Cobalt sulfide quantum dots (CoSx QDs) modified TiO2 nanoparticles are prepared with a precipitation-deposition method using TiO2, cobalt acetate and sodium sulfide as the precursors. CoSx QD acts as ...an effective cocatalyst, which accelerates the transfer of the photo-generated electrons and serves as the active site for the reaction between electrons and H2O, thus enhancing the separation of the e−/h+ pairs and the photocatalytic H2 production activity of TiO2. The amount of CoSx exhibits an optimum value at about 5% (mole ratio to TiO2), at which the H2 production rate achieves 838 μmol h−1 g−1 using ethanol as the sacrificial reagent. This exceeds that of the pure TiO2 by more than 35 times.
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•CoSx/TiO2 heterojunction photocatalysts are synthesized.•The CoSx/TiO2 shows remarkable UV and visible light photocatalytic activity.•The hydrogen evolution rate was greatly improved.•The intimate contact of the phases promotes the charge transfer and separation.
A single-metal redox flow battery employing chromium(III) acetylacetonate in tetraethylammonium tetrafluoroborate and acetonitrile has been investigated using electrochemical techniques. Cyclic ...voltammetry was used to evaluate electrode kinetics. Four redox couples were observed in the stable potential window. The Cr
II/Cr
III, Cr
I/Cr
II, Cr
III/Cr
IV and Cr
IV/Cr
V redox couples all appeared to be quasi-reversible, with the Cr
III/Cr
IV couple exhibiting comparatively slow kinetics. A cell potential of 3.4
V was measured for the one-electron disproportionation of the neutral Cr
III complex. The diffusion coefficient for chromium acetylacetonate in the supporting electrolyte solution was estimated to be in the range of 5.0–6.2
×
10
−7
cm
2
s
−1 at room temperature. The charge–discharge characteristics of this system were evaluated in an H-type glass cell, and coulombic and energy efficiencies of approximately 55% and 20%, respectively, were obtained.
A dense membrane consisting of two-phases: molten carbonate for the conduction of carbonate ions and Bi1.5Y0.3Sm0.2O3 (BYS) for the conduction of oxygen ions, was synthesized and used for selective ...permeation of CO2 at high temperatures. Since CO2 is transported by CO32−, these membranes provide infinite selectivity for CO2 over other species such as Ar, He or N2.The dual-phase membranes were synthesized by the direct infiltration molten carbonate into porous BYS supports with internal surface modified with γ-Al2O3 to improve the wettability. Permeation took a long time to reach a steady state at the initial stage of high temperature CO2 separation due to the reversible phase transform of the oxygen ions conduction phase between the rhombohedral structure and cubic fluorite structure. The CO2 permeation flux for the dual phase membrane increases with increasing temperature (500–650°C) with apparent activation energy for CO2 permeation of 113.4kJ/mol. The CO2 permeation flux increases with increasing sweep gas flow rate and reaches a value of 0.083mL/cm2/min at 650°C and helium flow rate of 125mL (STP)/min. The BYS–carbonate membrane offers higher CO2 permeance than carbonate dual-phase membranes with lithium–cobaltite or yttrium stabilized zirconia as the oxygen ionic conducting phase.
► Thin doped bismuth oxide–carbonate membrane was synthesized. ► Controlling carbonate wettability of ceramic phase was critical to carbonate infiltration. ► Phase transformation of bismuth oxide affects CO2 permeation. ► New dual-phase membranes exhibit high CO2 permeance.
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► Two ionic liquids are used in the V(acac)
3 redox flow battery. ► Cyclic voltammograms and kinetics of reactions are tested. ► Charge–discharge performance shows a reasonable ...coulombic efficiency.
