共查询到20条相似文献,搜索用时 453 毫秒
1.
V. V. Kuznetsov B. I. Podlovchenko K. V. Kavyrshina Yu. M. Maksimov 《Russian Journal of Electrochemistry》2010,46(12):1353-1359
The electrocatalytic Pt-Mo system was obtained by formation of platinum particles on the Mo surface under its contact with
PtC62− (PtCl42−) under the open circuit conditions. Cyclic voltammograms of the obtained Pt(Mo) electrodes feature well pronounced peaks
of hydrogen adsorption and desorption on Pt particles. Nonuniform platinum distribution across the electrode surface was found.
Pt(Mo) electrodes showed a higher specific activity in the reaction of methanol oxidation in the potential range of 0.35–0.45
V (RHE) as compared to Pt/Pt. 相似文献
2.
B. I. Podlovchenko T. D. Gladysheva A. Yu. Filatov L. V. Yashina 《Russian Journal of Electrochemistry》2012,48(2):173-180
Specific features of the formation of a Pt(Cu) catalyst by the galvanic displacement of electroplated copper (carbon support)
in a PtCl42− solution are considered. The composition, the structure, and electrochemical properties of Pt(Cu) deposits in different stages
of displacement are studied by a complex of methods (SEM, TEM, XPS, voltammetry, etc.). The gradual formation of a stable
“core(Pt, Cu)-shell(Pt)” structure with the average atomic ratio Pt : Cu ≈ 3 : 1 is observed. The results for PtCl42− are compared with the analogous results for PtCl62− published earlier. Particularly, the reasons for the differences in the steady state potentials established on the Pt(Cu)st/C electrode in the presence of PtCl42− and PtCl62− are discussed. 相似文献
3.
H. J. Lewerenz K. Skorupska M. Aggour T. Stempel J. Grzanna 《Journal of Solid State Electrochemistry》2009,13(2):185-194
Photoelectrochemically prepared nanotopographies on semiconductors are used for realization of nanoemitter solar devices that
are active in the photovoltaic and the photoelectrocatalytic mode. The development of solar devices by a nonlinear electrochemical
process and combined chemical/electrochemical metal deposition is described. Based on this low-temperature scalable approach,
first efficiencies of 7.3% in the photovoltaic mode are reported for the photoelectrochemical solar cell n-Si/SiO2/Pt/I3
−–I−. With p-Si/Pt nanocomposite structures, light-induced H2 evolution is achieved. The surface chemistry and morphology is analyzed by photoelectron spectroscopy (PES), Fourier transform
infrared spectroscopy, and high-resolution scanning electron microscopy. The operational principle of Pt-based nanoemitter
solar devices that use silicon single crystal absorbers is analyzed by Mott–Schottky plots, chronoamperometric profiles, and
PES. Related to simultaneous oxide formation during Pt deposition, evidence for the formation of a metal–oxide–semiconductor
junction is obtained that explains the observed electronic behavior.
Contribution to the Fall Meeting of the European Materials Research Society, Symposium D: 9th International Symposium on Electrochemical/Chemical
Reactivity of Metastable Materials, Warsaw, 17th–21st September 2007. 相似文献
4.
Hydrogen species in both SiO2 and Rh/SiO2catalysts pretreated in different atmospheres (H2, O2, helium or air) at different temperatures (773 or 973 K) were investigated by means of1H MAS NMR. In SiO2 and O2-pretreated catalysts, a series of downfield signals at ∼7.0, 3.8–4.0, 2.0 and 1.5–1.0 were detected. The first two signals
can be attributed to strongly adsorbed and physisorbed water and the others to terminal silanol (SiOH) and SiOH under the
screening of oxygen vacancies in SiO2lattice, respectively. Besides the above signals, both upfield signal at ∼−110 and downfield signals at 3.0 and 0.0 were also
detected in H2-pretreated catalyst, respectively. The upfield signal at ∼−110 originated from the dissociative adsorption of H2 over rhodium and was found to consist of both the contributions of reversible and irreversible hydrogen. There also probably
existed another dissociatively adsorbed hydrogen over rhodium, which was known to be β hydrogen and in a unique form of “delocalized
hydrogen”. It was presumed that the β hydrogen had an upfield shift of ca. −20–−50, though its1H NMR signals, which, having been masked by the spinning sidebands of Si-OH, failed to be directly detected out. The downfield
signal at 3.0 was assigned to spillover hydrogen weakly bound by the bridge oxygen of SiO2. Another downfield signal at 0.0 was assigned to hydrogen held in the oxygen vacancies of SiO2 (Si-H species), suffering from the screening of trapped electrons. Both the spillover hydrogen and the Si-H resulted from
the migration of the reversible hydrogen and the β hydrogen from rhodium to SiO2 in the close vicinity. It was proved that the above migration of hydrogen was preferred to occur at higher temperature than
at lower temperature. 相似文献
5.
