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.
Lithium difluoroborate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFBOP) and lithium difluorophosphate (LiPF2O2) are investigated as electrolyte additives to alleviate the severe cycle capacity fading of spinel LiMn2O4 cathode of lithium-ion batteries, especially at elevated temperatures. Compared with that of the routine electrolyte, the capacity retention is significantly improved at both room temperature and 55 °C by adding LiBOB and LiDFOB as electrolyte additives. Moreover, surface layer formation processes on the LiMn2O4 electrode in the presence of the LiBOB, LiDFOB, LiDFBOP and LiPF2O2 are investigated by photoelectron spectroscopy (XPS) and X-ray diffraction. According to the analysis results, BOB? anions from LiBOB or LiDFOB bond with the dissolved Mn2+ to form an insoluble and stable surface layer on the LiMn2O4 surface, which is beneficial to the suppression of the LiMn2O4 dissolution and electrolyte decomposition, and eventually to the improvement of the cycling performance at elevated temperatures.
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.
Three-dimensional TiO2 microspheres doped with N were synthesized by a simple single-step solvothermal method and the sample treated for 15 h (hereafter called TMF) was then used as scattering layers in the photoanodes of dye-sensitized solar cells (DSSCs). The TMF was characterized using scanning electron microscopy, high resolution transmission electron microscopy, Brunauer-Emmett-Teller measurements, X-ray diffraction, and X-ray photoelectron spectroscopy. The TMF had a high surface area of 93.2 m2?g–1 which was beneficial for more dye-loading. Five photoanode films with different internal structures were fabricated by printing different numbers of TMF scattering layers on fluorine-doped tin oxide glass. UV-vis diffuse reflection spectra, incident photon-to-current efficiencies, photocurrent-voltage curves and electrochemical impedance spectroscopy were used to investigate the optical and electrochemical properties of these photoanodes in DSSCs. The presence of nitrogen in the TMF changed the TMF microstructure, which led to a higher open circuit voltage and a longer electron lifetime. In addition, the presence of the nitrogen significantly improved the light utilization and photocurrent. The highest photoelectric conversion efficiency achieved was 8.08%, which is much higher than that derived from typical P25 nanoparticles (6.52%).
This study described a template-free method for the synthesis of hierarchically macro-mesoporous Mn-TiO2 catalysts. The promoting effect of Mn doping and the hierarchically macro-mesoporous architecture on TiO2 based catalysts was also investigated for the selective reduction of NO with NH3. The results show that the catalytic performance of TiO2 based catalysts was improved greatly after Mn doping. Meanwhile, the Mn-TiO2 catalyst with the hierarchically macro-mesoporous architecture has a better catalytic activity than that without such an architecture.
A method for the synthesis of particle brushes by grafting polylactic acid onto TiO2 nanoparticle is reported. The efficiency of grafting was enhanced by combining azeotropic separation of water with polycondensation in a single pot. PLA/TiO2 brushes synthesized with different ratio of lactic acid and TiO2 were characterized by various techniques such as FT-IR, XRD, TEM, XPS, 1H and 13C NMR. TEM analysis indicates that the sizes of TiO2 nanoparticles are between 2 and 8 nm. DLS was used to determine overall size of particle brush and average size varied between 59.68–65.83 nm. Zeta potential measurement indicated high stability of water dispersed particles brushes with measured values of ?30.1 to ?37.1 mV for brushes prepared with PLA/TiO2 ratio of 50:1 and 20:1 respectively. The DSC and TGA analysis showed that PLA/TiO2 nanocomposites have good thermal stability.
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.
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
Heavy hydrocarbons (HHCs) in soils impacted by crude oil spills are generally recalcitrant to biodegradation due to their low bioavailability and complex chemical structure. In this study, soils were pretreated with varying concentrations of ultraviolet radiation A (UVA) or ultraviolet radiation C (UVC) activated titanium dioxide (TiO2) (1%–5%) under varying moisture conditions (0%–300% water holding capacity (WHC)) to enhance biodegradation of HCCs and shorten remediation timeframes. We demonstrate that pretreatment of impacted soils with UVC-activated TiO2 in soil slurries could enhance bioremediation of HHCs. Total petroleum hydrocarbon (TPH) removal after 24 h exposure to UVC (254 nm and 4.8 mW/cm2) was (19.1 ± 1.6)% in slurries with 300% WHC and 5 wt-% TiO2. TPH removal was non-selective in the C15-C36 range and increased with moisture content and TiO2 concentration. In a 10-d bioremediation test, TPH removal in treated soil increased to (26.0 ± 0.9)%, compared to (15.4 ± 0.8)% for controls without photocatalytic pre-treatment. Enhanced biodegradation was also confirmed by respirometry. This suggests that addition of UVC-activated TiO2 to soil slurries can transform recalcitrant hydrocarbons into more bioavailable and biodegradable byproducts and increase the rate of subsequent biodegradation. However, similar results were not observed for soils pretreated with UVA activated TiO2. This suggests that activation of TiO2 by sunlight and direct addition of TiO2 to unsaturated soils within landfarming setting may not be a feasible approach. Nevertheless, less than 1% of UVA (7.5 mW/cm2) or UVC (1.4 mW/cm2) penetrated beyond 0.3 cm soil depth, indicating that limited light penetration through soil would hinder the ability of TiO2 to enhance soil bioremediation under land farming conditions.
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.
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
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.
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.
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.
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.
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.
The effect of thermal pretreatment on the active sites and catalytic performances of PtSn/SiO2 catalyst in acetic acid (AcOH) hydrogenation was investigated in this article. The catalysts were characterized by N2 physical adsorption, X-ray diffraction, transmission electron microscopy, pyridine Fourier-transform infrared spectra, and H2-O2 titration on its physicochemical properties. The results showed that Pt species were formed primarily in crystalline structure and no PtSnx alloy was observed. Meanwhile, with the increment of thermal pretreatment temperature, Pt dispersion showed a decreasing trend due to the aggregation of Pt particles. Simultaneously, the amount of Lewis acid sites was remarkably influenced by such thermal pretreatment owning to the consequent physicochemical property variation of Sn species. Interestingly, the catalytic activity showed the similar variation trend with that of Lewis acid sites, confirming the important roles of Lewis acid sites in AcOH hydrogenation. Moreover, a balancing effect between exposed Pt and Lewis acid sites was obtained, resulting in the superior catalytic performance in AcOH hydrogenation.
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
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 CO2 capturing and sequestration are of importance in environmental science. A new type of microporous coordination polymer (Ni/PAPy) with secondary amine groups has been successfully prepared. Taking advantage of the synergistic effect of metal-electrostatic and hydrogen bonding interactions between the Ni/PAPy network and CO2 molecules, the CO2 uptake capacity of the microporous coordination polymer reaches up to 4.82 mmol g?1 (1.0 bar, 273 K) with the high selectivities (CO2/N2?=?83, CO2/CH4?=?16), making the Ni/PAPy a promising microporous material for application of CO2 uptake and separation. For comparison, the microporous coordination polymer without secondary amine groups (Ni/PPy) is also prepared.
Graphical Abstract Taking advantage of the synergistic effect of metal-electrostatic and hydrogen bonding interactions between the Ni/PAPy network and CO2 molecules, the Ni/PAPy can be considered as a promising microporous material for application of CO2 uptake and separation.
