Continuous polypyrrole nanotubes encapsulated Co₃O₄ nanoparticles with oxygen vacancies and electron transport channels boosting peroxymonosulfate activation

Co₃O₄ particles are promising heterogeneous catalysts for peroxymonosulfate (PMS) activation; whereas they still surfer from the extensive agglomeration, serious Co leaching, poor electronic conductivity, and difficult recovery. Herein, a novel hybrid nanoarchitectonic constructed by encapsulating Co₃O₄ nanoparticles into continuous polypyrrole (PPy) nanotubes (Co₃O₄@PPy hybrids) was developed using electrospun fibers as the templates, which boosted the catalytic degradation toward tetracycline (TC). The continuous polypyrrole nanotubes could provide the confined spaces, offer effective electron transfer pathway, suppress cobalt ion loss, facilitate the oxygen vacancy (O_vac) formation, and accelerate the Co²⁺/Co³⁺ cycles. Co₃O₄@PPy hybrids thereby exhibited a remarkably enhanced catalytic activity with the TC degradation efficiency of 97.2% (k_obs = 0.244 min⁻¹) within 20 min and total organic carbon (TOC) removal rate of 66.8%. Furthermore, the recycle test, real natural water treatment, and fluidized-column catalytic experiments indicated the potential of Co₃O₄@PPy hybrids in the practical large-scale applications.