Au-decorated WO3-based sensor for chemiresistive detection of NO2 at 80 °C

Nitrogen dioxide (NO2), a hazardous gas of acidic nature, is constantly released into the atmosphere by human activities. Based on the noble metal sensitization, the NO2 sensing performance of Au decorated WO3 sensors (Rg/Ra = 4.3@ 1 ppb, 746.0@ 5 ppm) was found to be superior to that of pristine WO3 (Rg/Ra = 1.2@ 1 ppb). In addition, the dynamic processes that occur in Au–WO3-3 during NO2 sensing reactions were analyzed using ex-situ X-ray photoelectron spectroscopy. Density functional theory containing adsorption energy, is further used to analyse mechanism accurate electron transfer sensing process. Furthermore, the effects of the oxygen partial pressure and relative humidity on the sensing performance of the sensors were studied. The enhanced sensing mechanisms of Au–WO3 sensors can be attributed to the electronic and chemical sensitization effects of Au, increased number of active sites, decrease in the activation energy of the sensing reactions and three-dimensional hierarchical structure, which boosts the adsorption of gas molecules and charge transfer efficiency.