Co-Electrolysis of PET and CO2 using a Co-MOF-74-Derived Anode and a Polymeric Co-Phthalocyanine Cathode

Mitigating carbon emissions and plastic waste is a pressing societal challenge due to the disruptive environmental impact of incremental accumulation. A promising strategy to address both issues involves the development of coupled electrolysers that can utilise CO2 and PET-plastic waste as resources for electricity-driven manufacturing of high-value commodity chemicals. Here, we report electrocatalytic upcycling of polyethylene terephthalate (PET) plastic to formate and terephthalic acid using a cobalt-based metal-organic framework (Co-MOF-74). The electrocatalyst undergoes oxidative restructuring to cobalt oxyhydroxide (CoOOH) under operating conditions which is demonstrated using ex situ and in situ measurements. The MOF-derived electrocatalyst exhibited near-unity faradaic efficiency (FE) for oxidation of ethylene glycol to formate during short-term electrolysis and lowered the required potential by 0.23 V compared to the conventional oxygen evolution reaction (OER) at a current density of 100 mA cm–2. When coupled with a CO2R electrode containing a polymeric cobalt-phthalocyanine catalyst in a two-electrode configuration, a maximum combined FE of 156% was achieved for formate (anode) and syngas (cathode) at a cell voltage of 1.6 V. Upon integration of the EGOR electrode in a CO2-fed flow cell, the coupled system required a cell voltage of ~2.3 V to operate at 75 mA cm−2 current density. This work presents a promising integrated approach that offers a compelling solution for mitigating environmental pollution by enabling the electrochemical reforming of CO2 and plastic waste into valuable chemicals under cost-effective and energy-efficient conditions.