Pt/SO4
2−−ZrO2 calcined at 873 K shows the same catalytic activity forn-hexane isomerization as the calcined and reduced sample. A platinum reduction peak did not appear in the TPR profile and
the presence of Pt0 was detected by XPS on the only calcined Pt/SO4
2−−ZrO2. Nevertheless, this calcined material does not show hydrogen chemisorption and cyclohexane dehydrogenation activity. 相似文献
6.
Xiaohuin Liu Yong Guo Wenjie Xu Yanqin Wang Xueqing Gong Yanglong Guo Yun Guo Guanzhong Lu 《Kinetics and Catalysis》2011,52(6):817-822
The influence of the alumina support on the catalytic activity of Pt/Al2O3 catalysts in aqueous phase reforming of ethylene glycol to hydrogen was studied. The catalysts were prepared by impregnation
of γ-, δ-, and α-alumina with H2PtCl6. The highest rate of hydrogen production (452 μmol min−1 g−1) obtained with the Pt/α-Al2O3 catalyst can be related to the highest extent of dispersion of Pt on α-Al2O3. XPS, TEM-EDX and TPR-H2 measurements showed the absence of chloride-containing surface complexes in the Pt/α-Al2O3 catalyst. However, chloride-containing entities were found on the surface of Pt/γ-Al2O3 and Pr/δ-Al2O3 catalysts. When chloride ions are removed chlorinated Pt species facilitate the sintering of Pt crystallites and in this
way affect the extent of Pt dispersion. Moreover, depending upon the particular crystalline form, alumina atoms have different
coordination and alumina surfaces contain varying amounts of OH groups of different nature which affect the interaction between
Pt and the support. 相似文献
7.
BiFeO3 film has been deposited on Pt/Ti/SiO2/Si substrate by a simple sol–gel process annealed at 500 °C. X-ray diffraction analysis revealed that the film was fully
crystallized and no impure phase was observed. Cross-section scanning electric microscopy results indicated that the thickness
was about 600 nm. Large remanent polarization was observed. The double remanent polarization is 95.8 μC/cm2 at an applied field of 800 kV/cm. Intense dielectric dispersion was observed above 100 kHz. At a biased electric field of
167 kV/cm, the leakage current densities were identified as ∼10−5 to 10−4 A/cm2. 相似文献
8.
