Catalytic Performance Of Cu Research Articles

Cu(II)Cu(I)/AC Catalysts for Gas–Solid Acetylene Dimerization

Cu(II)Cu(I)/activated carbon (AC) catalysts with different copper chloride and cuprous chloride impregnation orders were firstly prepared. The effect of the Cu(II) additive on the catalytic performance of Cu(I)/AC catalysts for gas-solid acetylene dimerization was assessed, and the catalysts were characterized using XRD, TEM, TPR, TPD, TGA, BET, XPS and ICP-AES. The optimal catalytic performance is obtained using the Cu(II)0.3Cu(I)1/AC catalyst with an average acetylene conversion of 70.0% (reaction conditions: temperature: 100°C; acetylene gas hourly space velocity: 120 h-1). This value is an increase of 33.0% compared with the average acetylene conversion of 37.0% when the Cu(I)1/AC catalyst is used under the same reaction conditions. The results demonstrated that the addition of Cu(II) promoted the dispersion of the active components, inhibited copper loss on the catalysts, and enhanced the adsorption of reactant acetylene on the catalysts. Consequently, the results indicate that a suitable Cu+/Cu2+ mo...

Effect of Transition Metal Additives on the Catalytic Performance of Cu–Mn/SAPO-34 for Selective Catalytic Reduction of NO with NH3 at Low Temperature

The adsorption of NO, NH3, H2O, and SO2 gaseous molecules on different transition metal oxides was studied based on density function theory (DFT), and three better-performing transition metal elements (Fe, Co, and Ce) were selected. Cu–Mn/SAPO-34 catalysts were prepared by impregnation method and then modified by the selected transition metals (Fe, Co, and Ce); the SO2 resistance experiments and characterizations including Brunner−Emmet−Teller (BET), X-ray Diffraction (XRD), Scanning Electronic Microscopy (SEM), and thermal gravity analysis (TG)-differential thermal gravity (DTG) before and after SO2 poisoning were conducted. The results showed that the deactivation of the Cu–Mn/SAPO-34 catalyst is ascribed to the deposition of lots of ammonium sulfates on the surface, depositing on the active sites and inhibiting the adsorption of NH3. After the modification of Fe, Co, and Ce oxides, the SO2 resistance of the modified Cu–Mn/SAPO-34 catalyst was significantly enhanced due to the less formation of ammonium sulfates. Among all these modified Cu–Mn/SAPO-34 catalysts, the Cu–Mn–Ce/SAPO-34 exhibited the highest SO2 resistance owing to the decreased decomposition temperature and the trapper of ceria for capturing SO2 to form Ce(SO4)2, further inhibiting the deposition of ammonium sulfates.

Cu(5%)/Al2O3 catalytic performance on the phenol wet oxidation with H2O2: Influence of the calcination temperature

In this work the catalytic performance of Cu(5%)/Al2O3 catalysts prepared by wet impregnation and calcined at three different temperatures, 400 °C (WI 400), 650 °C (WI 650) and 900 °C (WI 900), was analyzed. These materials were tested in the phenol wet oxidation reaction using H2O2 (0.22 or 0.88 M) as an oxidizing agent, 1000 mg/L of phenol at 70 °C and atmospheric pressure. A complete conversion of phenol and a high extent of phenol mineralization were obtained for the three catalysts. Surface Cu2+ species suffered a reduction process during the catalytic reaction due to the drop of the pH value and a fraction of the reduced copper was leached to the liquid phase. Despite this, the increment in the calcination temperature produced a decrease in this reduction extent, inducing a protective effect to the Cu2+ species through the interaction between these and the support. Moreover, the existence of Cu-Al-O interactions not only diminished Cu2+ species reduction but also their leaching. Even though the WI 900 catalyst presented the lower leaching extent (36%), the remaining amount of copper in the solution still exceeded the allowed limit value for drinking water (1 mg Cu/L).

