Ratio Of CuO Research Articles

The reactivity of CuO oxygen carrier and coal in Chemical-Looping with Oxygen Uncoupled (CLOU) and In-situ Gasification Chemical-Looping Combustion (iG-CLC)

Chemical-looping combustion (CLC) has the primary advantage of the generation of a CO2 enriched flue gas, which greatly benefits CO2 capture. Many researchers have been particularly interested in developing combined or mixed oxygen carriers (OC) to enhance and improve single metal OC properties. To advance the development of mixed OC, this study first focused on the conditions that impact the chemical reactions taking place in both In-situ Gasification Chemical-Looping Combustion (iG-CLC) and Chemical-Looping with Oxygen Uncoupled (CLOU) for single metal Cu based OC with coal and the gas product distributions. The Cu compounds present during CuO reduction (CuO→Cu2O→Cu) were also investigated using X-ray diffraction (XRD) as a function of carbon conversion during the reaction. In this study, the reactivity of char with CuO was tested at two different ratios of CuO to coal char (ϕ = 26 and 8) at 850 °C and 950 °C in Ar and Ar + H2O. Char conversion rates were greater at higher reaction temperatures (950 °C vs 850 °C) for all rests. At a high ratio of oxygen carrier to char (ϕ = 26), char was fully converted by reacting with O2 released from CuO at both 950 °C and 850 °C in Ar. CuO was reduced to Cu2O resulting from the thermal release of gaseous oxygen. At a low ratio of oxygen carrier to char under Ar + H2O (ϕ = 8), char was fully converted at both 950 °C and 850 °C by char combustion with O2 from the OC and syngas CLC from char-H2O gasification. Additionally, CuO was reduced to metallic Cu. IG-CLC had a lower CO2 capture efficiency with CO in the product gas and a lower carbon conversion rate compared to CLOU. From a reactivity view point, CLOU is a promising process for coal chemical-looping combustion.

Synthesis, Characterization, and Optical Properties of Near-Infrared Reflecting Composite Inorganic Pigments Composed of TiO2/CuO Core–Shell Particles

Pigments with dark appearance and high solar energy reflectance are of great application value. In the present work, dark grey composite pigments with a TiO2/CuO core–shell structure were prepared through calcination of precursors obtained from the precipitation of Cu(OH)2 on TiO2 particles. The composition, structure, and optical properties of the synthesised powders were characterised by colourimetry, near-infrared diffuse reflectance spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The pigments are composed of rutile TiO2 and tenorite CuO, and the powder colour changes from white to dark grey as the Cu content increases. With a molar ratio of CuO to TiO2 of 0.6, the pigment presents optimal colour (a* = 1.66, b* = −2.19, L* = 52.37) and optical performance. The near-infrared reflectance, the solar reflectance in the near-infrared region, and the total solar reflectance reach 87.2, 70.6, and 37.2 %, respectively. Furthermore, it is demonstrated that the composite pigments exhibit a deeper colour and higher reflectivity than conventional dark-blended powders. These cool dark pigments could be applied in the coatings for buildings (roofs and walls) to improve building comfortability and reduce cooling energy consumption.

Outstanding gas sensing performance of CuO-CNTs nanocomposite based on asymmetrical schottky junctions

Abstract To fabricate a high-performance material for sensor devices at room temperature and further improve the synthetic approach of sensing materials, one dimensional (1D) CuO-CNTs nanocomposites were prepared with CNTs and CuO nanorods (NRs) via a facile reflux method. The 1D composite with the molar ratio of CuO and CNTs at 2.4:1 displays excellent gas sensing performance, i.e. the lowest detectable limit of 970 ppb and the short response time of 6 s–97.0 ppm NO2 at room temperature. In the 1D composite, the CNTs part provides a channel to enable effective and fast carrier transport, while the CuO NRs fabricates an asymmetrical schottky contact at the interface between the composites and the Au electrode. The advantage of the synergy of CNTs and CuO which possesses superior conductivity benefits the sensing of our 1D CuO-CNTs composite by providing affluent electrons.