The rate of substitution of the chloride and aqua moieties from the platinum(II)-amine complexes, viz. [Pt(dien)Cl]Cl(Pt1-Chloro) and [Pt(en)(NH3)Cl]Cl (Pt2-Chloro) and their corresponding aqua analogues, viz. [Pt(dien)(OH2)] (ClO4)2 (Pt1-Aqua) and [Pt(en)(NH3)(OH2)](ClO4)2 (Pt2-Aqua), by a series of neutral and anionic nucleophiles,viz. thiourea (TU), 1,3-dimethyl-2-thiourea (DMTU), 1,1,3,3-tetramethyl-2-thiourea (TMTU), iodide (I−) and thiocyanate (SCN−), was determined under pseudo first-order conditions as a function of concentration and temperature using UV/Visible spectrophotometry
and standard stopped-flow techniques. The observed pseudo first-order rate constants for the substitution reactions obeyed
the simple rate law k
obs = k
2[Nucleophile]. Second-order kinetics and negative activation entropies, ca. −93 J K−1 mol−1 and −71 J K−1 mol−1, for the chloro and aqua complexes respectively, support an associative mode of activation. The rate of substitution of both
the chloro and aqua moieties are observed to decrease with an increase in the steric bulk of the neutral nucleophiles, whilst
rate of substitution by SCN− was observed to be faster than that of I−, in correlation with the observed nucleophilicities of the two nucleophiles. A comparison of the second-order rate constants,
k
2, at 298 K, obtained for the substitution reactions of Pt1and Pt2 shows that an increase in chelation in moving from Pt2 to
Pt1 results in a corresponding increase in the reactivity, by a factor of ca. 3, (28.31 ± 0.15 and 8.02 ± 0.13 m
−1 s−1 for Pt1 and Pt2 respectively, in the case of substitution of the aqua species by TU). Computational analysis of the chloro
complexes, viz. Pt1-Chloro, Pt2-Chloro and [Pt(NH3)3Cl]Cl (Pt3) support this conclusion by demonstrating that the Pt–N bond trans to the leaving group is shortened and that the Pt–Cl bond is lengthened when chelation is increased from Pt3 to Pt1. Consequently,
these results suggest that the increase in reactivity of Pt1 over Pt2, promoted by increased chelation, is as a result of
ground state destabilization. 相似文献
9.
Jifei Jia Jianyi Shen Liwu Lin Zhusheng Xu Tao Zhang Dongbai Liang 《Reaction Kinetics and Catalysis Letters》1998,64(2):255-260
The reduction behavior of silica supported iron and platinum-iron catalysts were studied by combinedin situ temperature programmed reduction (TPR)-M?ssbauer Spectroscopy (MBS). The results indicated that the TPR profiles of the supported
Fe catalysts were different from that of bulk α-Fe2O3. There existed an interaction between the Pt and Fe metals and the SiO2 support for the Pt−Fe/SiO2 catalyst. On the supported iron-containing catalysts, the Fe3+ species were highly dispersed on the SiO2 supported before reduction. No Fe0 and Fe2+ in octahedral vacancy were found in the reduction of SiO2 supported iron-containing catalysts. Addition of Pt to the Fe/SiO2 catalyst could promote the reduction of the iron species. 相似文献
10.
Sensitive fluorescent probes for determination of hydrogen peroxide and glucose based on enzyme-immobilized magnetite/silica nanoparticles 总被引:2,自引:0,他引:2
Qing Chang Lihua Zhu Guodong Jiang Heqing Tang 《Analytical and bioanalytical chemistry》2009,395(7):2377-2385
Sensitive fluorescent probes for the determination of hydrogen peroxide and glucose were developed by immobilizing enzyme
horseradish peroxidase (HRP) on Fe3O4/SiO2 magnetic core–shell nanoparticles in the presence of glutaraldehyde. Besides its excellent catalytic activity, the immobilized
enzyme could be easily and completely recovered by a magnetic separation, and the recovered HRP-immobilized Fe3O4/SiO2 nanoparticles were able to be used repeatedly as catalysts without deactivation. The HRP-immobilized nanoparticles were able
to activate hydrogen peroxide (H2O2), which oxidized non-fluorescent 3-(4-hydroxyphenyl)propionic acid to a fluorescent product with an emission maximum at 409 nm.
Under optimized conditions, a linear calibration curve was obtained over the H2O2 concentrations ranging from 5.0 × 10−9 to 1.0 × 10−5 mol L−1, with a detection limit of 2.1 × 10−9 mol L−1. By simultaneously using glucose oxidase and HRP-immobilized Fe3O4/SiO2 nanoparticles, a sensitive and selective analytical method for the glucose detection was established. The fluorescence intensity
of the product responded well linearly to glucose concentration in the range from 5.0 × 10−8 to 5.0 × 10−5 mol L−1 with a detection limit of 1.8 × 10−8 mol L−1. The proposed method was successfully applied for the determination of glucose in human serum sample. 相似文献
11.
Tzvetanka Boiadjieva Milko Monev Alexander Tomandl Hermann Kronberger Günter Fafilek 《Journal of Solid State Electrochemistry》2009,13(5):671-677
The electrochemical deposition and dissolution of Zn on Pt electrode in sulphate electrolyte was investigated by electrochemical
methods in an attempt to contribute to the better understanding of the more complex Zn–Cr alloy electrodeposition process.
