Rational Synthesis and Gas Sensing Performance of Ordered Mesoporous Semiconducting WO3/NiO Composites

Semiconducting metal oxides have attracted increasing attention in various fields due to their intrinsic properties. In this study, a facile solvent evaporation-induced multicomponent co-assembly approach coupled with a carbon-supported crystallization strategy is employed to controllably synthesize crystalline mesoporous nickel oxide-doped tungsten oxides in an acidic THF/H2O solution with poly(ethylene oxide)-b-polystyrene diblock copolymers (PEO-b-PS) as the structure-directing agent, tungsten(VI) chlorides as WO3 precursors, and Ni(AcAc)2 as the NiO precursor. The obtained materials possess a face-centered cubic mesoporous structure, large pore size (∼30 nm), high surface area (30–50 m2 g–1), large pore volume (0.15–0.19 cm3 g–1), and ultralarge pore windows (12–16 nm) connecting adjacent mesopores, and the mesoporous WO3 framework was decorated by ultrafine NiO nanocrystals. Due to their well-connected porous structure and high surface areas with rich WO3–NiO interfaces, the composite materials exhibit superior gas sensing performance with an ultrafast response (∼4 s), high sensitivity (Ra/Rg = 58 ± 5.1), and selectivity to 50 ppm H2S at a relatively low working temperature (250 °C). The chemical mechanism study reveals complicated surface reactions of WO3/NiO-based gas sensors, and SO2, WS2, and NiS intermediates were found to be generated during the gas sensing process.