Vacancy-defective spinel NiCo2O4 enables high-valent Ni/Co species and adsorbate binding for the electrocatalytic upcycling of polybutylene succinate plastics

Abstract

Electroreforming polybutylene succinate (PBS) plastics waste and NOx into value-added chemicals is a promising strategy to mitigate environmental pollution. However, achieving high activity and controllable selectivity remains challenging especially at industrially relevant current densities, due to the complex multi-step dehydrogenation of alcohol intermediates and competing oxygen evolution reaction. Here, we report a vacancy-defective spinel-type NiCo2O4 electrocatalyst for the enhanced electrooxidation of 1,4-butanediol, a monomer derived from PBS plastic. Mechanistic studies revealed that the catalyst facilitates the generation of high-valent Ni/Co species and regulates the adsorption of oxygen-containing intermediates, thereby boosting catalytic activity via a OH*-participated mechanism. By pairing PBS hydrolysate oxidation with NOx reduction reaction in a membrane electrode assembly, the system achieved a cell voltage of 1.42 V at 400 mA cm-2, while maintaining continuous operation for over 100 hours with combined Faradaic efficiencies exceeding 175%. High-purity SA and NaHCO3 products can be separated from the post-reaction anolyte via CO2-assisted acidification-precipitation. The obtained SA can further react with concentrated NH3 in the catholyte to yield valuable succinimide. This work provides a practical approach for the efficient upcycling of sustainable plastic and NOx into valuable products, enabled through tailored catalyst design and system configuration.