Bismuth MOFs based hierarchical Co3O4-Bi2O3 composite: An efficient heterogeneous peroxymonosulfate activator for azo dyes degradation

A hierarchical Co 3 O 4 -Bi 2 O 3 composite was first prepared via an adsorption-calcination method using a bismuth-based MOF (Bi-BTC) as the precursor and substrate. In the composite, Co 3 O 4 nanoparticles are loaded on the outer layer of Bi 2 O 3 rods derived from Bi-BTC and show a uniform honeycomb-like morphology. In dyes degradation tests, the Co 3 O 4 -Bi 2 O 3 composite exhibits much better peroxymonosulfate (PMS) activation performance in RhB degradation than pure Bi 2 O 3 or Co 3 O 4 . The Co 3 O 4 -Bi 2 O 3 /PMS system also shows high performance for various azo dyes and maintains good catalytic performance at wide pH range. Besides, the good chemical stability of Co 3 O 4 -Bi 2 O 3 ensures it good reusability in four recycling tests. XPS and electrochemical analysis indicate the interaction of Bi species promotes the activation capacity of Co 3 O 4 nanoparticles. The results of radicals quenching tests and ESR analysis reveal the singlet oxygen and superoxide radicals are the dominant functional radical species in Co 3 O 4 -Bi 2 O 3 /PMS system and subsequently a reasonable activation mechanism is proposed.