Exploring the ternary interactions in Cu\u2013ZnO\u2013ZrO2 catalysts for efficient CO2 hydrogenation to methanol

The synergistic interaction among different components in complex catalysts is one of the crucial factors in determining catalytic performance. Here we report the interactions among the three components in controlling the catalytic performance of Cu–ZnO–ZrO2 (CZZ) catalyst for CO2 hydrogenation to methanol. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements under the activity test pressure (3 MPa) reveal that the CO2 hydrogenation to methanol on the CZZ catalysts follows the formate pathway. Density functional theory (DFT) calculations agree with the in situ DRIFTS measurements, showing that the ZnO–ZrO2 interfaces are the active sites for CO2 adsorption and conversion, while the presence of metallic Cu is also necessary to facilitate H2 dissociation and to provide hydrogen resource. The combined experiment and DFT results reveal that tuning the interaction between ZnO and ZrO2 can be considered as another important factor for designing high performance catalysts for methanol generation from CO2.

Catalytic performance of Cu- and Zr-modified beta zeolite catalysts in the methylation of 2-methylnaphthalene

2,6-Dimethylnaphthalene (2,6-DMN) is a commercially important chemical for the production of polyethylenenaphthalate and polybutylene naphthalate. However, its complex synthesis procedure and high production cost significantly reduce the use of 2,6-DMN. In this study, the synthesis of 2,6-DMN was investigated with methylation of 2-methylnaphthalene (2-MN) over metal-loaded beta zeolite catalysts including beta zeolite, Cu-impregnated beta zeolite and Zr-impregnated beta zeolite. The experiments were performed in a fixed-bed reactor at atmospheric pressure under a nitrogen atmosphere. The reactor was operated at a temperature range of 400–500 °C and varying weight hourly space velocity between 1 and 3 h−1. The results demonstrated that 2,6-DMN can be synthesized by methylation of 2-MN over beta type zeolite catalysts. Besides 2,6-DMN, the product stream also contained other DMN isomers such as 2,7-DMN, 1,3-DMN, 1,2-DMN and 2,3-DMN. The activity and selectivity of beta zeolite catalyst were remarkably enhanced by Zr impregnation, whereas Cu modification of beta zeolite catalyst had an insignificant effect on its selectivity. The highest conversion of 2-MN reached 81%, the highest ratio of 2,6-DMN/2,7-DMN reached 2.6 and the highest selectivity of 2,6-DMN was found to be 20% by using Zr-modified beta zeolite catalyst.

Comprehensive theoretical analysis of the influence of surface alloying by zinc on the catalytic performance of Cu(1 1 0) for the production of methanol from CO2 selective hydrogenation: Part 1 – Thermochemical aspects

Open copper facets such as Cu(1 1 0) were recently reported to most likely act as an active center of commercial Cu/ZnO/Al2O3 methanol synthesis catalysts. Surprisingly, unlike other surfaces of the metal component, the Cu(1 1 0) facet suffers from severe deactivation by deposited reduced zinc adatoms under catalyst working conditions. Elucidating the catalytic behavior of the novel reactive site and the Zn poisoning effect in detail is highly desirable, however, very challenging. As the first paper of a series devoted to tackle these intriguing issues, we have performed density functional calculations and atomistic thermodynamic modeling to examine the mechanism of CO2 hydrogenation on a CuZn(1 1 0) surface alloy and, as a reference, its parent Cu(1 1 0) substrate. Based on the obtained formation free energies, guest Zn atoms were predicted to be enriched on the uppermost layer of CuZn(1 1 0), preferentially leading to Cu-based single-atom alloys. According to the computations of the authors, the methanol production on the two systems may proceed via formate (HCOO*) rather than both the CO* and carboxyl (HOCO*) species, laying pivotal foundations for future kinetic analysis. The structural insensitivity of the production process is traced back to slight improvement of the stability of most reaction intermediates by partial surface alloying. More in detail, there exist several thermodynamically viable intermediate-mediated strategies that convert bidentate HCOO* to another precursor formaldehyde (H2CO*), that is, bi-HCOO* → dioxymethylene (H2COO*) → hydroxymethoxy (H2COOH*) → H2CO*, bi-HCOO* → formic acid (HCOOH*) → H2COOH* → H2CO*, and bi-HCOO* → HCOOH* → formyl (HCO*) → H2CO*. Under the assistance of the semiempirical Brönsted–Evans–Polanyi (BEP) principle and previous published works, comparison of reaction free-energy data for key elemecntary steps indicates that on CuZn(1 1 0) and Cu(1 1 0), the rate-limting step of methanol synthesis is H3CO* hydrogeantion. Moreover, the Zn-contaminated surface renders the H3CO* + H* reaction thermodynamically and kinetically less favorable than on the latter one, which thus inhibits CO2 hydrogenation to H3COH. In summary, our finding is applicable in explaining the catalytic performance variation when Cu(1 1 0) is alloyed with Zn atoms.

