygen-free environment and gasification in the presence of steam, though both require high energy inputs. Aqueous phase reforming operates at moderate temperatures and pressures, making it suitable for oxygenated plastics, but it faces challenges related to feedstock limitations, catalyst costs and deactivation. Photoreforming and electrocatalytic reforming are emerging, sustainable methods that use sunlight and electricity, respectively, to convert plastics into hydrogen. Still, they suffer from low efficiency, scalability issues, and limitations to specific plastic types like oxygenated polymers. The challenges and solutions to commercializing plastic-to-hydrogen technologies, drawing on global industrial case studies have been outlined. Maximizing hydrogen productivity and selectivity, minimizing energy consumption, and ensuring stable operation and scaleup of plastic recycling are crucial parameters for achieving commercial viability.