Aqueous-phase electrochemical reduction of CO2 based on SnO2[sbnd]CuO nanocomposites with improved catalytic activity and selectivity

In the present study we demonstrate that the activity and selectivity of SnO2 nanocatalysts during the aqueous-phase electrochemical reduction CO2 can be effectively tailored by coupling of nanostructured CuO to form SnO2CuO nanocomposites. Comparing the Faradaic selectivity of formate as a function of the applied electrode potential and electrolysis time, it is found that CuO incorporation can significantly improve the activity of SnO2CuO composite catalysts. When the ratio of CuO in the bulk composite was 50%, the formed SnO2(50%)-CuO(50%) nanocomposite gives the best catalytic performance with the onset potential as early as −0.75 V and the current density at −1.25 V as high as about −24 mA cm−2. Ion chromatography measurement demonstrates that when the electrolysis was held at −1.0 V for 1 h in 0.5 M KHCO3, the maximum Faradaic efficiency of formate production can be high up to 74.1%. The outstanding stability of SnO2 nanocatalyst fabricated electrode is also evidenced due to the stronger synergistic effect induced by CuO compositing, where the SnO2(50%)-CuO(50%) composite catalyst keeps a steady current density without any dropt over 30 h’ continuous electrolysis approach. The improved performances are deduced from the strong synergistic interactions between SnO2 and CuO nanocomposite as evidenced from SEM, XRD and XPS analysis results.

Efficient bimetallic NiCu-SiO2 catalysts for selective hydrogenolysis of xylitol to ethylene glycol and propylene glycol

The selective hydrogenolysis of biomass-derived xylitol to ethylene glycol and propylene glycol was carried out over non-noble Ni-decorated Cu-SiO2 nanocatalysts with a wide range of Cu/Ni mass ratios and metal loadings in the presence of Ca(OH)2. The NiCu-SiO2 bimetallic catalysts showed much superior activities and selectivities to the target glycols relative to the monometallic Cu-SiO2 and Ni-SiO2 catalysts. Among them, 10Ni80Cu-SiO2 catalyst (10/80 refers to the mass ratio of NiO and CuO) prepared by co-precipitation-gel method presented the highest activity and target glycols selectivity, and up to 81.0% combined glycol yield was attained at 473K and 8MPa H2. Moreover, this catalyst exhibited greatly enhanced stability in repeated runs. Characterization of these catalysts by XRD, XPS, BET, N2O-chemisorption, H2-TPR and TEM showed that the decoration of suitable amount of Ni into Cu-SiO2 catalysts had favorable effects on Cu dispersion, catalyst reducibility and the formation of highly active Ni surface-enriched Cu-Ni alloy sites. The notably enhanced performances of the NiCu-SiO2 bimetallic catalysts could be ascribed to their significantly promoted C–OH dehydrogenation and C=O hydrogenation activities and high resistance to sintering of the active sites, imposed by the structural and electronic effects of Ni. Clearly, these findings provide useful guidance for the design of more efficient and stable non-noble bimetallic nanocatalysts for upgrading biomass-derived platform compounds particularly via hydrogenation/hydrogenolysis reactions.

Creating an Optimal Microenvironment within Mesoporous Silica MCM-41 for Capture of Tobacco-Specific Nitrosamines in Solution.

To meet the requirement of capturing tobacco-specific nitrosamines (TSNA) for environment protection, a unique microenvironment was carefully created inside the channels of mesoporous silica MCM-41. In situ carbonization of template micelles at 923 K, combined with the excess aluminum used in one-pot synthesis of MCM-41, is adopted to tailor the tortuosity of mecsoporous channels, while loaded metal oxides (5 wt %) and the Al component in the framework are employed to exert the necessary electrostatic interaction toward the target carcinogens TSNA in solution. The elaborated microenvironment created in mesoporous sorbents was characterized with XRD, N2 adsorption-desorption, TEM, XPS, and TG-DSC methods. Various solutions of Burley- and Virginia-type tobaccos were used to assess the adsorption performance of new mesoporous sorbents, and the influence of the solid-to-liquid ratio, adsorption time, and loading amount of CuO on the adsorption was carefully examined. The representative sample 5%Cu/AM-10c could capture 27.2% of TSNA in Burley tobacco solution, and its capacity reached 0.3 mg g-1 in Snus tobacco extract solution, offering a promising candidate for the protection of the environment and public health.

