A two-channel thermal dissociation cavity ring down spectroscopy （CRDS） instrument has been built for in situ, real-time measurement of NO2 and total RNO2 （peroxy nitrates and alkyl nitrates） in ambient air, with ...A two-channel thermal dissociation cavity ring down spectroscopy （CRDS） instrument has been built for in situ, real-time measurement of NO2 and total RNO2 （peroxy nitrates and alkyl nitrates） in ambient air, with a NO2 detection limit of 0.10 ppbv at 1 s. A 6-day long measurement was conducted at urban site of Hefei by using the CRDS instrument with a time resolution of 3 s. A commercial molybdenum converted chemiluminescence （Mo-CL） instrument was also used for comparison. The average RNO2 concentration in the 6 days was measured to be 1.94 ppbv. The Mo-CL instrument overestimated the NO2 concentration by a bias of ＋1.69 ppbv in average, for the reason that it cannot distinguish RNO2 from NO2. The relative bias could be over 100% during the afternoon hours when NO2 was low but RNO2 was high.展开更多
Pt-based nanoframes represent a class of promising catalysts towards oxygen reduction reaction. Herein, we, for the first time, successfully prepared Pt-Pd octahedral nanoframes with ultrathin ridges less than 2 nm in...Pt-based nanoframes represent a class of promising catalysts towards oxygen reduction reaction. Herein, we, for the first time, successfully prepared Pt-Pd octahedral nanoframes with ultrathin ridges less than 2 nm in thickness. The Pt-Pd octahedral nanoframes were obtained through site-selected deposition of Pt atoms onto the edge sites of Pd octahedral seeds, followed by selective removal of the Pd octahedral cores via chemical etching. Due to that a combination of three-dimensional opens geometrical structure and Pt-skin surface compositional structure, the Pt-Pd octahedral nanoframes/C catalyst shows a mass activity of 1.15 A/mgPt towards oxygen reduction reaction, 5.8 times enhancement in mass activity relative to commercial Pt/C catalyst （0.20 A/mgPt）. Moreover, even after 8000 cycles of accelerated durability test, the Pt-Pd octahedral nanoframes/C catalyst still exhibits a mass activity which is more than three times higher than that of pristine Pt/C catalyst.展开更多
文摘A two-channel thermal dissociation cavity ring down spectroscopy （CRDS） instrument has been built for in situ, real-time measurement of NO2 and total RNO2 （peroxy nitrates and alkyl nitrates） in ambient air, with a NO2 detection limit of 0.10 ppbv at 1 s. A 6-day long measurement was conducted at urban site of Hefei by using the CRDS instrument with a time resolution of 3 s. A commercial molybdenum converted chemiluminescence （Mo-CL） instrument was also used for comparison. The average RNO2 concentration in the 6 days was measured to be 1.94 ppbv. The Mo-CL instrument overestimated the NO2 concentration by a bias of ＋1.69 ppbv in average, for the reason that it cannot distinguish RNO2 from NO2. The relative bias could be over 100% during the afternoon hours when NO2 was low but RNO2 was high.
基金This work is supported by Collaborative Innovation Center of Suzhou Nano Science and Technology, Ministry of Science and Technology of China （No.2014CB932700）, the National Natural Science Foundation of China （No.21603208, No.21573206, and No.51371164）, the China Postdoctoral Science Foundation （No.2015M580536, No.2016T90569）, Key Research Program of Frontier Sciences, CAS （QYZDBSSW- SLH017）, Strategic Priority Research Program B of the CAS （No.XDB01020000）, Hefei Science Center, CAS （No.2015HSC-UP016）, and Fundamental Research Funds for the Central Universities.
文摘Pt-based nanoframes represent a class of promising catalysts towards oxygen reduction reaction. Herein, we, for the first time, successfully prepared Pt-Pd octahedral nanoframes with ultrathin ridges less than 2 nm in thickness. The Pt-Pd octahedral nanoframes were obtained through site-selected deposition of Pt atoms onto the edge sites of Pd octahedral seeds, followed by selective removal of the Pd octahedral cores via chemical etching. Due to that a combination of three-dimensional opens geometrical structure and Pt-skin surface compositional structure, the Pt-Pd octahedral nanoframes/C catalyst shows a mass activity of 1.15 A/mgPt towards oxygen reduction reaction, 5.8 times enhancement in mass activity relative to commercial Pt/C catalyst （0.20 A/mgPt）. Moreover, even after 8000 cycles of accelerated durability test, the Pt-Pd octahedral nanoframes/C catalyst still exhibits a mass activity which is more than three times higher than that of pristine Pt/C catalyst.