A decrease of the Zn electrolyte pH (from 5.4 to 1.0) so as to minimise/avoid the formation of hydroxo-products of Cr in the
electrolyte for deposition of alloy coatings decreases the current efficiency for the Zn reaction, but the rate of the cathode
reaction increases significantly due to intense hydrogen evolution. The results of the investigations in Zn electrolytes with
pH 1.0–1.6 indicate that Zn bulk deposition is preceded by hydrogen evolution, stepwise Zn underpotential deposition (UPD)
and formation of a Zn–Pt alloy. Hydrogen evolution from H2O starts in the potential range of Zn bulk deposition. Data obtained from the electrochemical quartz crystal microbalance
(EQCM) measurements support the assumption that electrochemical deposition of Zn proceeds at potentials more positive than
the reversible potential of Zn. Anodic potentiodynamic curves for galvanostatically and potentiostatically deposited Zn layers
provide indirect evidence about the dissolution of Zn from an alloy with the Pt substrate. The presumed potential of co-deposition
of Cr (−1.9 V vs. Hg/Hg2SO4) is reached at a current density of about 300 mA cm−2. 相似文献
12.
V. L. Lobachev G. P. Zimtseva E. S. Rudakov 《Theoretical and Experimental Chemistry》2005,41(5):302-309
It was found that nitrite anions are effective activators of hydrogen peroxide in the reaction with diethyl sulfide. The observed
kinetics are consistent with the proposed intermediate formation of peroxynitrous acid (ONOOH). The rate constants for the
reaction of diethyl sulfide Et2S with the acid ONOOH (k0 = 1.8⋅103 L/mol⋅s) and with the anion ONOO− (k− = 6⋅10−2 L/mol⋅s) are respectively 105 and three times higher than with hydrogen peroxide.
__________
Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 41, No. 5, pp. 290–295, September–October, 2005. 相似文献
13.
Jianhui Yan Qiang Liu Luxiong Guan Feng Liang Haojie Gu 《Frontiers of Chemistry in China》2009,4(2):121-126
The Pt-Sr(Zr1 − x
Y
x
)O3 − δ
-TiO2(Pt-SZYT) heterojunction photocatalysts were prepared by a photodeposition method. The composite particles were characterized
by XRD, SEM, UV-Vis DRS, and PL techniques. Photocatalytic hydrogen generation in H2C2O4 aqueous solution under the irradiation of simulated sunlight was used as a probe reaction to evaluate the photocatalytic
activity of the photocatalysts. The effects of the content of Pt loading and the concentration of oxalic acid on the photocatalytic
activity of the catalyst were discussed. The continuous photocatalytic activity of the Pt-SZYT and the relationship between
PL intensity and hydrogen generation were also discussed. The results show that Pt-SZYT catalysts had high photocatalytic
activity of hydrogen generation. The content of Pt loading and the concentration of oxalic acid have important influence on
the photocatalytic hydrogen generation. The optimal loading content of platinum was 0.90 mass%. Under this condition, the
average rate of photocatalytic hydrogen generation was 1.68 mmol·h−1 when the concentration of oxalic acid was 50 mmol·L−1. The higher the photocatalytic activity, the weaker the PL intensity, which was demonstrated by the analysis of PL spectra.
__________
Translated from Acta Chimica Sinica, 2008, 61 (in Chinese) 相似文献
14.
