Electronic and catalytic properties of Ti single atoms@SnO2 and its implications on sensing mechanism for CO

Inspired by the unprecedented catalyzing effect of single-atom catalysts, the atomically scattered Ti single-atom significantly enhancing the CO sensing performance of the SnO2(1 1 0) are investigated by using DFT-D calculations. The Ti single-atom prefers to stay on the top layer of six-fold Sn atoms. Two reaction mechanisms for CO oxidation are found on the Ti single -atom doped SnO2(1 1 0) with the moderate reaction barriers of 0.53 eV (Path I) and 0.83 eV (Path II), respectively for the rate-determining steps. The Ti single -atom doped SnO2(1 1 0) can be active and selective sensing catalyst for CO oxidation with their activation barrier (0.53 eV) is comparable with those of Pt6c/SnO2 (0.62 eV) and In-doped SnO2(1 1 0) (1.03 eV). Furthermore, the microkinetic investigation reveals that the maximum CO oxidation rate along the Path I is 4.29 x 104 s-1. This finding suggests that Ti single-atom doping can effectively improve CO oxidation at low-temperature, hence improving the SnO2 to CO sensing performance. Our study enlightens the perspective application of single-atom catalysts on gas sensing fields and provides new routes for designing new gas sensing materials.