Influence of impregnated copper and zinc on the pyrolysis of rice husk in a micro-fluidized bed reactor: Characterization and kinetics

Catalytic performance of Cu and Zn catalysts was investigated during rice husk (RH) high-temperature pyrolysis under isothermal conditions in a micro-fluidized bed reactor. The results showed that the presence of Cu and Zn evidently influenced the release characteristics and conversion of the gas components. The impregnated Cu promoted the conversion of H2, CH4, CO and CO2, while Zn showed positive catalytic effect on the conversion of H2, CH4 and CO2 and negative effect on the conversion of CO. The X-ray diffraction patterns of the residue chars revealed that metallic copper nanoparticles (Cu0) were formed during Cu impregnated biomass pyrolysis. Textural characterization and SEM images showed that the impregnation of Cu and Zn, particularly Zn, promoted the generation of micropores and mesopores, with the pore sizes predominantly at around 1.3 nm and 3.9 nm. Reaction kinetics for generating these gases was studied based on model fitting method, and the most probable reaction mechanism was obtained based on the relative error between experimental and calculated conversion data. The resulting apparent activation energies were 85.08, 12.56, 49.72 and 38.37 kJ/mol for the formation of H2, CO, CH4 and CO2 from pure RH pyrolysis. The presence of Cu decreased the forming activation energies of the four gases, and Zn decrease the forming activation energies of H2, CH4 and CO2 while increased the value for the formation of CO.

Preparation, Structural Characteristics, and Catalytic Performance of Cu–Co Alloy Supported on Mn–Al Oxide for Higher Alcohol Synthesis via Syngas

A series of Mn–Al oxide supported Cu–Co alloy catalysts having various molar ratios of Cu/Co were prepared using the facile sol–gel synthesis, with the aim of investigating the effects of the chemical, physical properties in the catalytic behavior on higher alcohol synthesis (HAS). The as-prepared samples were characterized through utilizing XRD, BET, TEM, XPS, H2-TPD/TPR, CO-TPD, in-situ CO adsorption DRIFTS, and CO-TPSR techniques. The study suggests that the proper ratio of Cu/Co could adjust the amount of adsorbed hydrogen and nondissociatively adsorbed CO at the surface of catalyst on CO hydrogenation and insertion, improve the reducibility, and ameliorate the catalytic behavior for HAS. Especially, the 3Cu–5Co/(Mn–Al) catalyst showed the best catalytic behavior with a CO conversion of 33.4%, total alcohol selectivity of 39.7%, C2+ alcohol selectivity in the total alcohols of 57.3% at GHSV of 5000 h–1, 260 °C, and 5 MPa.

