Electrochemical PET recycling to formate through ethylene glycol oxidation on Ni–Co–S nanosheet arrays

Abstract

Plastics have become an integral part of modern society due to their excellent mechanical properties, light weight, chemical stability and low cost. However, their continuous production and use worldwide have resulted in a major environmental problem. In this context, the green degradation and upcycling of waste plastics using electrochemical oxidation present a promising solution. To make this solution practical, the development of cost-effective catalysts optimized for this reaction is essential. In this study, we propose a new catalyst for the electrocatalytic reforming of ethylene glycol (EG) derived from polyethylene terephthalate (PET) to formic acid. The catalyst comprises layered Ni–Co₉S₈ nanosheet arrays (NSAs) grown on nickel foam (NF) via the hydrothermal method. Under EG oxidation reaction (EGOR) conditions, the Ni–Co₉S₈ NSAs/NF catalyst achieves Faraday efficiencies (FEs) of up to 92%. Additionally, the direct use of commercial PET plastic powder hydrolysate still enables formate FEs to exceed 90%. These outstanding results are rationalized using density functional theory (DFT) calculations providing insights into the role of the different elements in the EGOR. Overall, this study demonstrates both a synthetic strategy for transition metal sulfides and an efficient and sustainable strategy for the upgraded recycling of PET plastics.