Trash to treasure: electrocatalytic upcycling of polyethylene terephthalate (PET) microplastic to value-added products by Mn_0.1Ni_0.9Co₂O_4-δ RSFs spinel

Microplastic pollution has emerged as a pressing environmental issue of global concern due to its detrimental effects on the environment and ecology. Restricted to their characters of complex composition, it is a great challenge to propose a more cost-effective approach to achieve highly selective conversion of microplastic into add-value products. Here we demonstrate an upcycling strategy for converting PET microplastics into added-value chemicals (formate, terephthalic acid and K₂SO₄). PET is initially hydrolyzed in KOH solution to produce terephthalic acid and ethylene glycol, which is subsequently used as an electrolyte to produce formate at the anode. Meanwhile, the cathode undergoes hydrogen evolution reaction to produce H₂. Preliminary techno-economic analysis suggests that this strategy has certain economic feasibility and a novel Mn_0.1Ni_0.9Co₂O_4-δ rod-shaped fiber (RSFs) catalyst we synthesized can achieve high Faradaic efficiency (> 95%) at 1.42 V vs. RHE with optimistic formate productivity. The high catalytic performance can be attributed to the doping of Mn changing the electronic structure and reducing the metal-oxygen covalency of NiCo₂O₄, reducing the lattice oxygen oxidation in spinel oxide OER electrocatalysts. This work not only put forward an electrocatalytic strategy for PET microplastic upcycling but also guides the design of electrocatalysts with excellent performance. © 2023 Elsevier B.V.