Photothermal catalysis for plastic upcycling: a review on material design and reaction mechanisms

Abstract

The accumulation of non-degradable plastic waste presents a critical environmental challenge, necessitating the development of energy-efficient and sustainable recycling methodologies. Conventional thermal catalytic processes often entail high energy inputs and limited selectivity, while photocatalytic approaches suffer from low quantum yields. Photothermal catalysis has emerged as a synergistic strategy that harnesses broadband solar irradiation to generate localized thermal gradients and active charge carriers, thereby enabling efficient the chemical upcycling of polymeric substrates under mild operational conditions. This review comprehensively examines recent advances in photothermal catalysis for plastic valorization, with emphasis on mechanistic understanding, photo-thermal material classification, and structural design principles. Plasmonic metals (e.g., Au, Ag, Ru), defective semiconductors (e.g., oxygen-deficient TiO₂, doped g-C₃N₄), and carbon-based nanostructures (e.g., graphene, carbon nanotubes) are analyzed in terms of their light-to-heat conversion efficiency and catalytic functionality. We further summarize engineering strategies for enhanced photon utilization and reaction kinetic, including defect modulation and heterojunction formation, evaluate critical aspects from reactor design to scalability, address key challenges of stability and feasibility, and propose future directions such as machine learning-assisted catalyst discovery. This work aims to provide a foundational framework for the development of solar-driven plastic upcycling technologies aligned with circular economy objectives.

Keywords

photothermal catalysis / plastic upcycling / plasmonic materials / semiconductor catalysts / chemical recycling

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