Liu Guangdi,Cui Xiuxiu,Yao Lijia,Zhao Rongjun,Tian Xu,Li Diquan,Sun Chunyan,Wang Yude
This paper reports the synthesis of ZnO-SnO 2 nanocomposites modified by PdO nanoparticles named PdO-ZSO which are prepared by the one-step hydrothermal method at 160 °C for 12 h and gas sensing test to H 2 and C 4 H 10 inflammable gas. Meanwhile, PdO-ZSO nanoparticles are XRD, SEM, TEM, EDS, XPS and other characterization methods to further explain its morphological formation process. As the sensing materials, PdO-ZSO exhibits extraordinary gas sensing behaviors for hydrogen (H 2 ) and butane (C 4 H 10 ) and the response reaches 98 and 58 to H 2 and C 4 H 10 at operating temperature of 370 °C, respectively. And the response time and recovery time are both less than 2 s and 4 s respectively, with good repeatability and outstanding long-term stability. The existence of PdO is able to increase the resistance modulation range of heterostructure. And the enhanced gas sensing performances can be ascribed to the catalysis of noble metal doping and the formation of ternary heterostructure between PdO and ZnO-SnO 2 nanocomposites.
Nan Zhang,Yang Lu,Yizhuo Fan,Jingran Zhou,Xin Li,Samira Adimi,Caixia Liu,Shengping Ruan
Designing novel structures and selecting the right catalyst play significant roles to overcome the inherent limitations of chemical sensors. The transition metal-organic framework is one of the most promising precursors for the development of advanced gas sensors with high porosity. In this work, novel ZnO/ZnCo 2 O 4 hetero-structured microspheres synthesized from a Zn–Co-Prussian blue analog (PBA) precursor is rationally designed by changing the temperature of thermal treatment and the decoration of PdO nanoparticles is carried out by a water bath strategy. Formaldehyde-sensing properties of the sensors based on pure ZnCo 2 O 4 NPs, ZZCO-500, ZZCO-700, and PdO-ZZCO microspheres are studied in detail. The experiment results show that the PdO-ZnO/ZnCo 2 O 4 microsphere-based sensor has a higher response value (about 26.9), better selectivity (S formaldehyde /S ethanol = 5) and rapid response and recovery (9/14 s) towards 100 ppm formaldehyde as well as a low detection limit (0.2 ppm). The improvement in formaldehyde-sensing properties could be attributed to the larger specific surface areas (SSA), abundant active sites, the heterojunctions and the catalytic effect of PdO nanoparticles. This work provides a feasible method for synthesizing MOF-derived hetero-structured nanomaterials, demonstrating the potential application for monitoring indoor air pollutants.
A post-synthetic modification strategy for anchoring PdO nanoparticles on the Beta zeolite surface and obtaining stable and highly dispersed PdO sites with abundant active Pd n+ (0 < n < 2) species was reported. The modified Beta supported Pd catalyst with a 0.94 wt% Pd loading amount shows (>) 99% methane conversion at 375 °C with a space velocity of 30,000 mL h −1 g −1 and a satisfied long-term (>30 h) CH 4 oxidation stability at 340 °C. Such a post-synthetic strategy provides a new way to disperse and stabilize noble metal particles on zeolite support for harsh catalytic process.
The MgO-doped hexagonal boron nitride (MgO-h-BN) nanomaterials were designed as a support for Palladium (Pd) catalysts for CO oxidation reaction. The catalytic properties of Pd/MgO(5)-h-BN catalyst was investigated and compared with Pd/h-BN catalyst. Transmission electron microscopy (TEM) results suggested that the PdO nanoparticles with small grain sizes (ca. 8 nm) were effectively dispersed on the surface of MgO, and the MgO were deposited on the h-BN nanosheets in the Pd/MgO(5)-h-BN catalyst. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses revealed that a small amount of Mg 2+ embedded into the B vacancies of h-BN nanosheets in the Pd/MgO(5)-h-BN catalyst. More significantly, a large amount of adsorbed oxygen appeared near the B vacancies of Pd/MgO(5)-h-BN catalyst. The experiments outcomes of diffuse reflectance fourier transform spectra analysis of CO (CO-DRIFT) indicated that the carbonate/formate species were easily decomposed to CO 2 on the Pd/MgO(5)-h-BN catalyst than Pd/h-BN catalyst, which might be a reason why the Pd/MgO(5)-h-BN catalyst had high CO oxidation activity. According to above analyses, we provide a new insight for the MgO-h-BN nanomaterials for Pd catalysts for application in CO oxidation reaction.
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