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MXenes are promising supports for anchoring metal single atoms due to their versatile composition, well-defined nanostructures, and suitable conductivity. However, metal single atoms are usually coordinated with surface terminal groups (-O, -OH, -Cl, etc.) of MXenes via conventional wet-impregnation, resulting in limited electronic structure modification. Through a NiCl2 molten salt etching method, we observed that Ni single atoms could be in-situ doped in the lattice of MXenes analogue TiC0.5N0.5 support (denoted as Ni1/TiC0.5N0.5), resulting in much larger charge transfer from Ni atoms to adjacent Ti atoms, and thus increasing the electronic density of these Ti atoms. When used for NO2 sensing, Ni1/TiC0.5N0.5 exhibited excellent response sensitivity (ultra-low limit of detection ~ 10 ppb), selectivity, and good stability at room temperature. This study provides an effective strategy for producing MXenes analogue supported metal single atoms for potential application in gas sensing.
We thank the National Key R&D Program of China (No. 2018YFA0208504), the National Natural Science Foundation of China (Nos. 21932006 and 92161112), the National Science Basic Research Program of Shaanxi (Nos. S2020-JC-WT-0001 and 2021JCW-20), and the Youth Innovation Promotion Association of CAS (No. Y2017049) for financial support. We thank the beamline 1W1B station in Beijing Synchrotron Radiation Facility (BSRF) and Dr. Lirong Zheng for help in XAFS characterization.