Concentration-Dependent Photocatalytic Upcycling of Poly(ethylene terephthalate) Plastic Waste

Hongxing Kang; Audrey Washington; Matt D Capobianco; Xingxu Yan; Vayle Vera Cruz; Melanie Weed; Jackie Johnson; Gonto Johns 3rd; Gary W Brudvig; Xiaoqing Pan; Jing Gu

doi:10.1021/acsmaterialslett.3c01134

Concentration-Dependent Photocatalytic Upcycling of Poly(ethylene terephthalate) Plastic Waste

ACS Mater Lett. 2023 Oct 16;5(11):3032-3041. doi: 10.1021/acsmaterialslett.3c01134. eCollection 2023 Nov 6.

Authors

Affiliations

¹ Department of Chemistry and Biochemistry, San Diego State University, 5500 Campanile Drive, San Diego, California 92182, United States.
² Department of Chemistry and Yale Energy Sciences Institute, Yale University, New Haven, Connecticut 06520-8107, United States.
³ Department of Materials Science and Engineering, University of California, Irvine, Irvine, California 92697, United States.
⁴ Department of Physics and Astronomy, University of California, Irvine, Irvine, California 92697, United States.

Abstract

Photocatalytic plastic waste upcycling into value-added feedstock is a promising way to mitigate the environmental issues caused by the nondegradable nature of plastic waste. Here, we developed a MoS₂/g-C₃N₄ photocatalyst that can efficiently upcycle poly(ethylene terephthalate) (PET) into valuable organic chemicals. Interestingly, the conversion mechanism is concentration-dependent. For instance, at a low ethylene glycol (EG) concentration (7.96 mM), acetate is the main product. Unexpectedly, the conversion of PET water bottle hydrolysate with only 7.96 mM ethylene glycol (EG) can produce a 4 times higher amount of acetate (704.59 nmol) than the conversion of 300 mM EG (174.50 nmol), while at a higher EG concentration (300 mM), formate is the dominant product. Herein, a 40 times higher EG concentration (300 mM compared to 7.96 mM) would produce only ∼3 times more formate (179 nmol compared to 51.86 nmol). In addition, under natural sunlight conditions, comparable amounts of liquid and gaseous products are produced when commercial PET plastics are employed. Overall, the photocatalytic PET conversion process is quite efficient under a low concentration of EG in PET hydrolysate, indicating the enormous potential of this photocatalysis strategy for real plastics upcycling.