The quantitative incorporation and high dispersion of platinum nanoparticles into MCM-41 has been carried out by the coordination
between Pt(IV) ion and APTMS-anchored MCM-41. Before and after calcination of Pt/APTMS/MCM41 samples, the Pt content in samples
was evaluated from home-made photoacoustic spectrometer (PAS). The PAS bands at 350 nm and 450 nm can be assigned to d–d transition bands of Pt complexes. By increasing the concentration of Pt solution, the PAS intensity of Pt/APTMS/MCM41 was
increased proportionally up to 1.0×10−2 M, and remained constant above 1.0×10−2 M. It can be attributed to the saturation of Pt content within Pt/APTMS/MCM41. The Pt content in the saturated Pt/APTMS/MCM41
was 8.5 wt% (the theoretical value), 9.7 wt% (measured by EDX) and 9.2 wt% (measured by ESCA), respectively. This indicates
that the content of Pt precursor within MCM-41 could be controlled by the concentration of Pt precursor solution. The PAS
intensity of calcined Pt/APTMS/MCM41's in H2 flow was increased up to 1.0×10−2 M and remained nearly constant above 1.0×10−2 M. Therefore, we suggest that the formation of Pt complexes with APTMS-anchored MCM-41 made it possible to incorporate quantitatively
Pt nanoparticles in the range of 0.5–9.2 wt% within MCM-41 channels. 相似文献
15.
V. D. Yagodovskii N. N. Lobanov I. G. Bratchikova N. A. Galimova E. A. Platonov O. V. Eremina 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(10):1701-1706
The kinetics of H2 desorption from the surface of a copper-platinum catalyst deposited on silica gel ([1 wt % Pt + 0.15 wt % Cu]/SiO2) and the kinetics of C6H12 dehydrogenation were studied. The effects of copper introduction in a platinum catalyst on the structural characteristics
of platinum particles, the composition of their surface, and the effects of plasmochemical treatments on these parameters
were studied by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The metal-H atom bond energies (E
Pt-H) and the catalytic activity were found to increase in the presence of Cu. This was explained by the formation of new hydrogen
adsorption centers (due to the Cu+δ adatoms) and catalytic centers composed of Cu+δ adatoms and carbon atoms. The mean diameter of Pt particles (D) increased twofold. The microstresses (ɛ) in the particles increased after the catalyst was treated with glow discharge plasma
in Ar and O2 and with high-frequency plasma in H2 (HF-H2). The observed changes in the bond energy E
Pt-H and kinetic parameters were explained by the increase in microstresses in Pt particles. 相似文献
16.
Rima Tarozaitė Loreta Tamašauskaitė Tamašiūnaitė Vitalija Jasulaitienė 《Journal of Solid State Electrochemistry》2009,13(5):721-731
Platinum–tin complexes were prepared by the reduction of Pt(IV) with Sn(II) in HCl media and studied by light absorption spectrometry,
X-ray photoelectron spectroscopy (XPS), and electron microscopy. The formation of three complexes, H3[Pt(SnCl3)5], H2[Pt(SnCl3)2Cl2], and H2[Pt3(SnCl3)8], depending on HCl and SnCl2 concentrations, has been shown. The glassy carbon (GC) electrode modified in the complexes solutions was found to be an electrocatalyst
for borohydride oxidation in a 1.0-M NaOH solution. Comparison of BH4
− electrooxidation on Pt and on GC modified with platinum–tin complexes has shown that catalytic hydrolysis of BH4
− did not proceed in the latter case in contrast to its oxidation on the Pt electrode, and only direct BH4
− oxidation has been observed in the positive potentials scan. The activity of Pt–Sn complexes for BH4
− oxidation changes with time and eventually decreases due to Sn(II), bound in the complex with Pt(II), oxidation by atmospheric
oxygen. The complexes may be renewed by addition of missing amounts of SnCl2 and HCl. 相似文献
17.
Platinum electrocatalysts for fuel cells based on individual oxides Pt/SnO2 and Pt/TiO2 and their solid solutions Pt/Ti1−x
M
x
O2 (M = Ru, Nb) and Pt/Sn1−x
M′
x
O2−δ(M′ = Sb, Ru) were prepared. The influence of the composition of the oxide supports on the activity of the supported platinum
catalysts in electrooxidation of methanol and hydrogen in the presence of CO was studied. The prepared platinum catalysts
supported on solid solutions of tin dioxide Sn1−x
M
x
O2−δ(M = Sb, Ru; x = 0.4−0.9) and Ti1−x
M
x
O2 (M = Ru, Nb; x = 0.7) exhibited higher tolerance to CO poisoning and higher activities for methanol electrooxidation than commercial Pt,Ru
catalysts on carbon support. The use of the proposed oxide supported catalysts in hydrogen and direct methanol fuel cells
improved their performances in comparison with that for the fuel cells with traditional Pt,Ru catalysts on carbon support. 相似文献
18.
