Electrocatalytic Waste-Treating-Waste Strategy for Concurrently Upgrading of Polyethylene Terephthalate Plastic and CO₂ into Value-Added Formic Acid

Abstract

Polyethylene terephthalate (PET) plastic and CO 2 pollution have seriously threatened the ecological environment and caused a huge waste of carbon resources. Herein, we report an electrocatalytic waste-treating-waste strategy for concurrently upgrading PET plastic and CO 2 wastes into value-added formic acid (HCOOH), in which both the anode (oxygen-vacancy-rich Ni(OH) 2 -V O ) and cathode (Bi/Bi 2 O 3 heterostructure) electrocatalysts were elaborately designed from PET derivatives. Impressively, the as-prepared Ni(OH) 2 -V O and Bi/Bi 2 O 3 achieve high selectivity of HCOOH (86 and 91%, respectively) with industrial-level current densities at ultralow potentials (300 mA cm −2 at 1.6 V and −272 mA cm −2 at −1.4 V, respectively). Further experimental and theoretical results reveal that the abundant oxygen vacancies will largely facilitate the formation of Ni 3+ species and accelerate the subsequent processes of dehydrogenation and C−C bond breakage during PET upcycling. Meanwhile, the interface electron transfer from Bi 2 O 3 to Bi benefits the keeping of high valence of Bi sites and optimizes the adsorption of OCHO* intermediate, thereby endowing Bi/Bi 2 O 3 with efficient performance toward CO 2 reduction to HCOOH. As a proof of concept, a solar-powered flow reactor with real-time monitoring and control functions was designed, which realized a record Faradaic efficiency of 181% for HCOOH. This work offers opportunities for waste utilization and provides constructive guidance for the design of advanced electrocatalysts for converting wastes into valuable chemicals.

Upcycling of Plastic Waste Using Photo-, Electro-, and Photoelectrocatalytic Approaches: A Way toward Circular Economy

“…Therefore, when the same analysis was carried out with the current density of 300 mA cm –2 , the process becomes profitable and approximately a profit of USD 355 per ton PET upcycled is achieved . An excellent strategy to increase the selectivity, FE, conversion, and profit of this process is to substitute H 2 evolution cathodic reaction to another reaction like CO 2 reduction to yield the same product HCOOH in both electrodes. , This strategy eliminates the complexities in this system and the TEA of this system shows an increase in the overall profit from USD 355 per ton to USD 550 per ton PET upcycled . In conclusion, the conversion of EG to formic acid or formate can be made economically viable and profitable with high operating current density or by replacing the H 2 evolution reaction with reactions like CO 2 reduction to achieve the same product at both the electrodes.…”