Tetrabutylammonium hexafluorophosphate (TEAPF
6) and 1-ethyl-3-methyl imidazolium hexafluorophosphate (EMIPF
6) are synthesized and used as the supporting electrolytes of a non-aqueous redox flow battery using vanadium acetylacetonate (V(acac)
3) as the active species. The conductivity and cyclic voltammograms of the electrolytes of the two ionic liquids are measured. The cyclic voltammograms show that both of them are stable in an operating potential range (−2.5–1.5
V). The diffusion coefficients of V(acac)
3 in the electrolytes are determined as 0.92–1.47
×
10
−6
cm
2
s
−1 in 0.5
mol
l
−1 TEAPF
6 and 2.35–3.79
×
10
−6
cm
2
s
−1 in 0.5
mol EMIPF
6, respectively. The charge–discharge performances of the two non-aqueous V(acac)
3 containing electrolytes with TEAPF
6 and EMIPF
6 as the supporting electrolytes are evaluated in an H-type glass cell. The coulombic efficiencies are measured as in the range of 53.31–57.44% at 50% state of charge with an electrolyte containing 0.2
mol
l
−1 TEAPF
6, and as in the range of 46.04–43.46% for the electrolyte containing EMIPF
6 with the same concentrations of the components.
In this article, we investigated the interactions between oxidized single-wall carbon nanotubes and three amino acids. A simple and environmental benign method to realize solubility of oxidized ...single-wall carbon nanotubes (OSWNT) in water was described. The amino acids used in this study include l-glycine (Gly), l-lysine (Lys), and l-phenylalanine (Phe). The OSWNT became soluble in water under ambient conditions and formed a stable suspension when amino acids (AA) were adsorbed on it. The interactions between OSWNT and three AA were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA). The results indicate that there is an increasing in the diameter of OSWNT after AA adsorption. The OSWNT with different diameters were separated as a result of AA adsorption. The smaller the diameter of OSWNT, the more the AA adsorption amount is. The adsorbed amount of different AA on OSWNT follows the trend: Lys > Phe > Gly. The Π–Π stacking is an important factor to realizing adsorption of Phe zwitterions on the sidewall of OSWNT; but for Gly and Lys zwitterions, polar interaction is a determinant factor to realizing adsorption on the sidewall of OSWNT. The AA zwitterions were adsorbed on the surface of OSWNT by conjunct interaction of the Π–Π stacking, polar interaction, hydrogen bond, and covalent bonding. Hydrogen bond and covalent bond, formed with oxygen containing groups, is dominant at the end of OSWNT. The catalysis property of OSWNT makes a noticeable reduction of decomposition temperature for AA adsorbed on OSWNT.
A 5 wt% BaMnO3-CeO2 composite catalyst prepared by the one-pot method exhibits extraordinary catalytic performance for nitrogen monoxide (NO) direct decomposition into N2 and O2; however, the reasons ...for the high activity remain to be explored. Here, the catalyst was prepared by mechanical mixing and then subjected to thermal treatment at different temperatures (600–800 °C) to explore the underlying reasons. The thermal pre-treatment at temperatures higher than 600 °C can improve the catalytic activity of the mechanically mixed samples. The 700 °C-treated 5%BaMnO3-CeO2 sample shows the highest activity, with NO conversion to N2 of 13.4%, 40.6% and 57.1% at 600, 700, and 800 °C, respectively. Comparative activity study with different supports (ZrO2, TiO2, SiO2, Al2O3) reveals that CeO2 is indispensable for the high performance of a BaMnO3-CeO2 composite catalyst. The Ce species (mainly Ce3+) in CeO2 components diffuse into the lattice of BaMnO3, generating oxide ion vacancy in both components as evidenced by X-ray photoelectron spectroscopy and Raman spectra, which accelerates the rate-determining step and thus higher activity. The chemisorption results show that the interaction between BaMnO3 and CeO2 leads to higher redox activity and mobility of lattice oxygen. This work demonstrates that engineering the oxide ion vacancy, e.g., by thermal treatment, is an effective strategy to enhance the catalytic activity towards NO direct decomposition, which is expected to be applicable to other heterogeneous catalysts involving oxide ion vacancy.
