Engineering Pore Walls of Mesoporous Tungsten Oxides via Ce Doping for the Development of High-Performance Smart Gas Sensors

Chemiresistive gas sensors are widely used in environmental monitoring and industry production; however, their selectivity and sensitivity are yet to be improved and their working temperature is usually too high (around 250 °C), which limit their applications in detecting trace gases at low temperatures due to the low activity of sensitive layers. Herein, novel Ce-doped mesoporous WO3 with high specific surface areas of 59–72 m2/g, a stable crystalline framework, and finely tailored pore walls was synthesized via a facile in situ cooperative assembly method combined with a carbon-supported crystallization strategy. The doping of Ce atoms in the mesoporous WO3 pore wall can effectively adjust the coordination environment of W atoms, giving rise to dramatically enhanced oxygen vacancy (Ov) and forming Wδ+-Ov sites. As a result, the obtained Ce-doped mesoporous WO3 showed excellent H2S sensing performance at a low working temperature (150 °C) with an ultrahigh response value (381 vs 50 ppm), fast response dynamics (6 s), outstanding selectivity, and antihumidity property as well as good long-term stability. The superior gas sensing performance is attributed to the increased Ov density and enhanced conversion of surface-adsorbed H2S into SOx and SOx2– during the surface adsorption-catalysis reaction in the sensitive layer. Density functional theory (DFT) calculations reveal that Ce4+ is embedded into the crystal lattice of WO3 to form an optimal structure rather than atom substitution, and Ce-doped WO3 shows a higher H2S adsorption energy and a larger charge transfer than that in pure WO3, accounting for the better H2S sensing response of Ce4+-doped WO3. Furthermore, a novel gas sensing module and smart portable sensor device based on Ce-doped mesoporous WO3 was developed for efficient real-time monitoring of H2S concentration on a smartphone via Bluetooth communication.