Ag-Functionalized macro-/mesoporous AZO synthesized by solution combustion for VOCs gas sensing application

Abstract

The aim of this paper is to develop easily manufactured and highly sensitive gas sensors for VOCs (volatile organic compounds) detection. Macro-/mesoporous 5 at% Al-doped ZnO (AZO) and Ag-AZO composite powders were prepared by a one-step solution combustion method and used to fabricate gas sensors. Both powders showed the same macro-/mesoporous morphology but have different grain sizes and separated silver phase due to the fast growth of ZnO and the reduction of Ag⁺. The capability of Ag-AZO was investigated for VOCs detection, including n-butanol, methanol, acetone, ethanol, isopropanol and formaldehyde. It is found that the added Ag greatly increases the gas response towards different VOCs. Particularly 2.5 at% Ag-AZO shows the most superior gas sensing performance to 100 ppm VOCs at an operating temperature of 240 °C, which is also the optimum operating temperature of other sensors. The results may be attributed to the synergistic effects of these doped and composite elements, the amount of adsorbed oxygen and the macro-/mesoporous morphology.