Copper-based oxygen carriers supported with alumina/lime for the chemical looping conversion of gaseous fuels

Copper (II) oxide in varying ratios was combined with either an alumina-based cement (Al300), or CaO derived from limestone as support material in a mechanical pelletiser. This production method was used to investigate its influence on possible mechanical and chemical improvements for oxygen carriers in chemical looping processes. These materials were tested in a lab-scale fluidised bed with CO or CH4 as a reducing gas at 950 °C. As expected, the oxygen carriers containing a greater ratio of support material exhibited an enhanced crushing strength. Oxygen carriers comprised of a 1:3 ratio of support material to active CuO exhibited increased crushing strength by a minimum of 280% compared to pure CuO pellets. All oxygen carriers exhibited a high CO conversion yield and were fully reducible from CuO to Cu. For the initial redox cycle, Al300-supported oxygen carriers showed the highest fuel and oxygen carrier conversion. The general trend observed was a decline in conversion with an increasing number of redox cycles. In the case of CaO-supported oxygen carriers, all but one of the oxygen carriers suffered agglomeration. The agglomeration was more severe in carriers with higher ratios of CuO. Oxygen carrier Cu25Al75 (75 wt% aluminate cement and 25 wt% CuO), which did not suffer from agglomeration, showed the highest attrition with a loss of approximately 8% of its initial mass over 25 redox cycles. The reducibility of the oxygen carriers was limited with CH4 in comparison to CO. CH4 conversion were 15%–25% and 50% for Cu25Ca75 (25 wt% CuO and 75 wt% CaO) and Cu25Al75, respectively. Cu25Ca75 demonstrated improved conversion, whereas Cu25Al75 exhibited a trending decrease in conversion with increasing redox cycles.

Three-dimensionally ordered macroporous metal oxide–silica composite for removal of mercaptan

A series of 3DOM and non-3DOM metal oxide–silica composites were prepared and tested dynamically in a packed-bed reactor at room temperature to remove ethanethiol from a gas stream containing ethyl mercaptan in moist N2.The obtained sorbents were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption–desorption techniques. The experimental results showed that the adsorption ability of different kinds of metal oxide–silica composites with 3DOM structure decreased in the sequence: 3D-CuO/SiO2 > 3D-NiO/SiO2 > 3D-Co3O4/SiO2 > 3D-ZnO/SiO2. The best ratio of CuO to SiO2 of 3DOM copper–silicon oxide sorbents for ethanethiol removal was found to be 1:2. The 3DOM structure could improve the removal activity of sorbents remarkably because of the high porosity with ordered interconnected macropores as well as the large surface area and high dispersion of CuO. It was also found that a moist atmosphere greatly benefited the adsorption of ethanethiol at ambient condition.

Highly Efficient and Recyclable g-C3N4/CuO Hybrid Nanocomposite Towards Enhanced Visible-Light Photocatalytic Performance

A highly efficient visible-light-driven g-C3N4/CuO hybrid nanocomposite catalyst with different molar contents of CuO are successfully fabricated via a simple liquid phase synthesis process and applied to the degradation of Rhodamine B (RhB) solution. The results reveal that monodisperse CuO nanoparticles with a size of less than 10[Formula: see text]nm are uniformly distributed on the surface of g-C3N4nanosheets. Compared with the pure g-C3N4and CuO, the as-prepared nanocomposite displays significantly enhanced photocatalytic performance under visible-light irradiation. Attractively, the photocatalytic activities of the nanocomposite catalysts can be tuned by adjusting the molar ratio of g-C3N4and CuO. When the molar ratio reaches 2:1, the nanocomposite exhibits the highest photocatalytic activity, which can decompose RhB completely in 5[Formula: see text]min. The improved performance could be ascribed to the formation of heterostructure between g-C3N4and CuO as well as the decreased particle size of CuO, the presence of H2O2, large surface-exposure area and the suitable band position of g-C3N4/CuO nanocomposite. Interestingly, the nanocomposite shows excellent stability and recyclable property toward the photodegradation of RhB. Finally, a possible photocatalytic mechanism is proposed.

