Synergistic Effects of Oxygen Defects and p–n Heterojunctions in CuO@Ni(OH) _{2– <i>x</i>} Core–Shell Nanowires for Efficient Electrooxidation of PET Plastics and Biomass-Derived Alcohols

Nickel-based materials exhibit great potential for electrocatalytic upgrading of poly(ethylene terephthalate) (PET)-derived ethylene glycol (EG) and biomass-derived glycerol (GLY). However, the high energy barrier for generating active species (Ni3+OOH) and their limited ability to activate EG and GLY significantly impede the efficient conversion of EG and GLY. Herein, CuO@Ni(OH)2–x core–shell nanowires with abundant oxygen vacancies and p–n junction interfaces were successfully designed, which exhibited high activity and selectivity for EG/GLY-to-formic acid at industrial-grade current densities. Particularly, for EG electrooxidation, CuO@Ni(OH)2–x offered 300 mA cm–2 at an ultralow potential of 1.58 V vs RHE with ∼99% Faradaic efficiency for HCOOH production. Experimental and theoretical analysis revealed that (1) the oxygen vacancies and p–n junction synergistically mediate the atomic coordination and electronic structure of Ni2+–OH, which facilitates OH– adsorption and decreases the energy barrier of O–H bond cleavage, and hence accelerates the formation of Ni3+OOH; (2) the high exposure of Ni3+ enabled by oxygen vacancies enhances the adsorption of EG/GLY and the cleavage of the C–C bond, which boosts the kinetics of EG/GLY-to-formic acid. As a proof of concept, a solar-driven reactor equipped with a “one-click” operating system was designed for the upcycling of real-world PET bottles, achieving a Faradaic efficiency of 86.7% for HCOOH. This work underlines the synergistic regulation of defects and p–n junctions in nickel-based electrocatalysts for efficient PET and biomass-derived alcohol electrooxidation.