The electrochemical oxidation of carbon at the anode of a direct carbon fuel cell (DCFC) includes charge transfer steps and chemical steps. A microstructural model of carbon particle is built, in ...which perfect graphene stacks are taken as the basic building blocks of carbon. A modified mechanism taking account of the irreversibility of the process and supposing that the electrochemical oxidation of carbon takes place only at the edges of the graphene sheets is proposed. A Tafel type overall rate equation is deduced along with expressions of exchange current density (
j
0) and activation polarization (
η
act). The performance of carbon black and graphite as the fuel of DCFC is examined. It has been found that
j
0 is in the range of 0.10–6.12
mA
cm
−2 at 923–1123
K and
η
act is in the range of 0.024–0.28
V at 923–1123
K with current density in 10–120
mA
cm
−2. Analysis of the
j
0,
η
act values and the product composition reveals that the charge transfer steps as well as the oxygen ion absorption steps are both important for the reaction rate. The activity of the carbon material with respect to atom location is introduced to the open circuit potential difference (OCP) calculation with Nernst equation.
The performance of a composite electrolyte composed of a samarium doped ceria (SDC) and a binary eutectic carbonate melt phase has been examined. This material shows higher ionic conductivity than ...pure SDC in intermediate temperature region. SDC with different morphologies is obtained by co-precipitation, sol–gel and glycine-nitrate combustion preparation techniques. A tri-layer single cell is prepared with a cost-effective co-pressing and co-sintering technique. It is found that the surface properties of SDC and the electrolyte thickness have a great influence on the fuel cell performance. When the co-precipitated SDC is used as the electrolyte component and CO
2/O
2 gas mixture is adopted as the cathode oxidant gas, a fuel cell with an excellent performance is obtained, which has a peak power output of 1704
mW
cm
−2 at a current density of 3000
mA
cm
−2 at 650
°C. The influence of cathode atmosphere is examined with conductivity measurement and fuel cell performance test. The results support the concept of O
2−/H
+/CO
3
2− ternary conduction.
•Tungsten phosphide was used in the selective production of phenols from lignin.•Hot compressed water–ethanol was used as the solvent.•6.70wt% monophenols was obtained.•Activated carbon supported ...tungsten phosphide shows the best.•Doping with Fe and Ni improve phenol selectivity.
Production of phenols from alkaline lignin over a tungsten phosphide catalyst in a hot compressed water–ethanol mixed solvent is examined. The small molecular products mainly consist of five phenols, i.e. 2-methoxy-phenol (guaiacol), 2-methoxy-4-methyl-phenol, 2-methoxy-4-ethyl-phenol, 2-methoxy-4-acetyl-phenol and 2-methoxy-4-propyl-phenol. The activated carbon supported catalyst gives the highest overall phenols yield, 67.0mg/g lignin, while the catalysts with other supports exhibit much lower overall yield. Ni and Fe doping of the tungsten phosphide improve phenols selectivity but lower the overall phenols yield. In addition, the result of MALDI-TOF analysis indicates that a longer reaction time leads to the formation of polymers with molecular weights of m/z 701–1040 due to the re-polymerization reactions. Therefore, the yield of the monophenols decreases with the increase of the reaction time.
► Mn
III/IV, Mn
II/III and Mn
I/II couples observed in voltammetry for Mn(acac)
3. ► Cell potential of 1.1
V observed for the one-electron disproportionation of Mn(acac)
3. ► Diffusion coefficient of ...Mn(acac)
3 in the electrolyte is 3–5
×
10
−6
cm
2
s
−1. ► Coulombic efficiencies increased with cycling. ► Energy efficiencies stable at ∼21% for unoptimized cell.
A single-metal redox flow battery employing manganese(III) acetylacetonate in tetraethylammonium tetrafluoroborate and acetonitrile has been investigated. Cyclic voltammetry was used to evaluate electrode kinetics and reaction thermodynamics. The Mn
II/Mn
III and Mn
III/Mn
IV redox couples appeared to be quasi-reversible. A cell potential of 1.1
V was measured for the one-electron disproportionation of the neutral Mn
III complex. The diffusion coefficient for manganese acetylacetonate in the supporting electrolyte solution was estimated to be in the range of 3–5
×
10
−6
cm
2
s
−1 at room temperature. The charge–discharge characteristics of this system were evaluated in an H-type glass cell. Coulombic efficiencies increased with cycling suggesting an irreversible side reaction. Energy efficiencies for this unoptimized system were ∼21%, likely due to the high cell-component overpotentials.