The cost-effective Cu-based catalysts for the efficient removal of acetylene from ethylene: The effects of Cu valence state, surface structure and surface alloying on the selectivity and activity

Cost-effective Cu-based catalysts with high activity and selectivity towards C2H4 formation are vital for the efficient removal of C2H2 from C2H4 in industry. A comprehensive understanding about the effects of Cu-based catalyst properties, including the valence state, surface structure and surface alloying, on the selectivity and activity towards C2H4 formation is essential for developing any novel Cu-based catalysts. In this work, C2H2 hydrogenation to C2H4 over various Cu-based catalysts, including Cu(0), Cu(I), Cu(II), and alloyed MCu(M = Ni, Pd, Pt, Au), were systematically investigated. The results indicated that the activity and selectivity of Cu catalysts with different oxidation states towards C2H4 formation are very different. Cu(I) led to the highest selectivity, while Cu(0) led to the highest activity. Moreover, the catalytic performances of Cu(I) and Cu(0) catalysts are closely related to their surface structures, especially their defective and stable (111) surfaces. For the most stable Cu(0) catalyst in reducing atmosphere, the activity and selectivity towards C2H4 formation on M-doped Cu(111) (M = Ni, Pd, Pt, Au) surface are affected by the surface d-band center, PdCu(111) surface with d-band center at the middle site has the best activity and selectivity towards C2H4 formation compared to the individual Cu(111) and Pd(111) surfaces. Thus, the activity of Cu-based catalysts and the selectivity of C2H2 hydrogenation towards C2H4 formation are determined by the valence state, surface structure, and surface d-band center of Cu catalysts. The catalytic activity and selectivity of all active surfaces can be predicted by analyzing the catalyst surface characteristics. The results are considerably beneficial to the development of new generation of Cu-based catalysts in the selective hydrogenation of C2H2.

Catalytic performance of Cu–Mg–Al in the one-step synthesis of 2-ethylhexanol from n-butyraldehyde

2-Ethylhexanol (2EHO), an important plasticizer alcohol, is industrially produced through three consecutive reaction processes. In this work, the one-step synthesis of 2EHO from n-butyraldehyde was exploited using Cu/Mg2.5AlOx catalyst. The effect of reaction conditions was investigated and the suitable reaction conditions were obtained as follows: a catalyst mass percentage of 10%, a H2 pressure of 4 MPa, a reaction time of 10 h and a reaction temperature of 180 °C. Under these reaction conditions, the yield of 2-ethylhexanol reached 62.8% and the selectivity ratio of 2-ethylhexanol to n-butanol (S2EHO/SBO) was 5.02. Based on designed experiments and the results of catalyst characterization using NH3-TPD, CO2-TPD and XPS techniques, it was clarified that the synergistic effect of acid–base and the interaction between Mg and Al were responsible for the better catalytic performance of Cu/Mg2.5AlOx. Then a plausible reaction mechanism of n-butyraldehyde self-condensation catalyzed by Cu/Mg2.5AlOx was presumed.

Performance comparison of mesoporous alumina supported Cu & Ni based catalysts in acetic acid reforming

Steam reforming of acetic acid (AcOH) was investigated over mesoporous alumina supported mono- and bi-metallic Ni and/or Cu based catalysts. Results obtained with mesoporous alumina supported catalysts were compared with another set of experiments performed using a commercial CuZn based HifuelR-120 catalyst and Ni impregnated HifuelR-120. Comparison of catalytic performances of Cu and Ni based catalysts showed that Cu activated the decomposition of AcOH giving mainly CH4 and CO2, while Ni was highly active for steam reforming reaction, yielding quite high H2 selectivities, reaching to 70%. This H2 selectivity was quite close to the equilibrium limit. Very low CO selectivity observed with HifuelR-120 and low CO/CO2 ratios observed especially with the Cu based catalysts clearly indicated that CO was not an intermediate of AcOH reforming reaction, but formed mainly as a result of reverse water gas shift reaction. Ni containing catalysts were shown to have high activity also for the reverse water gas shift reaction. Comparison of the performances of mono-metallic Ni and bi-metallic NiCu containing MA catalysts showed that the performance of the bi-metallic catalyst was better, yielding less CH4. Although the activities of nickel containing catalysts were quite high in steam reforming of AcOH, they yield more coke as compared to Cu based materials.

