title: Kilogram-scale synthesis of Pd-loaded quintuple-shelled Co3O4 microreactors and their application to ultrasensitive and ultraselective detection of methylbenzenes.
abstract: We report the kilogram-scale, simple, and cost-effective synthesis of Pd-loaded quintuple-shelled Co3O4 microreactors by spray drying of aqueous droplets containing cobalt nitrate, palladium nitrate, citric acid, and ethylene glycol and subsequent heat treatment. Highly viscous gel spheres containing Co and Pd salts were successfully converted into multi thin-shelled Co3O4 reactors uniformly loaded with Pd catalysts by the sequential combustion of carbon and decomposition of the metal salts from the outer to the inner regions during one-step heat treatment. The responses (resistance ratio) of the Pd-loaded quintuple-shelled Co3O4 microreactors to 5 ppm toluene and p-xylene were 30.8 and 64.2, respectively, and the selectivity values to toluene and p-xylene against ethanol interference (response ratio) were 14.5 and 30.1, respectively. The unprecedented high response and selectivity were attributed to the effective dissociation of less reactive methylbenzenes into more active smaller species assisted both by catalytic Co3O4 and Pd during the prolonged retention within the microreactors. Kilogram-scale preparation of noble metal-loaded multishelled microreactors and their unique gas-sensing characteristics based on a novel microreactor concept can pave a new way to design of high-performance gas sensors for practical applications.
authors: †Department of Materials Science and Engineering, Korea University, Seoul 136-713, Republic of Korea.
authors: Ji-Wook
authors: JW
authors: Yoon
authors: †Department of Materials Science and Engineering, Korea University, Seoul 136-713, Republic of Korea.
authors: Young Jun
authors: YJ
authors: Hong
authors: †Department of Materials Science and Engineering, Korea University, Seoul 136-713, Republic of Korea.
authors: Gi Dae
authors: GD
authors: Park
authors: †Department of Materials Science and Engineering, Korea University, Seoul 136-713, Republic of Korea.
authors: Su-Jin
authors: SJ
authors: Hwang
authors: ‡Department of Chemical and Materials Engineering, King Abdulaziz University, Jeddah 21589, Saudi Arabia.
authors: Faissal
authors: F
authors: Abdel-Hady
authors: ‡Department of Chemical and Materials Engineering, King Abdulaziz University, Jeddah 21589, Saudi Arabia.
authors: AbdulAziz A
authors: AA
authors: Wazzan
authors: †Department of Materials Science and Engineering, Korea University, Seoul 136-713, Republic of Korea.
authors: Yun Chan
authors: YC
authors: Kang
authors: †Department of Materials Science and Engineering, Korea University, Seoul 136-713, Republic of Korea.|‡Department of Chemical and Materials Engineering, King Abdulaziz University, Jeddah 21589, Saudi Arabia.
authors: Jong-Heun
authors: JH
authors: Lee
keywords: Pd-loaded Co3O4; gas sensor; kilogram-scale preparation; methylbenzenes; selectivity; yolk−shell microreactor