Plasmonic enhancement is an effective method to improve the power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs). The size and amount of plasmon play key roles in plasmonic effect; however, the report on the relationship between morphology and processing of plasmon is rare. In this work, a series of Au nanoparticles (NPs) inlaid into TiO2 nanotube (NT) based photoanodes have been synthesized through tuning HAuCl4 solution concentration and irradiation time during the photoreduction process. Meanwhile, the optical and photoelectrical properties of these plasmonic DSSCs have also been verified. The results demonstrate that the optimized plasmonic DSSC (irradiation time: 5 min, solution concentration: 0.5 mM) showed a 19.0% improvement of PCE, compared to the reference DSSC without Au NPs. The improved PCE is mainly attributed to the enhanced photocurrent generated by surface plasmon resonance (SPR) effect of small sized Au NPs as well as light scattering effect of large sized particles.
In the present study, we present a facile strategy to synthesis Co3O4 materials with different morphology. Experimental results show that Co3O4 materials with flower-like, fiber, sheet-like and rod morphologies have been successfully prepared by hydrothermal synthesis in different solvent. The effect of the morphology on the electrochemical catalytic properties were also studied. It is found that sheet-like Co3O4 exhibits the best activity towards oxygen evolution reaction (η10?=?390 mV) in 1 M KOH, which can be attribute to its short electrolyte infiltration diffusion path lengths and low charge transfer resistant.
Graphical Abstract
LSV curves measured at 5 mV/s in 1 M KOH solution for OER, the inset image is FE-SEM image of prepared Co3O4 materials. a Flower, b fiber, c sheet and d rod.
A wide range of experimental data are reported for the first time on the TiO2 prepared by hydrolysis of highly concentrated Ti(OiPr)4 in water solutions of quaternary ammonium compounds (QACs). These TiO2 materials have been shown to be photocatalytically active under visible light irradiation (LED, 450 nm) using acetone as a model substrate oxidized in the gas phase. Five-fold increase in activity in comparison with the commercial photocatalyst KRONOClean 7000 is achieved. Colloidal solutions of hydrolyzed Ti(OiPr)4 have been studied by SAXS method suggesting the way in which QACs solutions may influence the final composition of TiO2. Phase composition, morphology, texture and surface properties of the modified TiO2 have been studied using XRD, BET, SEM and low-temperature FTIR with CO probe. The surface elemental composition has been investigated by XPS method. Additional low-energy levels and high concentration of acid surface sites originated from N/C-doping, are likely to be the main reasons for exceptional photocatalytic performance of these samples.
The influence of ZrO2 phase on the product selectivity arising from the preparation method of Cu/ZrO2 is studied in the gas phase conversion of cyclohexanol. This study results are supported by NH3-TPD, XRD, pyridine-FTIR and N2O pulse chemisorptions measurements. However, N2O pulse chemisorptions studies did not reveal significant differences between the two catalysts. The product selectivity is completely dependent on the ZrO2 phase which ultimately led to the differences in the acidic properties observed through NH3-TPD and pyridine-FTIR experiments. Catalyst poisoning experiments using NH3 co-feeding brought a reversal in the product selectivity.
Graphical Abstract
Cu/ZrO2 catalyst prepared by impregnation method containing monoclinic ZrO2 yields cyclohexanone and Cu/ZrO2 catalyst prepared by coprecipitation method with tetragonal ZrO2 phase possessing strong acidic sites yields benzene when cyclohexanol is contacted in vapour phase conditions
The effects of sub-nanometer atomic layer deposition films of titania and alumina are compared for the acrolein hydrogenation selectivity of Pt/SrTiO3 catalysts. The titania-overcoated catalyst is similar to strong metal-support interaction catalysts formed by high temperature reduction, with a thin titania film on top of the supported Pt nanoparticles and an increase in allyl alcohol selectivity, neither of which are observed for the alumina-overcoated catalyst.
The present study was focused on the degradation of Atrazine (ATZ) and major by-products (DEA, DIA, DEDIA and ATZ-OH) from water by photoelectrocatalytic (PEC) oxidation process under solar light. The undoped TiO2, sub-stoichiometric TiO2 (TiO2?x) and codoped TiO2 (TiO2:WN) photoanodes were prepared by means of a radio frequency magnetron sputtering (RF-MS) deposition process. The X-ray photoelectron spectra (XPS) analysis shows that the N and W atoms were incorporated into the O and Ti lattice sites of TiO2 respectively (case of TiO2:WN film), while the XPS measurements of the TiO2?x films composition was determined to be TiO1.9. The UV–Vis transmittance spectra shows that in the case of the TiO2:WN films, the presence of nitrogen and tungsten improve the optical response of TiO2 under visible range compare to the presence of oxygen vacancies in to the TiO2?x films. The experimental results under solar light with an initial concentration of ATZ (100 µg L?1) show that after 180 min of treatment, the degradation of ATZ were 34.98%, 68.57% and 94.33% using TiO2, TiO2?x and TiO2:WN photoanodes, respectively. These results of ATZ degradation proved that TiO2:WN photoanode was more photoactive under solar light. The evolution by-products of ATZ under sunlight show that the principal mechanism of ATZ degradation was the oxidation of alkyl side chain and dealkylation.
