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Yu-Piao Wang

Bio: Yu-Piao Wang is an academic researcher from National Tsing Hua University. The author has contributed to research in topics: Copper oxide & Yttria-stabilized zirconia. The author has an hindex of 2, co-authored 2 publications receiving 455 citations.

Papers
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Journal ArticleDOI
TL;DR: In this article, the reducibility and characteristics of the supported copper oxide catalysts with various copper loadings were revealed and determined by temperature-programmed reduction (TPR) and electron paramagnetic resonance (EPR), respectively.

328 citations

Journal ArticleDOI
TL;DR: In this paper, temperature-programmed reduction (TPR) and X-ray diffraction (XRD) were used to characterize the catalysts of CuO/γ-Al2O3 catalysts.
Abstract: Yttria-doped ceria (YDC) and pure ceria (CeO2), respectively, were deposited on γ-alumina (γ-Al2O3) using the impregnation method; then, copper oxide was also supported on them by employing the impregnation method. For comparison, CuO/γ-Al2O3 catalysts were prepared in this work. The catalysts were characterized by temperature-programmed reduction (TPR) and X-ray diffraction (XRD). For CuO/γ-Al2O3 catalysts, two TPR peaks, namely β and γ, were observed. These have been attributed to the reduction of highly dispersed copper oxide species and bulk-like copper oxide, respectively. For CuO/CeO2/γ-Al2O3 and CuO/YDC/γ-Al2O3 catalysts, four TPR peaks, namely α1, α2, β′ and γ′, could be observed. The α peaks with lower peak temperatures as compared to those of β′ and γ′ peaks have been attributed to the reduction of interface-boundary copper oxide species that contact closely and interact strongly with the supported ceria or YDC. Crystal sizes calculated from XRD measurements confirmed that yttria (Y2O3) addition could lead to crystal growth of ceria and correspondingly enhance the dispersion of the supported copper oxide due to the partition of YDC crystallite. Hence, this work shows that supported YDC and ceria can act bi-functionally as a textural promoter as well as a structural promoter.

162 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, the kinetics and mechanism of CO oxidation on single and mixed oxides are examined, alongside the catalyst structures, in a review of the literature on carbon monoxide over oxide catalysts.
Abstract: Oxidation into CO2 is a major solution to CO abatement in air depollution treatments. The development of catalytic converters led to an extraordinary high number of publications on metal catalysts during the last fifty years. Due to the increasing price of noble metals and to remarkable progresses in oxide syntheses, catalytic oxidation of carbon monoxide over oxide catalysts has recently gained in interest, even if some oxides are known to present remarkable activity since the beginning of the 20th century. In this Review, the kinetics and mechanism of CO oxidation on single and mixed oxides are examined, alongside the catalyst structures

821 citations

Journal ArticleDOI
TL;DR: The results show the importance of kinetic effects for the formation of well-defined suboxides during a reduction process and the activation of oxide catalysts.
Abstract: Time-resolved X-ray diffraction, X-ray absorption fine structure, and first-principles density functional calculations were used to investigate the reaction of CuO and Cu(2)O with H(2) in detail. The mechanism for the reduction of CuO is complex, involving an induction period and the embedding of H into the bulk of the oxide. The in-situ experiments show that, under a normal supply of hydrogen, CuO reduces directly to metallic Cu without formation of an intermediate or suboxide (i.e., no Cu(4)O(3) or Cu(2)O). The reduction of CuO is easier than the reduction of Cu(2)O. The apparent activation energy for the reduction of CuO is about 14.5 kcal/mol, while the value is 27.4 kcal/mol for Cu(2)O. During the reduction of CuO, the system can reach metastable states (MS) and react with hydrogen instead of forming Cu(2)O. To see the formation of Cu(2)O, one has to limit the flow of hydrogen, slowing the rate of reduction to allow a MS --> Cu(2)O transformation. These results show the importance of kinetic effects for the formation of well-defined suboxides during a reduction process and the activation of oxide catalysts.

477 citations

Journal ArticleDOI
TL;DR: In this article, the authors showed that the CuO CeO 2 catalysts exhibit high catalytic activity in CO oxidation, showing markedly enhanced catalytic activities due to the combined effect of copper oxide and cerium dioxide.
Abstract: Copper oxide supported on cerium dioxide ( CuO CeO 2 ) catalysts were prepared and used for carbon monoxide oxidation in stoichiometric carbon monoxide and oxygen. The catalysts were characterized by means of XRD, H2-TPR and CO-TPD studies. The CuO CeO 2 catalysts exhibit high catalytic activity in CO oxidation, showing markedly enhanced catalytic activities due to the combined effect of copper oxide and cerium dioxide. The activity of the CuO CeO 2 (15%) catalyst prepared by impregnation is higher than that prepared by co-precipitation. CeO2 promotes the hydrogen reduction activity of copper, so that CuO CeO 2 catalysts show a different behavior with respect to pure CuO. Two reducible copper species were observed in all CuO CeO 2 catalysts. CO-TPD experiments revealed that CuO CeO 2 catalysts can adsorb CO, while pure CuO and CeO2 cannot. Combining the results of TPR, TPD study, and the catalytic activity measurements, it is proposed that the well dispersed CuO which can adsorb CO and which is reducible at low-temperature is responsible for low-temperature CO oxidation. The bulk CuO which cannot adsorb CO and which is reducible at high-temperature contributes little to the oxidation activity.

380 citations

Journal ArticleDOI
TL;DR: In this article, the reduction of CuO dispersed on fluorite-type oxide catalysts, namely La-doped CeO2 and Ydoped ZrO2, was studied.
Abstract: The reduction of CuO dispersed on fluorite-type oxide catalysts, namely La-doped CeO2 and Y-doped ZrO2 was studied in this work. On both supports distinct copper species were identified as a function of copper content by temperature-programmed reduction (TPR) by H2 and CH4, X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and scanning transmission electron microscopy/energy dispersive X-ray (STEM/EDX) analyses. At low copper loading ( 15 at%), in addition to clusters, larger CuO particles are present which are reduced at higher temperature close to the reduction temperature of bulk CuO. At copper loading lower than ca. 5 at%, copper is present as highly dispersed clusters or isolated Cu ions, which interact strongly with the fluorite-type oxide, thus requiring higher reduction temperature. However, the latter is still below the bulk CuO reduction temperature. Copper is more stabilized when dispersed in Ce(La)O2 than in Zr(Y)O2 matrix, so that reduction of copper oxide species requires lower temperatures on the Zr(Y)O2-based catalysts. The reducibility of the doped ceria is enhanced by the presence of copper in both H2- and CH4-TPR. On the other hand no such interaction is present in CuZr(Y)O2 system. The activity of various copper species for methane oxidation is discussed.

379 citations

Journal ArticleDOI
TL;DR: In this paper, a new series of CuZnAl(Zr)-oxide catalysts were prepared by the decomposition of hydrotalcite (HT)-like layered double hydroxide (LDH)/aurichal cite phases around 450°C, and physicochemical properties of the catalysts are investigated by X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS), temperature-programmed reduction (TPR), electron paramagnetic resonance (EPR) and surface area measurements.

333 citations