Combustion performance of sewage sludge in chemical looping combustion with bimetallic Cu–Fe oxygen carrier

Sewage sludge is the by-product from the wastewater treatment plant. It can be utilized by chemical looping combustion (CLC) for energy conversion and phosphorus recovery. Hematite is an attractive material for CLC due to its abundance, low cost and environmental compatibility. However, hematite shows low reactivity for CLC of solid fuel. The reactivity of hematite can be improved by synthesizing with CuO. This work is to evaluate the combustion performance and NO emission in CLC of sewage sludge in a batch fluidized-bed reactor. The oxygen carrier materials consisted of a mixture of hematite and CuO, which were synthesized using mechanical mixing method. The effect of reduction temperature and the CuO/hematite mass ratio on combustion efficiency and NO emission were investigated. The results show that the mixture of CuO and hematite can give significant improvement in sludge conversion in comparison to only hematite. The oxygen carrier which consisted of 40% CuO and 60% hematite gave the highest sludge conversion with or without steam in fluidizing gas. Most of the nitrogen in sewage sludge was released as N2 during the reduction period. About 0.4% of N in sewage sludge was converted to NO using the materials containing 10% CuO and 90% hematite. The conversion of fuel-N to NO decreased with the mass ratio of CuO/(CuO+hematite) from 10% to 40%. Additionally, the structural and morphological stability of the oxygen carriers have been examined. The formation of CuFe2O4 could improve both the reactivity of Fe2O3 species through synergetic effect and the physical stability of CuO during redox reactions. Therefore, mixing hematite with CuO could be suitable for CLC of sewage sludge.

Spectral characterization of mechanically synthesized MoO3-CuO nanocomposite

In this work, MoO3-CuO metal oxide composite nanopowders are prepared by simple mechanochemical assisted synthesis technique with the stoichiometric weight ratios of MoO3 and CuO as 2.3:1 and 3.3:1, respectively. The structural and spectroscopic properties of the as-synthesised samples are characterised by XRD, SEM with EDS, FT-IR, Raman spectroscopy and TGA/DTA. X-ray diffraction pattern demonstrates the peaks correspond to orthorhombic phase of α-MoO3 and monoclinic phase of β-CuO. The average crystalline sizes of the 2.3:1 and 3.3:1 samples were found to be 16 and 24 nm, respectively, which are supported by Williamson–Hall (W–H) calculations. The correlations between the milling rotational speeds with morphological characteristics are revealed by the SEM images. The fundamental modes of Mo=O and Cu–O were analysed by FT-IR. Raman analysis has provided the qualitative information about the structure of the mixed oxide composite. Thermogravimetry analysis and Differential Thermal Analysis (DTA) of MoO3-CuO have revealed that the dual phase mixed oxide composite is stable up to 709 °C with a negligible weight loss. Based on the above, it can be inferred that the synthesised mixed lubricous oxide nanocomposite could be used as a solid lubricant at elevated temperatures.

Influence of calcination temperature on CuO–CeO2/SiC catalysts for SO3 decomposition in the sulfur–iodine cycle for hydrogen production

The copper-cerium composite oxides supported on silicon carbide (SiC) catalysts (CuO–CeO2/SiC) for sulfuric acid decomposition were studied in sulfur-iodine (SI or IS) cycle. The influence of calcination temperatures (800 °C–1000 °C) of CuO–CeO2/SiC catalysts on their activities and morphology were investigated in this study. The activity of CuO–CeO2/SiC was prominently higher than that of CuO–CeO2 composite oxides catalyst. The SO3 conversion ratio of CuO–CeO2/SiC catalyst increased with calcination temperature from 800 °C to 900 °C, while decreased with calcination temperature at 900 °C–1000 °C. XRD pattern, TEM (HRTEM) images and Energy Dispersive X-ray (EDX) spectra revealed that copper–cerium composite oxides were well dispersed and immobilized on the surface of SiC grains. XRD pattern showed that the accelerated transformation of SiC crystals to amorphous SiO2 and the rapid expansion of CeO2 sub-grains at the calcination temperature of 900 °C–1000 °C, as well as the accelerated amorphization of CuO crystals at 800 °C–900 °C. The agglomeration of catalysts with sintering temperature was also proven by the BET test. At a higher calcination temperature, X-ray photoelectron spectroscopy (XPS) of Cu2p spectra revealed the reduction of more Cu2+ in the process of SiC oxidation. According to TEM (HRTEM), XPS, and infrared radiation, the amorphous SiO2 was produced by the oxidation of superficial SiC particles, and the thickness of the SiO2 layers on SiC grains increased with the calcination temperature. A simple mechanism depicted the oxidation of CuO–CeO2/SiC was created.

