Chemical Upcycling of PET Waste towards Terephthalate Redox Nanoparticles for Energy Storage

Abstract

Over 30 million ton of poly(ethylene terephthalate) (PET) is produced each year and no more than 60% of all PET bottles are reclaimed for recycling due to material property deteriorations during the mechanical recycling process. Herein, a sustainable approach is proposed to produce redox-active nanoparticles via the chemical upcycling of poly(ethylene terephthalate) (PET) waste for application in energy storage. Redox-active nanoparticles of sizes lower than 100 nm were prepared by emulsion polymerization of a methacrylic-terephthalate monomer obtained by a simple methacrylate functionalization of the depolymerization product of PET (i.e., bis-hydroxy(2-ethyl) terephthalate, BHET). The initial cyclic voltammetry results of the depolymerization product of PET used as a model compound show a reversible redox process, when using a 0.1 M tetrabutylammonium hexafluorophosphate/dimethyl sulfoxide electrolyte system, with a standard redox potential of −2.12 V vs. Fc/Fc+. Finally, the cycling performance of terephthalate nanoparticles was investigated using a 0.1 M TBAPF6 solution in acetonitrile as electrolyte in a three-electrode cell. The terephthalate anode electrode displays good cycling stability and performance at high C-rate (i.e., ≥5C), delivering a stable specific discharge capacity of 32.8 mAh.g−1 at a C-rate of 30 C, with a capacity retention of 94% after 100 cycles. However, a large hysteresis between the specific discharge and charge capacities and capacity fading are observed at lower C-rate (i.e., ≤2C), suggesting some irreversibility of redox reactions associated with the terephthalate moiety, in particular related to the oxidation process.

Plastic Waste Valorization by Leveraging Multidisciplinary Catalytic Technologies

“…In addition, various novel polymers with unique properties can be obtained with the depolymerization–repolymerization strategy (Table ). For example, Goujon and co-workers developed a tandem process for upcycling of bis­(2-hydroxyethyl)­terephthalate (BHET), a product of PET glycolysis, by methacrylate functionalization and emulsion polymerization to produce a redox-active terephthalate-based polymer for energy storage . Sardon and co-workers reported upcycling of BPA-PC to value-added aliphatic polycarbonates (APCs) as polymer electrolytes for solid-state batteries and recycled BPA …”

“…For example, Goujon and co-workers developed a tandem process for upcycling of bis(2hydroxyethyl)terephthalate (BHET), a product of PET glycolysis, by methacrylate functionalization and emulsion polymerization to produce a redox-active terephthalate-based polymer for energy storage. 35 Sardon and co-workers reported upcycling of BPA-PC to value-added aliphatic polycarbonates (APCs) as polymer electrolytes for solid-state batteries and recycled BPA. 36 Postfunctionalization provides a viable pathway to increase the functional diversity of existing materials without breaking the polymer skeleton (Figure 3 and Table 1).…”

From plastic waste to new materials for energy storage

“…The recovered BHET was then transformed into an intermediate for the synthesis of redox nanoparticles that show promising performance as anode materials for battery applications. 43…”

“…Recently, some of us proposed a novel chemical upcycling approach to produce redox-active nanoparticles from PET waste for energy storage applications. 43 First, the depolymerisation of PET was performed using a recyclable organocatalyst, resulting in bis(2-hydroxyethyl) terephthalate (BHET) in high yields and purity. (Fig.…”

Mechanistic studies of a lipase unveil a dramatic effect of pH on the selectivity toward the hydrolysis of PET oligomers

“…For instance, heterofunctional terepthalic moieties have shown enormous potential as redox-active materials for energy storage devices. 6 In this context, biocatalysis has irrupted to degrade polymers more selectively into monomers that can be either recycled to the original plastics or upcycled to other building blocks to manufacture products with higher added value. 7 The degradation of poly(ethylene terephthalate) (PET) illustrates how enzyme discovery and engineering have driven the success of biocatalysis on polymer degradation.…”