Stable and highly selective Co-CeF₃@Ni₃N sheet-on-sheet heterostructures for PET electro-upgrading and hydrogen production

The electro-upgrading of polyethylene terephthalate (PET) alkaline hydrolysate provides an energy-saving strategy towards green hydrogen and value-added anodic products, but the selectivity and stability at industrial-scale current densities (>200 mA cm^-2) remain challenging. Herein, hierarchical Co-CeF₃@Ni₃N sheet-on-sheet nanostructures supported on nickel foam (Co-CeF₃@Ni₃N/NF) were fabricated for PET hydrolysate electro-upgrading coupled with H₂ generation. The hierarchical nanostructures can enlarge the accessible active area, while the introduction of Co species can modulate the electronic configuration, which can reduce the active species formation potential and optimize the adsorption behaviors of key reactants and reactive intermediates. Therefore, Co-CeF₃@Ni₃N/NF exhibits industrial-scale response current densities (80 to 380 mA cm^-2) at applied potentials of around 1.32-1.44 V <i>vs.</i> RHE, as well as high stability (over 60 h) and high faradaic efficiencies (>97%) in the ethylene glycol oxidation reaction (EGOR), which are superior to most high-end electrocatalysts. <i>In situ</i> characterizations and electrochemical measurements indicate the key active species and crucial intermediates in the EGOR, suggesting a reaction pathway towards high formate selectivity. Moreover, a continuous flow cell with Co-CeF₃@Ni₃N/NF as the bifunctional electrode for electro-upgrading PET hydrolysate delivers high activity (over 300 mA cm^-2 at 1.72 V), long-term stability (144 h) and high FEs (>95%). This study develops a bifunctional electrocatalyst for the EGOR and HER, while elucidating the active species, key intermediates, and possible reaction pathway for the closed-loop electro-upgrading of PET waste.