Cation‐Vacancy Engineering in Cobalt Selenide Boosts Electrocatalytic Upcycling of Polyester Thermoplastics at Industrial‐Level Current Density

Abstract The past decades have witnessed the increasing accumulation of plastics, posing a daunting environmental crisis. Among various solutions, converting plastics into value‐added products presents a significant endeavor. Here, an electrocatalytic upcycling route that efficiently converts waste poly(butylene terephthalate) plastics into high‐value succinic acid with high Faradaic efficiency of 94.0% over cation vacancies‐rich cobalt selenide catalyst is reported, showcasing unprecedented activity (1.477 V vs. RHE) to achieve an industrial‐level current density of 1.5 A cm⁻², and featuring a robust operating durability (≈170 h). In particular, when combining butane‐1,4‐diol monomer oxidation (BOR) with hydrogen evolution using the cation vacancy‐engineered cobalt selenide as bifunctional catalyst, a relatively low cell voltage of 1.681 V is required to reach 400 mA cm⁻², manifesting an energy‐saving efficiency of ≈15% compared to pure water splitting. The mechanism and reaction pathways of BOR over the vacancies‐rich catalyst are first revealed through theoretical calculations and in‐situ spectroscopic investigations. The generality of this catalyst is evidenced by its powerful electrocatalytic activity to other polyester thermoplastics such as poly(butylene succinate) and poly(ethylene terephthalate). These electrocatalytic upcycling strategies can be coupled with the reduction of small molecules (e.g., H₂O, CO₂, and NO₃⁻), shedding light on energy‐saving production of value‐added chemicals.