CO selective methanation is a promising route for the purification of CO in H2-rich gas for on-board H2-based fuel cells. Herein, we synthesized a Zr-modified SBA-15 supported Ni catalyst, which exhibits both high catalytic performance, deep-removing CO concentration to below 10 ppm with a selectivity higher than 50% in a very low-temperature range (170–220 °C), and long-term stability. The results of XRD, XPS, TPR, TPD and TEM characterizations reveal that the doping of Zr not only improves the dispersion of Ni species, enhances the CO adsorption, but also suppresses the CO2 adsorption, resulting in the prominent catalytic performance.
The hollow TiO2@g-C3N4 composites were synthesized by a facile stirring method. The phase compositions, optical properties, and morphologies of the samples were characterized via X-ray diffraction, scanning electron microscope, transmission electron microscopy, high resolution transmission electron microscopy, fourier transform infrared spectroscopy, N2 adsorption–desorption, UV–Vis diffuse reflectance spectroscopy and Photoluminescence. The photocatalyitc performance was evaluated by reduction carbon dioxide under visible light irradiation. The results indicated that TiO2@g-C3N4 nanocomposites displayed higher photocatalytic activity compared with pure g-C3N4. The increased photocatalytic activity of TiO2@g-C3N4 nanocomposites can be attributed to facilitating the photo-induced electron–hole separation efficiency and enhancing the photo-induced electron migration.
Heterogeneous catalysts with convenient recyclability and reusability are vitally important to reduce the cost of catalysts as well as to avoid complex separation and recovery operations. In this regard, magnetic MIL-100 (Fe)@SiO2@Fe3O4 microspheres with a novel core-shell structure were fabricated by the in-situ self-assembly of a metal-organic MIL-100(Fe) framework around pre-synthesized magnetic SiO2@Fe3O4 particles under relatively mild and environmentally benign conditions. The catalytic activity of the MIL-100(Fe)@SiO2@Fe3O4 catalyst was tested for the liquid-phase acetalization of benzaldehyde and glycol. The MIL-100(Fe)@SiO2@Fe3O4 catalyst has a significant amount of accessible Lewis acid sites and therefore exhibited good acetalization catalytic activity. Moreover, due to its superparamagnetism properties, the heterogeneous MIL-100(Fe)@SiO2@Fe3O4 catalyst can be easily isolated from the reaction system within a few seconds by simply using an external magnet. The catalyst could then be reused at least eight times without significant loss in catalytic efficiency.
Photocatalytic hydrogen evolution is considered as one of the promising pathways to settle the energy crises and environmental issues by utilizing solar energy. In this paper, noble-metal-free Ni2P was used as cocatalyst to enhance g-C3N4 for photocatalytic hydrogen production under visible light irradiation (λ?>?420 nm). Characterization results indicated that Ni2P nanoparticles were successfully loaded onto g-C3N4, which can significantly contribute to accelerate the separation and transfer of photogenerated electron. The hydrogen evolution rate reached ～?270 µmol h?1 g?1 and the apparent quantum yield (AQY) was ～?2.85% at 420 nm. Meanwhile, there is no obviously decrease of the hydrogen production rate even after 36 h under visible light illumination. In addition, the mechanism of photocatalytic hydrogen evolution was also elaborated in detail.
Vanadia species formed on the surface depend on the K/V atomic ratio. At small K/V ratios, Raman spectra show the formation of the K-doped and K-perturbed monomeric species. At K/V?=?1, kristalline KVO3 is mainly present on the surface. In situ high temperature XRD-results exhibit a promoting effect on the anatase to rutile phase transformation in the presence of 0.03 and 0.21 wt% potassium. Large amount of K (3 wt%) provides thermal stability of V/Ti/O catalyst and no transformation is found up to 600?°C. Reduction of vanadia K-doped vanadia catalysts is moved to higher temperatures than for the catalyst without potassium. The catalyst having 0.21 wt% K possesses the highest activity in o-xylene oxidation. Furthermore, the K-doped monomeric vanadia species in this catalyst leads to a promoted adsorption or a prevented desorption of phthalide, resulting in a decreased selectivity towards phthalide and COx and a increased PA selecticity.
