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.