Construction of 0D Zinc Oxide Nanoparticles Anchored on the Surface of 2D MXene Functional Materials for High-efficiency Photocatalytic Removal of Organic Pollutants: Roles of Nanoconfinement Effect and Interface Effect
Abstract
Zinc oxide (ZnO) nanoparticles anchored onto the MXene surface (ZnO/MXene photocatalysts) were synthesized via hydrofluoric acid etching and solventthermal method. The photocatalytic performance of ZnO/MXene composites was evaluated by degrading methyl orange (MO) and p-nitrophenol (p-NP). MXene has a lamellar structure, while ZnO nanoparticles mostly form aggregated spheres. The ZnO/MXene composite maintains this lamellar morphology, with aggregated spherical ZnO nanoparticles on the surface, edges, and interlayer spaces of lamellar structure, thus forming a sandwich-like composite. When the mass ratio of ZnO to MXene in ZnO/MXene composite is 1:1 and catalyst dosage is 0.5 g·L-1 or 0.7 g·L-1, the optimal removal rates for MO and p-NP reach 100% and 74%, respectively. Compared to individual MXene and ZnO, the ZnO/MXene composite shows enhanced photocatalytic activity. This can be attributed to the nanoconfinement effect of MXene and interface interactions between ZnO and MXene. The change in surface charge distribution mainly stems from the S=O bond for MO, causing an increase in energy gap and chemical hardness of its degradation intermediates. However, the surface charge distribution changes are mainly due to the N=O bond for p-NP, resulting in increased the highest occupied molecular orbital (EHOMO) values and chemical potential, while the electronegativity and Electrophilicity indices decrease in its degradation intermediates.