High-efficiency copper-based electrocatalysts for oxygen electroreduction by heating metal-phthalocyanine at superhigh temperature

The highly efficient Cu-based ORR catalysts (Cu–N–C) were obtained by the pyrolysis of mesoporous KIT-6 silica-supported phthalocyanines at superhigh temperature (1000 °C). The prepared Cu–N–C catalyst was demonstrated as one of the best Cu-based electrocatalysts for ORR, with 0.82 V half-wave potential in 0.1 M KOH and 0.72 V half-wave potential in 0.1 M HClO4. It showed the competitive ORR activity to high-performance Fe- or Co-based carbon catalysts. Moreover, the ORR catalytic performance of Cu–N–C could be further enhanced by co-doping few Fe species (Fe–Cu–N–C) into the carbon framework. It revealed about 30 mV higher half-wave potential and better stability than Cu–N–C catalyst in both alkaline and acidic media. Cu–N–C and Fe–Cu–N–C electrocatalysts could be produced at a scale of over 15 g by facilely enlarging the amount of phthalocyanine precursors. The high-efficiency ORR performance and scalable synthesis of Cu–N–C and Fe–Cu–N–C catalysts enabled them to be the potential substitutes to Pt-based electrocatalyst for ORR.

A new low-cost and effective method for enhancing the catalytic performance of Cu–SiO2 catalysts for the synthesis of ethylene glycol via the vapor-phase hydrogenation of dimethyl oxalate by coating the catalysts with dextrin

The influence of low-cost dextrin coating on the performance of Cu–SiO2 catalysts for the vapor-phase hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG) was systematically investigated. On the 0.05D-Cu–SiO2 catalyst, 99.8% DMO conversion and 92.3% EG selectivity could be obtained at 463K under 2.0gg-catal−1h−1 weight liquid hourly space velocity, which is almost four times higher than that of the catalyst without coating with dextrin. Characterization methods including N2 physisorption, XRD, TEM, H2 TPR, and XPS were carried out to elucidate the structure–performance relationship. Experimental results indicated that copper phyllosilicate contents decreased while well-dispersed CuO and Cu–O–Si units increased. The improved morphology with more compact nanosized crystalline copper structure resulted in more Cu+ species, which lead to better DMO conversion and EG selectivity in a long-term stability test.

Copper(II)-phenanthroline hybrid material as efficient catalyst for the multicomponent synthesis of 1,2,3-triazoles via sequential azide formation/1,3-dipolar cycloaddition

A copper(II)-phenanthroline hybrid material based on the SBA-15 architecture was prepared using a two-step synthesis through co-condensation of 5-[N,N-bis-3-(triethoxysilyl)propyl]ureyl-1,10-phenanthroline with tetraethoxysilane, followed by coordination of Cu(OAc)2. The obtained hybrid material, Cu(II)phen@SBA-15, was fully characterized, at each stage of the preparation, by means of bulk and molecular techniques to assess both textural and structural catalyst features using XRD, XPS, EPR, HRTEM, SEM, solid-state NMR UV–vis and IR analytical tools. The characterization results altogether confirmed the structural integrity of the mesoporous host and the successful anchoring of the copper-phenanthroline complex as discrete mononuclear Cu(II)L species. The catalytic performances of Cu(II)phen@SBA-15 were evaluated in the aqueous 1,3-dipolar cycloaddition of azides with alkynes using a multicomponent one-pot synthesis where organic azides were produced in situ from organic bromide (or aryl diazonium salts or epoxides), providing for safer synthetic technologies. The catalyst proved to be highly active under mild reaction conditions (0.5mol%, 70°C) over a broad range of substrates, providing 1,4-disubstituted-1,2,3-triazoles in high yields.

