Trash to treasure: electrocatalytic upcycling of polyethylene terephthalate (PET) microplastic to value-added products by Mn0.1Ni0.9Co2O4-δ RSFs spinel

Chemical catalytic upgrading of polyethylene terephthalate plastic waste into value-added materials, fuels and chemicals

The substantial production of polyethylene terephthalate (PET) products, coupled with high abandonment rates, results in significant environmental pollution and resource wastage. This has prompted global attention to the development of rational strategies for PET waste treatment. In the context of renewability and sustainability, catalytic chemical technology provides an effective means to recycle and upcycle PET waste into valuable resources. In this review, we initially provide an overview of strategies employed in the thermocatalytic process to recycle PET waste into valuable carbon materials, fuels and typical refined chemicals. The effect of catalysts on the quality and quantity of specific products is highlighted. Next, we introduce the development of renewable-energy-driven electrocatalytic and photocatalytic systems for sustainable PET waste upcycling, focusing on rational catalysts, innovative catalytic system design, and corresponding underlying catalytic mechanisms. Moreover, we discuss advantages and disadvantages of three chemical catalytic strategies. Finally, existing limitations and outlook toward controllable selectivity and yield enhancement of value-added products and PET upvaluing technology for scale-up applications are proposed. This review aims to inspire the exploration of waste-to-treasure technologies for renewable-energy-driven waste management toward a circular economy.

Concurrent electrocatalytic hydrogen evolution and polyethylene terephthalate plastics reforming by self-supported amorphous cobalt iron phosphide electrode

The electrocatalytic hydrogen evolution reaction (HER) coupled with oxidative transformation of plastics into commodity chemical is a promising tactic to relieve the energy shortage and white pollution problems via sustainable and profitable manner, which necessitates highly active bifunctional catalytic electrode and meticulous construction of electrolysis system. Herein, a self-supported amorphous cobalt iron phosphide onto nickel foam (NF) substrate, labeled as CoFe-P/NF, was prepared by electrodeposition, which served as bifunctional catalytic electrode for alkali hydrogen evolution reaction (HER) and selective electrooxidation of polyethylene terephthalate (PET) plastic hydrolysate toward formate. Benefiting from the abundant catalytic sites within amorphous structure, the interelement synergy and sufficient exposure of catalyst to electrolyte, the self-supported CoFe-P/NF electrode displayed low overpotential (η100 of 168 mV at current density of J = 100 mA cm-2), decent stability for HER and fine tolerance to PET monomers. The CoFe-P/NF electrode could also catalyze selective electrooxidation of ethylene glycol (EG) component in PET hydrolysate to formate with high productivity (0.1 mmol cm-2h-1) and faradaic efficiency (FE, 90 %) at 1.5 V. The PET hydrolysate electrolysis system based on CoFe-P/NF enabled coproduction of H2 and value added formate at lower voltage (1.52 V at J = 20 mA cm-2) and energy consumption (84 % at J = 200 mA cm-2) relative to water electrolysis. This work showcases the coproduction of H2 fuel and formate by electrolysis of PET hydrolysate via rational design of bifunctional catalytic electrode. We believe such type of versatile catalytic electrodes can find application scenarios in electrosynthesis of more commodity chemicals and energy devices beyond the case herein.