Isolated Ir-Se Sites in Nickel Selenide for Glyoxal-Mediated Ethylene Glycol Oxidation to Formate and PET Upcycling

The accumulation of plastic waste presents a persistent environmental challenge, motivating the development of strategies that integrate its remediation and upcycling. As a principal monomer derived from poly(ethylene terephthalate) (PET), ethylene glycol (EG) serves as a key platform substrate for the electrochemical upcycling of PET waste into value-added chemicals. In this study, nickel selenide (NiSe) was synthesized via pulsed laser irradiation in liquids, and atomically dispersed iridium (Ir) sites coordinated with selenium (Se) were introduced into the cationic sites of NiSe to regulate its intrinsic activity toward the electrocatalytic EG oxidation reaction. The Ir/NiSe-2 catalyst oxidizes EG to formate via bidentate adsorption followed by a glyoxal-mediated pathway, achieving a Faradaic efficiency of 83.09% at 1.60 V versus RHE, together with a formate yield rate of 1248 µmol cm^-2 h^-1. In situ Raman spectroscopy reveals an earlier onset of catalytically active NiOOH formation in Ir/NiSe-2 compared to NiSe, evidencing Ir-promoted modulation of the NiSe surface electronic structure. When coupled with Pt/C for the hydrogen evolution reaction in a two-electrode configuration, the system sustains continuous electrolysis, producing formate and green hydrogen. After extended electrolysis, terephthalic acid and potassium diformate were recovered from the anolyte, demonstrating a viable route for PET upcycling into value-added products.