Bimetallic Nano Cu–Co Based Catalyst for Direct Ethanol Synthesis from Syngas and Its Structure Variation with Reaction Time in Slurry Reactor

The catalytic performance of Cu–Co/Al2O3 in the slurry reactor for direct ethanol synthesis from syngas was investigated. The reduced catalyst and catalyst reacted for 100, 300, 500, and 750 h were characterized by using XRD, TEM, EDS, BET, and ICP-MS techniques. Compared with that in the fixed-bed reactor, the catalyst in the slurry reactor exhibited higher selectivity to ethanol, which was above 70 wt % in the total alcohols. The structure variation of the bimetallic Cu–Co with reaction time is that CuCo2O4 was transformed into Cu–Co alloy after reduction, and Cu–Co alloy was decomposed into Cu and Co after reaction for 100 h. After reaction for 300 h, Co2C started to generate and Cu@Co@Co2C was formed as reacted for 500 h. All of Cu–Co alloy, Cu@Co, and Cu@Co@Co2C are highly selective to ethanol, which was maintained for 750 h. Meanwhile, the slurry solvent of PEG-400 is another reason for the high ethanol selectivity.

The catalytic performance of Cu n Au (n = 3–12) clusters for preferential oxidation of CO in hydrogen-rich stream

The CO preferential oxidation (CO-PROX) reaction is the simplest and most cost-effective method to purify reformed H2. We investigated the catalytic performance of Cu n Au (n = 3–12) clusters for CO-PROX in excess hydrogen using density functional theory calculations. The exploration on catalytic mechanism of CO-PROX reaction showed the formation of hydroxyl and atomic oxygen synchronously was the element step we found for the first time, and the mechanism also via the main intermediates of carboxylic. Our results showed that Cu n Au clusters reveal extremely activity for the CO-PROX reaction. In particular, Cu8Au regards as the best surface for CO-PROX reaction because of the lower activation barrier compared with other Cu n Au clusters. To explain the high catalytic activity of Cu n Au clusters, the nature of the interaction between adsorbate and substrate was also analyzed by detailed electronic projected density of states. Our studies provide insight into the Cu–Au catalysts, which may be helpful in developing efficient catalysts for important industrial reaction of CO-PROX.

Enhanced catalytic performance of Cu- and/or Mn-loaded Fe-Sep catalysts for the oxidation of CO and ethyl acetate

The Fe-modified sepiolite-supported Mn–Cu mixed oxide (CuxMny/Fe-Sep) catalysts were prepared using the co-precipitation method. These materials were characterized by means of the XRD, N2 adsorption–desorption, XPS, H2-TPR, and O2-TPD techniques, and their catalytic activities for CO and ethyl acetate oxidation were evaluated. The results show that catalytic activities of the CuxMny/Fe-Sep samples were higher than those of the Cu1/Fe-Sep and Mn2/Fe-Sep samples, and the Mn/Cu molar ratio had a distinct influence on catalytic activity of the sample. Among the CuxMny/Fe-Sep and Cu1Mn2/Sep samples, Cu1Mn2/Fe-Sep performed the best for CO and ethyl acetate oxidation, showing the highest reaction rate and the lowest T50 and T90 of 4.4 × 10− 6 mmol·g− 1·s− 1, 110, and 140 °C for CO oxidation, and 1.9 × 10− 6 mmol·g− 1·s− 1, 170, and 210 °C for ethyl acetate oxidation, respectively. Moreover, the Cu1Mn2/Fe-Sep sample possessed the best low-temperature reducibility and the lowest temperature of oxygen desorption as well as the highest surface Mn4 +/Mn3 + and Cu2 +/CuO atomic ratios. It is concluded that factors, such as the strong interaction between the Cu or Mn and the Fe-Sep support, good low-temperature reducibility, and good mobility of chemisorbed oxygen species, might account for the excellent catalytic activity of Cu1Mn2/Fe-Sep.