Jian Luo Steven L. Suib Yuji Hayashi Hiroshige Matsumoto 《Research on Chemical Intermediates》2000,26(9):849-874
Plasma-induced water splitting at atmospheric pressure has been studied with a novel fan-type Pt reactor and several tubular-type
reactors: an all-quartz reactor, a glass reactor, and three metal reactors with Pt. Ni, and Fe as electrodes. Reaction products
have been analyzed by using GC (gas chromatography) and Q-MS (quadrupole mass spectrometry). Optical emission spectroscopic
studies of the process have been carried out by employing a CCD (charge-coupled device) detector. Water splitting with tubular
quartz and glass reactors is probably non-catalytic. However, a heterogeneous catalytic function of surface of metal electrodes
has been observed. The variation of hydrogen yield (YH) and energy efficiency (Ee) with operational parameters such as input voltages (Uin), flow rates of carrier gas (FHe), and concentrations of water (CW) has been examined. Plasma-induced water splitting can be described with a kinetic equation of-dCw/dt = kCW
0.2. The rate constants at 3.25 kV are 2.8 × 10−4, 3.5 × 10−3, and 3.4 × 10−2 mol0.8L−0.8 min−1 for tubular glass reactor, a tubular Pt reactor, and a fan-type Pt reactor, respectively. A CSTR (continuous-stirred tank
reactor) and PFR (piston-flow reactor) model have been applied to a fan-type reactor and tubular reactor, respectively. A
mechanism on the basis of optical emission spectroscopic data has been obtained comprising the energy transfer from excited
carrier gas species to water molecules, which split via radicals of HO·, O·, and H· to form H2 and O2. The fan-type Pt reactors exhibit highest activity and energy efficiency among the reactors tested. Higher yields of hydrogen
are achieved at higher input voltages, low flow rates, and low concentrations of water (YH = 78 % at Uin of 3.75 kV, FHe of 20 mL/min, and CW of 0.86 %). The energy efficiency exhibits an opposite trend (Ee = 6.1 % at Uin of 1.25 kV, FHe of 60 mL/min and CW of 3.1 %). 相似文献
19.
Zheng-Yang Zhang Qian-Ming Wang Jian-Zhong Wu Wei-Sheng Cai Yi-Fei Yu 《Chemical Papers》2012,66(3):221-225
A novel terbium 2-hydroxymethyl-benzoimidazole-6-carboxylic acid complex has been designed and unique emission changes to
fluoride anions in comparison with HSO4−, AcO−, Cl−, Br−, and I− were observed. Then, the complex was encapsulated into an inorganic matrix. The novel hybrid material, with strong green
emission was successfully synthesized as an anions receptor in water. More importantly, this hybrid material not only gave
luminescence response to F−, but also to HSO4−. Spectroscopic studies demonstrated that the recognition process for fluoride ions can be mainly ascribed to its hydrogen
bonding interactions with hydrogen bond donor units (NH and OH). In case of hydrogen sulfate, the sensing effects can be probably
attributed to its acidity instead of hydrogen bonding interactions. 相似文献
20.
The effect of the concentration of water on the rate of reduction of molecular nitrogen to hydrazine by niobium(iii) hydroxide in alkaline H2O−MeOH and D2O−MeOD mixtures was studied. In both cases, the reaction rate is maximum when [H2O]=4 mol L−1, and the inverse isotopic effect (K
D/k
H>1) is observed when [H2O]<20 mol L−1. Similar regularity was observed for the reaction of hydrogen elimination. It was found that HD is formed in the H2O−MeOH system in the presence of D2. The conclusion was made that the ratedetermining stage in hydrazine formation is the transfer of a hydride ion to the dinitrogen
molecule coordinated to the binuclear NbIII center. A kinetic scheme satisfactorily explaining the effect of the concentration of water ([H2O]=1.5−49.0 mol L−1) on the reaction rate constant was proposed.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1600–1604, September, 1997. 相似文献