In situ quick X-ray absorption spectroscopy(QXAFS) at the Cu and Zn K-edge under operando conditions has been used to unravel the Cu/Zn interaction and identify possible active site of CuO/ZnO/Al_2O_3 catalyst for met...In situ quick X-ray absorption spectroscopy(QXAFS) at the Cu and Zn K-edge under operando conditions has been used to unravel the Cu/Zn interaction and identify possible active site of CuO/ZnO/Al_2O_3 catalyst for methanol synthesis. In this work, the catalyst, whose activity increases with the reaction temperature and pressure, was studied at calcined, reduced, and reacted conditions. TEM and EDX images for the calcined and reduced catalysts showed that copper was distributed uniformly at both conditions. TPR profile revealed two reduction peaks at 165 and 195 °C for copper species in the calcined catalyst. QXAFS results demonstrated that the calcined form consisted mainly of a mixed Cu O and Zn O, and it was progressively transformed into Cu metal particles and dispersed Zn O species as the reduction treatment. It was demonstrated that activation of the catalyst precursor occurred via a Cu^+intermediate, and the active catalyst predominantly consisted of metallic Cu and Zn O evenunder higher pressures. Structure of the active catalyst did not change with the temperature or pressure, indicating that the role of the Zn was mainly to improve Cu dispersion.This indicates the potential of QXAFS method in studying the structure evolutions of catalysts in methanol synthesis.展开更多
Different sizes of layered CoOOH were synthesized by the molten-salt-assisted method at different temperatures.X-ray diffraction and scanning electron microscope studies reveal that CoOOH grew at(003)with increasing t...Different sizes of layered CoOOH were synthesized by the molten-salt-assisted method at different temperatures.X-ray diffraction and scanning electron microscope studies reveal that CoOOH grew at(003)with increasing temperature,and its size can reach dozens of microns.X-ray absorption near edge structure and XPS studies demonstrate that the Co valence state of CoOOH-750 is trivalent,and X-ray Absorption Fine Structure shows that it had a higher symmetry and lower disorder degree,indicating that CoOOH-750 has higher crystallinity and Co3+.The results of electrochemical tests show that CoOOH-750 exhibited the best oxygen-evolution-reaction(OER)catalytic activity.展开更多
Uranyl-organic hybrids,which are assembled from uranyl cations or polynuclear clusters and organic ligands,have gathered tremendous attention driven by their vast array of synthetically accessible structures for custo...Uranyl-organic hybrids,which are assembled from uranyl cations or polynuclear clusters and organic ligands,have gathered tremendous attention driven by their vast array of synthetically accessible structures for customizing their functionality[1].A plethora of uranyl-organic hybrids with their dimensions ranging from OD clusters,1D chains,2D layers and 3D frameworks have been documented in diverse fields including storage,separation,catalysis and sensing[2].展开更多
基金supported by the National Basic Research Program of China(973 Program,2013CB933104)the National Natural Science Foundation of China(Nos.11275258 and 11135008)
文摘In situ quick X-ray absorption spectroscopy(QXAFS) at the Cu and Zn K-edge under operando conditions has been used to unravel the Cu/Zn interaction and identify possible active site of CuO/ZnO/Al_2O_3 catalyst for methanol synthesis. In this work, the catalyst, whose activity increases with the reaction temperature and pressure, was studied at calcined, reduced, and reacted conditions. TEM and EDX images for the calcined and reduced catalysts showed that copper was distributed uniformly at both conditions. TPR profile revealed two reduction peaks at 165 and 195 °C for copper species in the calcined catalyst. QXAFS results demonstrated that the calcined form consisted mainly of a mixed Cu O and Zn O, and it was progressively transformed into Cu metal particles and dispersed Zn O species as the reduction treatment. It was demonstrated that activation of the catalyst precursor occurred via a Cu^+intermediate, and the active catalyst predominantly consisted of metallic Cu and Zn O evenunder higher pressures. Structure of the active catalyst did not change with the temperature or pressure, indicating that the role of the Zn was mainly to improve Cu dispersion.This indicates the potential of QXAFS method in studying the structure evolutions of catalysts in methanol synthesis.
基金This work was supported by“Transformational Technologies for Clean Energy and Demonstration”,Strategic Priority Research Program of the Chinese Academy of Sciences(Grant no.XDA21080200).
文摘Different sizes of layered CoOOH were synthesized by the molten-salt-assisted method at different temperatures.X-ray diffraction and scanning electron microscope studies reveal that CoOOH grew at(003)with increasing temperature,and its size can reach dozens of microns.X-ray absorption near edge structure and XPS studies demonstrate that the Co valence state of CoOOH-750 is trivalent,and X-ray Absorption Fine Structure shows that it had a higher symmetry and lower disorder degree,indicating that CoOOH-750 has higher crystallinity and Co3+.The results of electrochemical tests show that CoOOH-750 exhibited the best oxygen-evolution-reaction(OER)catalytic activity.
基金supported by the National Natural Science Foundation of China(22322609,U22B20139,22206196,and 22076196)the Shanghai Sailing Program(21YF1456200).
文摘Uranyl-organic hybrids,which are assembled from uranyl cations or polynuclear clusters and organic ligands,have gathered tremendous attention driven by their vast array of synthetically accessible structures for customizing their functionality[1].A plethora of uranyl-organic hybrids with their dimensions ranging from OD clusters,1D chains,2D layers and 3D frameworks have been documented in diverse fields including storage,separation,catalysis and sensing[2].
