Synergistic Features of Superoxide Molecule Anchoring and Charge Transfer on Two-Dimensional Ti₃C₂T_x MXene for Efficient Peroxymonosulfate Activation

The heterogeneous Fenton-like process is regarded as a promising approach to produce reactive oxygen species for water purification and environmental remediation. Here, we report a simple and rational strategy for the design of an efficient catalyst by reducing the dimensionality instead of changing the composition or structure. Based on theoretical and experimental evidence, considerable active sites were exposed on the low-dimensional Ti₃C₂T_x monolayer surface and showed outstanding reactivity toward peroxymonosulfate activation, which was mainly because of the superior compatibility between the highest occupied molecular orbital of catalysts and lowest unoccupied molecular orbital of Oxone. Stimulated emission depletion super-resolution microscopy innovatively provided visual insights into the spatiotemporal heterogeneous activation process and revealed that the unilaminar Ti₃C₂T_x nanosheet exhibited preferable reaction dynamics relative to its inert bulk counterpart, with an aqueous 2,4-dichlorophenoxyacetic acid degradation rate ∼376 times higher than that when using bulk Ti₃C₂T_x as the activator.