Defective nickel sulfide hierarchical structures for efficient electrochemical conversion of plastic waste to value-added chemicals and hydrogen fuel

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Abstract
Valorizing plastic waste into value-added chemicals/fuels in a green manner (e.g., electrochemical reforming) is a sustainable way to address the global pressing problem of plastic pollution. For the electro-reforming of plastic waste (e.g., polyethylene terephthalate (PET)), the development of highly active and selective catalysts remains a challenge. Herein, we have designed a low-cost and highly defective nickel sulfide to selectively convert ethylene glycol (PET monomer) into formate, with the co-production of hydrogen fuel. The optimal B and Co co-doped Ni3S2 (B,Co-NiS) only takes 1.341 V compared to the reversible hydrogen electrode (RHE) at 100 mA cm−2 for ethylene glycol oxidation, and it can realize high faradaic efficiency (>93%) and selectivity (>92%) for EG-to-formate conversion over a wide potential range. Furthermore, the bifunctional B,Co-NiS assisted real PET waste hydrolysate electrolysis in a membrane-electrode assembly (MEA) can generate 15.24 mmol formate per hour and attain H2 production efficiency over 70 times compared to conventional water electrolysis. Mechanism analyses indicate that the excellent catalytic performance of B,Co-NiS stems from the hierarchical structure, rich S defective sites, regulated electronic properties, and the dopant-facilitated in situ formation of an active sulfide@oxyhydroxide phase. This work provides an integrated nanostructure controlled-composition regulation strategy to design cost-effective catalysts for plastic electro-upcycling and paves the way for low-carbon plastic waste management.
Funding Information
  • Australian Research Council (DP220101139)
  • Australian Research Council (DE220100530)

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