Modulating Electronic Structure and Morphology in Nb-NiCoS for PET Plastic Upcycling

Electrocatalytic polyethylene terephthalate (PET) upcycling coupled with green hydrogen production offers an energy-efficient route for plastic waste valorization. Herein, Nb-incorporated NiCoS electrocatalysts are synthesized on nickel foam via a one-step chemical bath deposition route for PET electro-upcycling. Nb incorporation modulates the electronic structure and morphology of NiCoS, producing defect-rich vertically interconnected nanosheets with abundant electrochemically dynamic Ni³⁺/Co³⁺ active sites. The optimized electronic structure promotes reconstruction into active NiOOH/CoOOH species, resulting in enhanced performance toward the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), ethylene glycol oxidation reaction (EGOR), and PET hydrolysate oxidation reaction (POR). Nb-NiCoS requires 1.32 and 1.34 V vs RHE to achieve 100 mA cm^-2 for EGOR and POR, respectively, significantly lower than OER (1.52 V vs RHE). Mechanistic analysis reveals an indirect oxy-hydroxide-mediated oxidation pathway, enabling selective conversion of PET-derived EG into formic acid with a Faradaic efficiency of 93.3% (with ~100% selectivity) and a production rate of 1.16 mmol h^-1 cm^-2 at 100 mA cm^-2. Coupling PET electro-upcycling with hydrogen production reduces the energy consumption to 3.52 kWh Nm^-3 from 4.49 kWh Nm^-3 for conventional water electrolysis, enabling energy saving of 21.3%, highlighting a scalable strategy for simultaneous plastic waste valorization and hydrogen production.