Replacement of P3HT and PCBM with metal oxides nanoparticles in inverted hybrid organic solar cells

Inverted hybrid organic solar cells based on pairs of donor and acceptor materials offer an enhanced light absorption width and charge collection. Although recent developments lead to a demonstrated power conversion efficiency (PCE) of over 4% for such devices; basic underlying phenomena are still under investigation. In order to understand role of introducing nanoparticles in inverted hybrid solar cells, devices with various weight ratios of P3HT, CuO, PCBM and ZnO were prepared. The addition of CuO and ZnO improved the PCE of the P3HT:PCBM solar cells. The incorporation of nanoparticles were found to enhance the absorption and also increase the surface roughness of the active layer. The CuO and ZnO nanoparticles agglomerated as their ratio relative to P3HT and PCBM increased and completely aggregated in the absence of conjugated polymer and fullerene derivative.

Self-template synthesis of CuO@Cu3(BTC)2 composite and its application in cumene oxidation

CuO@Cu3(BTC)2 composite (BTC=benzene-1,3,5-tricarboxylate) was synthesized via a facile self-template method using CuO as the precursor. Cu3(BTC)2 is a representative MOF (metal-organic framework), which is a class of crystalline inorganic–organic hybrid materials. By controlling synthesis time, CuO@Cu3(BTC)2 with different content of Cu3(BTC)2 was obtained. The products were characterized by X-ray diffraction (XRD), thermogravimetric (TG) analysis, transmission electron microscopy (TEM) and N2 sorption measurement. It suggested that when controlling longer synthesis time, CuO@Cu3(BTC)2 contained more Cu3(BTC)2 and showed larger surface area and total pore volume. CuO@Cu3(BTC)2 can effectively catalyze oxidation of cumene to cumene hydroperoxide (CHP) and the yield of CHP reached 18.1%, which was better than 13.6% by CuO or 8.7% by Cu3(BTC)2. When the ratio of CuO:Cu3(BTC)2 in CuO@Cu3(BTC)2 was 1:0.073 and 1:0.115, CHP yield was 18.1% and 14.2%, respectively. This study provides an approach for the oxidation of alkyl benzene using metal-oxide@MOF composite as catalyst.

Magnetic Composite Fe<sub>3</sub>O<sub>4</sub>/CuO/TiO<sub>2</sub> Nanoparticles: Preparation, Characterization and Photocatalytic Activity

Magnetic composite Fe3O4/TiO2/CuO nanoparticles have been synthesized by sol-gel method at low temperature. The resultant composite nanoparticles coupled with different Cu contained by adjusting the molar ratio of CuO to (Fe3O4/TiO2) from 1:1 – 5:1. The structure, morphology and properties of nanoparticles were characterized using XRD, EDX, FESEM and VSM. The results showed that all composite nanoparticles consist of cubic spinel Fe3O4, anatase TiO2 and monoclinic CuO, have ferromagnetic properties. The photocatalytic performance was evaluated using methylene blue in aqueous solutions under UV and visible light irradiation. Among the composite Fe3O4/TiO2/CuO nanoparticles, the sample with the molar ratio of CuO to (Fe3O4/TiO2) = 5 : 1 exhibited the highest photocatalytic efficiency. Photocatalytic mechanism was investigated by measuring the photocatalytic degradation rate in the presence of scavenger. The results suggested that holes play the most important role in degradation of methylene blue.

