Abstract
The extensive use of chlorobenzene in chemical, pharmaceutical, and agrochemical industries poses a severe health hazard to human beings, because it is highly toxic. The detection of chlorobenzene by metal oxide gas sensors is difficult, owing to its chemically inert molecular structure. In this study, well-dispersed Pd nanoparticles were deposited on porous ZnO nanoplates via surface ion exchange, followed by H2 reduction. The preparation process effectively prevented the aggregation and uncontrollable growth of Pd particles. A gas-sensing test was conducted, and the modification of size-controlled Pd nanoparticles was found to effectively enhance the sensing properties of porous ZnO nanoplates to chlorobenzene over 300 °C (higher sensitivity at a low operating temperature). At 440 °C, 5% Pd@ZnO sensor showed a drastic increase in response by nearly 4.5-fold, as well as excellent sensing selectivity to chlorobenzene. Its repeatability and stability were acceptable. As known, Pd nanocatalysts contribute to the oxidation of chlorinated aromatic compounds. Pd@ZnO sensors generated more catalytic sites and oxygen species (confirmed by XPS), thus enhancing chlorobenzene oxidation and improving the sensitivity of ZnO-based gas sensors.
Highlights
Chlorobenzene has widespread applications in chemical and pharmaceutical industries
A er H2 reduction, the X-ray diffractometer (XRD) patterns of Pd@ZnO display new peaks corresponding to the Pd (111) and (200) lattice planes (JCPDS, no. 46-1043)
These results show that the Pd nanoparticles are size-controlled and well-dispersed on porous ZnO nanoplates
Summary
Chlorobenzene has widespread applications in chemical and pharmaceutical industries. It is a highly toxic and healththreatening chemical.[1] Its detection is important for maintaining standard environmental conditions and avoiding environmental hazards. Gas chromatography is the generally routine technique utilized for chlorobenzene detection.[2] rapid on-site monitoring of VOCs (volatile organic chemicals) free from pretreatment is pursued.[3] Gas-sensing technology has these advantages. Gas detection by semiconductors is a method that converts electrons into electrical signals by redox reaction of target gas molecules on the surfaces of gas sensors.[4] The simple electronic gas-sensing system is prominent candidate for use in chlorobenzene detection.[5] The development of gas-sensitive materials is the key, and the research on metal-oxide-based gas sensors has attracted much attention.[6]
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