Ternary heterojunctions g-C3N4/ZnS/CuS with different morphologies were constructed. The g-C3N4/ZnS/CuS (hexagonal-nanosheets) exhibited the largest photocurrent, the best photocatalytic and electrochemical activity, which revealed the influence discipline of different morphologies on photoconductivity, photo/electro-catalytic activity. It indicated that this heterojunction can be used as an excellent photoconductor device, a high-efficiency photo/electro-catalyst.
A series of Mn-promoted 15 wt-% Ni/Al2O3 catalysts were prepared by an incipient wetness impregnation method. The effect of the Mn content on the activity of the Ni/Al2O3 catalysts for CO2 methanation and the comethanation of CO and CO2 in a fixed-bed reactor was investigated. The catalysts were characterized by N2 physisorption, hydrogen temperature-programmed reduction and desorption, carbon dioxide temperature-programmed desorption, X-ray diffraction and highresolution transmission electron microscopy. The presence of Mn increased the number of CO2 adsorption sites and inhibited Ni particle agglomeration due to improved Ni dispersion and weakened interactions between the nickel species and the support. The Mn-promoted 15 wt-% Ni/Al2O3 catalysts had improved CO2 methanation activity especially at low temperatures (250 to 400 °C). The Mn content was varied from 0.86% to 2.54% and the best CO2 conversion was achieved with the 1.71Mn-Ni/Al2O3 catalyst. The co-methanation tests on the 1.71Mn-Ni/Al2O3 catalyst indicated that adding Mn markedly enhanced the CO2 methanation activity especially at low temperatures but it had little influence on the CO methanation performance. CO2 methanation was more sensitive to the reaction temperature and the space velocity than the CO methanation in the co-methanation process.
Firstly, h-CdS/c-CdS homojunction was prepared by solvothermal method with controlling the Cd-to-S molar ratio. Then, the MoS2/h-CdS/c-CdS nanocomposites were constructed by ultrasonic method with different MoS2 amount. The experimental results showed that when the molar ratio of Cd and S was 1:1 and the amount of MoS2 was 1.5 wt%, the MoS2/h-CdS/c-CdS nanocomposites exhibited excellent photocatalytic performance for hydrogen evolution under visible light. The total amount of hydrogen evolution was 3753.12 µmol for 5 h, and its average hydrogen evolution rate was 40.79 mmol h?1 g?1 with an apparent quantum efficiency of 38.16% irradiated at 420 nm, which was about 7.3 times when compared with the h-CdS/c-CdS homojunction (Cd:S?=?1:8). The enhanced photocatalytic performance of MoS2/h-CdS/c-CdS could be attributed to the improved specific surface area and formation of well bonded interface structure, which not only enhanced the response to visible light but also decreased the recombination rates of photogenerated charge carriers.
Electrodeposition of Zn, Co and ZnCo from acid sulfate solutions onto steel was investigated in this first part of a study
of the effects of SiC or Al2O3 particles on these processes and the formation of ZnCo–SiC and ZnCo–Al2O3 electrocomposites. Zn electrodeposition shows a well-defined pre-bulk region, where the hydrogen evolution reaction (HER)
and Zn underpotential deposition (upd) compete. Zn bulk electrodeposition begins with primary nucleation and diffusion-controlled
growth, strongly dependent on conditions favoring previous Zn upd against HER. It is assumed that this first bulk process
takes place over the upd Zn. Zn bulk electrodeposition is followed by secondary nucleation and growth. Co electrodeposition
begins with a slow reduction in parallel with HER, followed by a faster reduction. strongly hinders the initial reduction. The ZnCo and Zn electrodeposition curves are initially similar, retaining features of pre-bulk and bulk Zn electrodeposition. 相似文献
This paper overviews the development of the anthraquinone auto-oxidation (AO) process for the production of hydrogen peroxide in China and abroad. The characteristics and differences between the fixed-bed and fluidized-bed reactors for the AO process are presented. The detailed comparison indicates that the production of hydrogen peroxide with the fluidized-bed reactor has many advantages, such as lower operation cost and catalyst consumption, less anthraquinone degradation, higher catalyst utilization efficiency, and higher hydrogenation efficiency. The key characters of the production technology of hydrogen peroxide based on the fluidized-bed reactor developed by the Research Institute of Petroleum Processing, Sinopec are also disclosed. It is apparent that substituting the fluidized-bed reactor for the fixed-bed reactor is a major direction of breakthrough for the production technology of hydrogen peroxide in China.