Multi Level Operation of CuO Based Cbram with Cute Electrode

Conducting Bridge Random Access Memory (CBRAM) is a one of the most promising new memories due to its simple structure, low power consumption, high scaling potential, large on/off margin and high speed. It has been known that resistivity switching mechanism of CBRAM is induced by filament formation and rupture due to metal cation movement in the solid electrolyte. Typically CBRAM has capacitor like structure that a solid electrolyte is inserted between two metal electrodes. One electrode must be reactive metal and the other must be inert. Ag and Cu have been mainly used for a reactive electrode in CBRAM due to high field-induced-diffusivity of ion in the solid electrolyte. Such a reactive metal acts as an ion supplying source to form metal filament in solid electrolyte. In some cases, since too strong filament was formed in the solid electrolyte due to high field-induced-diffusivity of ion causing a reset stuck, it is hard to control filament formation and rupture. Although many studies on CBRAM have been carried out, there are only a few studies on controlling filament. Therefore we investigated how the filament formation is controlled with CuTe electrode and demonstrated muiti level operation of CuO based CBRAM with CuTe electrodes. In particular, we compared CuTe with Cu electrodes to understand the role of Te in CuO based CBRAM with CuTe electrode. Fig.1 shows that CuO based CBRAM structure and I-V curves with Cu and CuTe electrode, respectively. In case of Cu electrode, reset stuck occurs at operation condition with high compliance current (10-3A) while switching behavior appears at operation condition with low compliance current, as shown in Fig.1 (b). On the other hand, CuO based CBRAM with CuTe electrode shows stable switching behavior at operation condition with low compliance current and even at the high compliance current, as shown in Fig.1 (e). In case of Cu electrode, it was expected that too strong and thick filament was formed in the CuO solid electrolyte at operation condition with high compliance current. On the other hand, partially localized thin-filament is formed in case of CuTe electrode so that, Te acts as diffusion barrier of Cu. In addition, On/Off ratio of CuO based CBRAM with CuTe electrode was bigger than that of Cu electrode so that, HRS (High Resistive State) of the CuO based CBRAM with CuTe electrode was lower than that of the CuO based CBRAM with Cu electrode. These results indicate that CuO based CBRAM with CuTe electrode showed superior properties in MLC. CuO CBRAM with CuTe electrode shows retention time 5x104sec, DC program/erase cycles of 102, and memory margin (Ion/Ioff) higher than 103 with four different state, as shown Fig. 2. In the conference meeting, we present switching characteristics at high compliance current in CuO based CBRAM by using CuTe electrode and discuss Multi Level Cell (MLC) operation by varying compliance current. * This work was financially supported by the Industrial Strategic Technology Development Program (10039191, The Next Generation MLC PRAM, 3D ReRAM, Device, Materials and Micro Fabrication Technology Development) funded by the Ministry of Trade, Industry and Energy (MOTIE), Republic of Korea and the Brain Korea 21 Plus, Republic of Korea. Reference [1] Juarez L. F. Da Silva et al, Stability and electronic structures of CuxTe, Applied Physics Letters 91, 091902 (2007) [2] L. Goux et al, Influence of the Cu-Te composition and microstructure on the resistive switching of CuTe/Al2O3/Si cells, Applied Physics Letters 99, 053502 (2011) Figure 1

Characteristics of Copper-based Oxygen Carriers Supported on Calcium Aluminates for Chemical-Looping Combustion with Oxygen Uncoupling (CLOU)

Eight different oxygen carriers (OC) containing CuO (60 wt %) and different mass ratios of CaO to Al2O3 as the support were synthesized by wet-mixing followed by calcination at 1000 °C. The method of synthesis used involved the formation of calcium aluminum hydrate phases and ensured homogeneous mixing of the Ca2+ and Al3+ ions in the support at the molecular level. The performance of the OCs for up to 100 cycles of reduction and oxidation was evaluated in both a thermogravimetric analyzer (TGA) and a fluidized bed reactor, covering a temperature range of 800 to 950 °C. In these cycling experiments, complete conversion of the OC, from CuO to Cu and vice versa, was always achieved for all OCs. The reactivity of the materials was so high that no deactivation could be observed in the TGA, owing to mass transfer limitations. It was found that OCs prepared with a mass ratio of CaO to Al2O3 in the support >0.55 agglomerated in the fluidized bed, resulting in an apparent deactivation over 25 cycles for all tempe...