Novel synthesis and shape-dependent catalytic performance of Cu–Mn oxides for CO oxidation

Transition metal oxides with large specific surface area are attractive for high-activity catalysts, and hierarchical structures of transition metal oxides with porous feature possess the structural advantage in the transfer of gaseous reactant and product. In this work, porous Cu–Mn oxides with high surface area were successfully obtained through low-temperature coprecipitation method in alcohol/water solvent and then post-annealing. The addition of alcohol showed great influences on the shape and catalytic performances for CO oxidation. Dumbbell-like Cu–Mn oxide particles with splitting ends displayed high catalytic activity and a complete conversion of CO was achieved at 45°C, suggesting a shape-dependent catalytic activity. The oxidative activity was attributed to a combination of factors including specific surface area, active surface oxygen species and Mn(IV) cations. The results may supply a new thought to design high-performance Cu–Mn oxide catalysts.

Insight into the mechanism for the methanol synthesis via the hydrogenation of CO2 over a Co-modified Cu(100) surface: A DFT study

A comprehensive density functional theory calculation was employed to investigate the reaction mechanism of methanol synthesis on a Co-modified Cu(100) surface via CO2 hydrogenation. The Cu(100) surface with embedded small Co clusters prepared experimentally was employed as a model system to explore the effects of Co dopant on the catalytic performance of Cu(100) surface towards CH3OH synthesis. The activation energy barriers and the reaction energies of 16 elementary surface reactions were determined. Our calculated results show that the most favorable reaction pathway for the hydrogenation of CO2 to CH3OH follows the sequence of CO2 → HCOO* →H2COO* →H2COOH* →H2CO* →H3CO* →H3COH*, and the OH* group hydrogenation to H2 O* is the rate-limiting step with an activation barrier of 112.3 kJ/mol. It is noted that, since the strength of Co-O bond is stronger than that of Cu-O bond, the introducing of Co dopant on the Cu surface can facilitate the formation of key intermediates for the CH3OH synthesis. Especially, the stability of the unstable dioxomethylene intermediate (H2COO*) found on the pure Cu(100) surface can be obviously enhanced on the Co-doped Cu(100) surface. As a result, with respect to the undoped surface, the productivity and selectivity towards CH3OH production on the Cu(100) surface will be improved after dispersing small Co clusters on the surface.

Enhanced Photocatalytic Activity of Cu2O/Cu Heterogeneous Nanoparticles Synthesized in Aqueous Colloidal Solutions on Degradation of Methyl Orange

Heterogeneous Cu 2 O/Cu nanoparticles were synthesized by a colloidal chemistry approach using ascorbic acid as a reducing agent and polyvinylpyrrolidone as a surfactant. Morphology and structure of Cu 2 O/Cu nanoparticles were analyzed by SEM, XRD and N 2 sorption techniques. The catalytic performances of Cu 2 O/Cu nanoparticles for the degradation of methyl orange (MO) were investigated and reaction kinetics of MO degradation over the catalyst was also studied. The results show that the heterogeneous Cu 2 O/Cu nanoparticles display cobblestone-like morphology with particle sizes ranging from 20 nm to 40 nm, which are slightly smaller in particle size and higher in BET surface areas than pure Cu 2 O. The Cu 2 O/Cu nanoparticles demonstrate good potential on degradation of MO because Cu nanoparticles in the Cu 2 O/Cu heterostructures promote the interfacial charge-transfer kinetics between Cu and Cu 2 O. High initial MO concentration produces low degree of MO degradation, and increases the reaction time to reach equilibrium, and the degradation reactions follow the pseudo-first-order kinetics model. The Cu 2 O/Cu catalyst still exhibit good catalytic activity after 4 photodegradation cycles of MO solutions.