Chromium-Modified Nickel Sulfide Catalysts Enable Energy-Efficient Electrochemical Polyethylene Terephthalate Upcycling

Despite recent stunning progress in electrocatalytic valorization of plastics, it remains a huge challenge to develop highly active electrocatalysts for achieving industrial-level current density. Herein, a flocculent chromium-modified nickel sulfide (Cr-Ni₃S₂-Ni(OH)₂/NF) immobilizing on nickel foam and scrutinize its electrocatalytic activity for oxidation of ethylene glycol monomers (EOR) of polyethylene terephthalate (PET) is crafted. The Cr-Ni₃S₂-Ni(OH)₂/NF catalyst facilitates efficient formate production at an industrial-level current density of 1200 mA cm⁻², requiring a record low potential of 1.561 V (vs. RHE). A series of in-situ spectroscopy in conjunction with theoretical calculations substantiates that the high activity of the catalyst originates from the regulated d-band center of Ni by Cr and S species. Hybrid electrosynthesis systems coupling EOR and cathodic CO₂ or H₂O reduction reaction (CO₂RR or HER) are subsequently assembled. When reaching 400 mA cm⁻², CO₂RR//EOR electrolyzer enables coproduction of formate at an impressively low cell voltage of 2.694 V, avoiding ion-exchange membrane and product crossover. Rigorous techno-economic evaluation reveals that the attractive profitability of these two electrosynthesis routes reverses the long-term dilemma of negative profits. This work paves a green and sustainable avenue toward the valorization of low-grade carbon resources.