In-situ DRIFTS and XANES identification of copper species in the ternary composite oxide catalysts CuMnCeO during CO preferential oxidation

A series of CuMnCeO catalysts with 10% CuO (weight loading) and variable atomic ratios of Mn/Mn + Ce (0, 0.02, 0.05 or 0.10) were synthesized by co-precipitation and employed for CO preferential oxidation (CO PROX). After doping a small amount of manganese into ceria, the catalysts show improved catalytic performance as compared with the undoped one, especially the catalyst with the Mn/Mn + Ce atomic ratio of 0.05 (CMC-0.05) which displays the lowest temperatures for half CO conversion (T50 = 73 °C) and full CO conversion (T100 = 108 °C). In addition, it also exhibits the widest temperature window of full CO conversion (108–149 °C) and 100% selectivity of oxygen to CO2 below 117 °C. As revealed by XRD and UV-Raman, the presence of appropriate amount of Mn cannot only enhance the formation of Ce–Cu–Mn–O ternary oxide solid solution with fluorite structure, inhibiting the growth of CeO2 crystallite size, but also increase the oxygen vacancies. The results of H2-TPR and XPS indicate that the reducibility and amount of surface oxygen species of CMC-0.05 are also improved, both of which are beneficial to catalytic performance. In situ XANES results suggest that the bulk copper species still remain as Cu2+ ions below 200 °C even in H2-rich CO PROX atmosphere; however, the in-situ DRIFTS spectra indicate that during CO PROX below 120 °C the surface copper species are Cu+ ions which are regarded as the main active sites for CO PROX; above 120 °C Cu0 species appear, which enhance H2 oxidation, decreasing the oxygen to CO2 selectivity.

Corrosion behaviour of copper in LiBr solutions – surface examination

Optical microscope (O.M) and scanning electron microscope (SEM) equipped with energy dispersive X‐ray (EDX) were used to follow the changes that occurred on the surfaces of copper after treated electrochemically in concentrated solutions of LiBr (up to 9 M). Results showed the existence of protective film of CuO and Cu(OH)2 which are recorded during the passive film formation in 5 × 10–1 M LiBr at 200 mV. At 1 M LiBr and during the partial passive region (600 mV) a porous film of Cu2O with a small ratio of CuOH and Cu(OH)2 were detected which confirmed the higher current density recorded. On the other hand and at the same concentration (1 M LiBr at 1000 mV), surface examination confirmed the detection of CuBr2 with small ratio of CuO which explain the deleterious effect of bromide and the autocatalytic dissolution of Cu at this higher potential. At higher concentrations from 4 to 9 M, the film formed is non homogeneous with a more porous structure which is mainly CuBr and some area of the film suffered from cracking. This proves the general dissolution through the complexing formation of soluble CuBr2–.

NH3 Oxidation Mechanism over Cu/SAPO‐34 Catalysts Prepared by Different Methods

AbstractNH3 oxidation mechanism and its inhibition effect on the selective catalytic reduction of NOx by NH3 (NH3–SCR) reaction over two series of Cu/SAPO‐34 catalysts were studied. It was found that the different NO conversions were induced by the diverse NH3 oxidation degree. X‐ray diffraction, scanning electron microscopy, H2 temperature‐programmed reduction (H2–TPR), and CO diffuse reflectance infrared Fourier transform spectroscopy (CO–DRIFTS) analyses were conducted to estimate the Cu species distribution. The TPR results showed that the CuO species was dominant in impregnated Cu/SAPO‐34 samples, and the ion‐exchanged Cu/SAPO‐34 samples contained more isolated Cu2+ species. Furthermore, H2–TPR, electron paramagnetic resonance, and CO–DRIFTS analyses were utilized to quantify the CuO, Cu2+, and Cu+ species. The results together with the kinetic results revealed the CuO is the active site for NH3 oxidation, and the NH3 oxidation over Cu/SAPO‐34 sample consists two steps: (a) NO production; (b) further NO consumption by adsorbed NH3 species on Cu2+ sites. Finally, the inhibition of NH3 oxidation on NH3–SCR activity was explained and the NO conversion at high temperature was related to the Cu2+/CuO ratio in Cu/SAPO‐34 sample.