Electrolytic upcycling of PET waste plastics for energy-efficient hydrogen evolution

Abstract

Electrocatalytic reforming of polyethylene terephthalate (PET) is a sustainable way to treat plastic waste. However, most of the electrocatalysts are only active for PET hydrolyzed product (ethylene glycol, EG) oxidation, not for PET decomposition. Herein, we present a PET decomposition and electrolytic upcycling route catalyzed by a molybdic polyoxometalate (H₃PMo₁₂O₄₀, PMo₁₂) mixed acid system, which can convert waste PET into terephthalic acid (TPA) and hydrogen fuel. PMo₁₂ is an efficient PET hydrolysis catalyst even under mild conditions (<100 °C, 1 atm, and low acid concentration <2.5 mol L⁻¹). It simultaneously oxidizes the hydrolyzed product, EG, to formic acid (FA), promoting continuous PET hydrolysis and leading to a near-complete conversion of PET (∼100%). The PMo₁₂ catalyst also acts as an electro-carrier recycled through a coupled electrolysis process. H₂ is produced with a low energy consumption of 2.09 kW h N m⁻³, which is only 50.6% of the energy required for water electrolysis. Aspen modeling and Life Cycle Assessment (LCA) analysis show great industrial potential and a reduced carbon footprint of the PET electrolytic upcycling route.