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 CO2 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 CO2 wastes into value-added formic acid (HCOOH), in which both the anode (oxygen-vacancy-rich Ni(OH)2-VO) and cathode (Bi/Bi2O3 heterostructure) electrocatalysts were elaborately designed from PET derivatives. Impressively, the as-prepared Ni(OH)2-VO and Bi/Bi2O3 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 Ni3+ species and accelerate the subsequent processes of dehydrogenation and C–C bond breakage during PET upcycling. Meanwhile, the interface electron transfer from Bi2O3 to Bi benefits the keeping of high valence of Bi sites and optimizes the adsorption of OCHO* intermediate, thereby endowing Bi/Bi2O3 with efficient performance toward CO2 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.