A series of Al2O3 and CeO2 modified MgO sorbents was prepared and studied for CO2 sorption at moderate temperatures. The CO2 sorption capacity of MgO was enhanced with the addition of either Al2O3 or CeO2. Over Al2O3-MgO sorbents, the best capacity of 24.6 mg- CO2/g-sorbent was attained at 100 °C, which was 61% higher than that of MgO (15.3 mg-CO2/g-sorbent). The highest capacity of 35.3 mg-CO2/g-sorbent was obtained over the CeO2-MgO sorbents at the optimal temperature of 200 °C. Combining with the characterization results, we conclude that the promotion effect on CO2 sorption with the addition of Al2O3 and CeO2 can be attributed to the increased surface area with reduced MgO crystallite size. Moreover, the addition of CeO2 increased the basicity of MgO phase, resulting in more increase in the CO2 capacity than Al2O3 promoter. Both the Al2O3-MgO and CeO2-MgO sorbents exhibited better cyclic stability than MgO over the course of fifteen CO2 sorption-desorption cycles. Compared to Al2O3, CeO2 is more effective for promoting the CO2 capacity of MgO. To enhance the CO2 capacity of MgO sorbent, increasing the basicity is more effective than the increase in the surface area.
A sol-gel technique has been developed for the synthesis of a magnetite-silica-titania (Fe3O4-SiO2-TiO2) tertiary nanocomposite with improved photocatalytic properties based on the use of inexpensive titania and silica precursors. The exceptional photocatalytic activity of the resulting materials was demonstrated by using them to photocatalyze the degradation of methylene blue solution. The best formulation achieved 98% methylene blue degradation. An interesting feature of the present work was the ability to magnetically separate and reuse the catalyst. The efficiency of the catalyst remained high during two reuses. The synthesized nanomaterials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, ultra-violet-visible spectroscopy, diffuse reflectance spectroscopy, and thermogravimetric analysis. XRD analysis revealed the formation of multicrystalline systems of cubic magnetite and anatase titania crystals. SEM and TEM characterization revealed well-developed and homo-geneously dispersed particles of size less than 15 nm. FTIR spectra confirmed the chemical interaction of titania and silica. It was further noticed that the optical properties of the prepared materials were dependent on the relative contents of their constituent metal oxides.
In this research, an efficient recyclable nano-inorganic composite of CuO/ZnO/Al2O3 (CuO/ZnO/Al2O3 nanocatalyst) is prepared, characterized and used for the amination of aryl halides with aqueous ammonia in water. The catalyst was prepared by co-precipitation method and characterized by various techniques such as the X-ray diffraction, scanning electron microscope, energy dispersive spectroscopy, and brunauer–Emmett–Teller surface area analysis. Various aryl halides reacted with aqueous ammonia and corresponding products were obtained in high yields. CuO/ZnO/Al2O3 nanocatalyst as an efficient stable catalyst is recyclable up to five consecutive runs by simple filtration.
Graphical Abstract
An efficient recyclable nano-inorganic composite of CuO/ZnO/Al2O3 (CuO/ZnO-Al2O3 nanocatalyst) is prepared, characterized and used for the amination of aryl halides with aqueous ammonia in water.
The origin of the effect of non-faradaic electrochemical modification of catalytic activity (NEMCA) or Electrochemical Promotion
was investigated via temperature-programmed-desorption (TPD) of oxygen, from polycrystalline Pd films deposited on 8 mol%Y2O3–stabilized–ZrO2 (YSZ), an O2− conductor, under high-vacuum conditions and temperatures between 50 and 250 °C. Oxygen was adsorbed both via the gas phase
and electrochemically, as O2−, via electrical current application between the Pd catalyst film and a Au counter electrode. Gaseous oxygen adsorption gives
two adsorbed atomic oxygen species desorbing at about 300 °C (state β1) and 340–500 °C (state β2). The creation of the low temperature peak is favored at high exposure times (exposure >1 kL) and low adsorption temperatures
(Tads < 200 °C). The decrease of the open circuit potential (or catalyst work function) during the adsorption at high exposure times,
indicates the formation of subsurface oxygen species which desorbs at higher temperatures (above 450 °C). The desorption peak
of this subsurface oxygen is not clear due to the wide peaks of the TPD spectra. The TPD spectra after electrochemical O2− pumping to the Pd catalyst film show two peaks (at 350 and 430 °C) corresponding to spillover Oads and
according to the reaction:
The formation of the spillover oxygen species is an intermediate stage before the formation of the atomic adsorbed oxygen, Oads. Mixed gaseous and electrochemical adsorption was carried out in order to simulate the Electrochemical Promotion conditions.
The initial surface coverage with oxygen from the gas phase plays a very important role on the high or low effect of polarization.
In general mixed adsorption leads to much higher oxygen coverages compare with that observed either under gaseous or electrochemical
adsorption. The binding strength of the atomic adsorbed oxygen (state β2) was investigated as a function of applied potential. It was found that the binding energy decreases linearly with increasing
catalyst potential and work function. Similar behavior has been observed for oxygen adsorption on Pt, Ag and Au deposited
on YSZ in previous studies. 相似文献
