Pt Nanoparticles Sensitized Ordered Mesoporous WO₃ Semiconductor: Gas Sensing Performance and Mechanism Study

Abstract

In this study, a straightforward coassembly strategy is demonstrated to synthesize Pt sensitized mesoporous WO 3 with crystalline framework through the simultaneous coassembly of amphiphilic poly(ethylene oxide)-b-polystyrene, hydrophobic platinum precursors, and hydrophilic tungsten precursors. The obtained WO 3 /Pt nanocomposites possess large pore size (≈13 nm), high surface area (128 m 2 g −1 ), large pore volume (0.32 cm 3 g −1 ), and Pt nanoparticles (≈4 nm) in situ homogeneously distributed in mesopores, and they exhibit excellent catalytic sensing response to CO of low concentration at low working temperature with good sensitivity, ultrashort response-recovery time (16 s/1 s), and high selectivity. In-depth study reveals that besides the contribution from the fast diffusion of gaseous molecules and rich interfaces in mesoporous WO 3 /Pt nanocomposites, the partially oxidized Pt nanoparticles that chemically and electronically sensitize the crystalline WO 3 matrix, dramatically enhance the sensitivity and selectivity.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adfm.201705268. metal oxides (SMOs), such as WO 3 , [1] ZnO, [2] SnO 2 , [3] In 2 O 3 , [4] have attracted much attention for their wide applications in monitoring gas leakage, air quality, food safety, and medical diagnosis, [5][6][7][8][9] owing to their excellent properties including easy production, low-cost, long-term stability, and compact size. [10] A fast responserecovery dynamics, high sensitivity, and high selectivity are indispensable to highperformance gas sensors based on SMOs because some toxic and flammable gases (e.g., carbon monoxide), are colorless, odorless and tasteless, and extremely poisonous even at low concentrations. Considering that the gas-sensing process strongly relies on surface reactions between target gases and surface-chemisorbed oxygen species on the sensing layers, rational and controlled synthesis of nanomaterials with high surface areas, tailor-designed structure [11][12][13][14] combined with effective catalytic sensitization [15,16] is a promising approach to develop high-performance sensing sensors.SMO nanomaterials with mesoporous structures are promising candidates for gas sensing nanodevices due to their high specific surface area, highly depleted region in thin pore walls, and highly interconnected and adjustable ordered mesopores. [11,12] The high surface area favors the interaction between gas molecules and the solid porous oxide wall as well as the surface catalytic reaction. Moreover, the well-connected channels and a mesoscale (2−50 nm) pore size are advantageous to gas diffusion due to the facile penetration of gas molecules dominated by Knudsen diffusion. [12] To date, mesoporous SMOs can be synthesized through template-free method or templating method. The former includes sol-gel synthesis procedure, [17] spray pyrolysis, [18] and chemical vapor deposition, [3b] which usually lead to materials with ill-defined porous structur...

Gas Sensors Based on Chemi-Resistive Hybrid Functional Nanomaterials

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