Enhanced Methane Sensing Properties of SnO2 Nanoflowers With Ag Doping: A Combined Experimental and First-Principle Study

Ag-doped SnO
₂
nanoflowers (NFs) are prepared via a simple one-step hydrothermal method and subsequent Ag-doping using AgNO
₃
solution as precursors. The crystal structure, morphology and elements of the Ag-doped SnO
₂
NFs are investigated in detail. The maximal response of Ag-doped SnO
₂
sensor with 1.0 wt.% Ag doping to 500 ppm methane is increased by a factor of 1.6 as compared to that of pure SnO
₂
sensor. The long-term stability and the selectivity of the SnO
₂
-based sensor are improved by Ag-doping as well. Meanwhile, pre-adsorption of oxygen molecules on the surface of the SnO
₂
-based substrate is studied in- depth with the method of first-principle calculation. Ag doping lowers adsorption energy for all the adsorption sites, demonstrating a higher adsorption stability of chemisorbed oxygen ions on the Ag-doped SnO
₂
as compared to the pristine phase. More electron transfer from the semiconductor to the chemisorbed oxygen is revealed by the Mulliken charge analysis and the electron density difference for the Ag-doped SnO
₂
, explaining the better sensitivity of gas sensors based on Ag-doped SnO
₂
nanostructures as compared to its undoped counterpart.