Upcycling PET waste into CoNi-based electrocatalysts for ethylene glycol oxidation integrated with energy-efficient...

Plastic waste, particularly polyethylene terephthalate (PET), poses serious environmental challenges due to its accumulation and limited recyclability. Herein, we report a sustainable, closed-loop strategy that simultaneously enables PET waste recovery and energy-efficient hydrogen (H₂) production. PET waste is hydrolysed into terephthalic acid (TPA) and ethylene glycol (EG), which are subsequently repurposed as the organic linker for synthesis of bimetallic CoNi-BDC frameworks on nickel foam (NF) electrodes and as the oxidation substrate, respectively. The optimized CoNi-BDC_1/NF electrode after activation exhibited superior electrocatalytic performance, including low overpotentials of 312, 339, and 363 mV at 50, 100, and 200 mA cm^-2, respectively, for the oxygen evolution reaction (OER), which is employed as a benchmark to optimize catalyst composition. During EG oxidation reaction (EGOR), high Faradaic efficiencies (FEs) towards formate are maintained across a broad range of cell voltages, while FEs towards oxalate remain low. The FEs towards formate shows slight variation over repeated operation cycles. Mechanistic studies reveal that CoNi-BDC_1/NF functions as a pre-electrocatalyst and undergoes in situ electrochemical reconstruction into CoNi oxyhydroxide or layered double hydroxide (LDH), generating the catalytically active species responsible for the high activity and sustained electrocatalytic performance. Moreover, the p-CoNi-BDC_1/NF electrode, fabricated using TPA recovered from waste PET, exhibits electrochemical performance comparable to CoNi-BDC_1/NF synthesized with commercial TPA. This work exemplifies a scalable, sustainable paradigm for transforming polymer waste into value-added chemicals while advancing renewable energy technologies.