Multi-interface Mn3O4@ZnO/TiO2 with controllable charge transfer routes for highly selective denitrification under ultrasonic-assisted visible light photocatalysis

Interfacial effect played a critical role in catalytic reactions for environmental remediation. An innovative Mn3O4@ZnO/TiO2 heterojunction with multi-interface structure was precisely-designed for the first time through alternate growth of ZnO and TiO2 nanolayers on Mn3O4 surface by atomic layer deposition. Further, the catalytic property of Mn3O4@ZnO/TiO2 was evaluated through denitrification from water under ultrasonicassisted visible light photocatalysis, which achieved 98.6% NO3--N reduction and 98.8% N-2 selectivity within 120 min. Besides, the Mn3O4@ZnO/TiO2 exhibited stability and recyclability during the denitrification process. Mechanism insight revealed significant contributions of the novel multi-interface type II heterojunction. More charge transfer routes and possible reaction interfaces were provided for selective denitrification. Equally important, the synergy between visible light and ultrasound promoted the generation of active radicals. The radical trapping experiment proved the dominate role of e(-) and center dot C2O center dot- in the denitrification process. Overall, the Mn3O4@ZnO/TiO2 appeared to be a promising candidate to remediate aquatic contaminants in ultrasonic-assisted photocatalytic system. Also, this study highlighted an attractive approach for controllable fabrication of multi-interface heterojunctions.