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1.
L. Bultel M. Hénault C. Roux E. Siebert B. Béguin F. Gaillard M. Primet P. Vernoux 《Ionics》2002,8(1-2):136-141
The catalytic activity of polycrystalline Pt deposited on Yttria Stabilized Zirconia (YSZ) for the oxidation of propane to
CO2 can be affected using the effect of Non-faradaic Electrochemical Modification of Catalytic Activity (NEMCA). It was found
that by applying positive overpotentials and thus, supplying O2- onto catalyst surface, up to 3.2-fold increase in the catalytic rate of C3H8 oxidation could be obtained at 365 °C. At 305 °C, no effect was evidenced. Using cyclic voltammetry and impedance spectroscopy,
we have shown the modifications induced by the addition of C3H8 on the kinetics of the 02, Pt/YSZ interface in the temperature range 300–400 °C. A decrease of the coverage of adsorbed oxygen species produced electrochemically
was evidenced as well as a decrease of the oxygen electrode reaction rate under anodic potential.
Paper presented at the 8th EuroConference on Ionics, Carvoeiro, Algarve, Portugal, Sept. 16–22, 2001. 相似文献
2.
The effect of non-Faradaic electrochemical modification of catalytic activity (NEMCA) was investigated for the case of C2H4 oxidation on a Pt polycrystalline catalyst film also acting as a working electrode in a galvanic cell of the type: $$C_2 H_4 ,O_2 ,CO_2 ,H_2 O,Pt|CaZr_{0.9} In_{0.1} O_{3 - \alpha } |Au,C_2 H_4 , O_2 ,CO_2 ,H_2 O$$ In addition to proton conduction, CaZr0.9In0.1O3-α is known to exhibit oxygen and hole conduction. Proton conduction predominates over the temperature range, 380 to 460 °C, of the present investigation. It was found that negative current application, i.e. proton supply to the Pt catalyst film causes up to 500% reversible enhancement to the rate of C2H4 oxidation. The catalytic rate increase is up to 20,000 higher than the rate, -I/F, of proton supply to the catalyst. The observed phenomena are discussed within the framework of previous electrochemical promotion (NEMCA) studies. 相似文献
3.
《Solid State Ionics》2006,177(26-32):2205-2209
The effect of non-faradaic electrochemical modification of catalytic activity (NEMCA effect) or electrochemical promotion (EP) was investigated in the total oxidation of propane on porous Pt and Rh catalyst-electrode films interfaced to 8 mol% Y2O3-stabilized-ZrO2 (or YSZ), in the temperature range 425–520 °C and for sub-stoichiometric O2 to propane ratios. Application of either positive or negative overpotentials resulted in non-faradaic increase of the catalytic rate, by up to a factor of 4 in the case of Rh and by up to a factor of 1350 in the case of Pt. The rate increase observed in the case of Pt is among the highest ones reported so far in NEMCA studies with oxygen ion conductors as active supports. 相似文献
4.
The effect of Non-Faradaic Electrochemical Modification of Catalytic Activity (NEMCA effect) or Electrochemical Promotion
(EP) was used to promote the methane oxidation reaction to CO2 and H2O over Pd polycrystalline films interfaced with yttria-stabilized zirconia in galvanic cells of the type: CH4, O2, CO2, Pd/YSZ/Au, CH4, O2, CO2
It was found that by applying positive potentials or currents and thus, supplying O2− onto the catalyst surface, up to 90-fold increases in CH4 oxidation catalytic rate can be obtained. The induced changes in catalytic rate were two orders of magnitude higher than
the corresponding rate of ion transfer to the catalyst-electrode surface, i.e. faradaic efficiency Λ values above 100 can
be attained. The reaction exhibits electrophobic behavior under the experimental conditions of the investigation. The results
can be rationalized on the basis of the theoretical considerations invoked to explain NEMCA behavior, i.e. the effect of changing
work function on chemisorptive bond strengths of catalytically active electron donor or acceptor adsorbates.
Paper presented at the 5th Euroconference on Solid State Ionics, Benalmádena, Spain, Sept. 13–20, 1998. 相似文献
5.
The silver-catalyzed epoxidation of ethylene is a reaction of great technological importance and also represents one of the
most challenging and thoroughly studied catalytic systems.
It was found that the catalytic activity and selectivity of polycrystalline Ag for the epoxidation and complete oxidation
of ethylene can be affected in a pronounced and reversible manner by electrochemically supplying or removing oxygen ions O2- or Na+ to or from the silver catalyst surface in ZrO2 (8 mol%Y2O3) or β″-Al2O3 solid electrolyte cell reactors and in the presence or absence of traces of chlorinated hydrocarbons in the gas phase.
The steady-state changes in catalytic rates of formation of C2H4O and CO2 are typically 10 to 100 times larger than the corresponding rate of ion transport to or from the catalyst surface, i.e.,
the reaction exhibits the effect of Non-Faradaic Electrochemical Modification of Catalytic Activity (NEMCA) or “Electrochemical
Promotion”. The selectivity to C2H4O can be very significantly altered, relative to open circuit conditions.
Under fuel rich conditions, temperatures near 250°C and in the presence of traces of 1,2-C2H4Cl2 in the gas phase selectivity values as high as 88% can be obtained, well above the ones reported in the open literature.
The observed phenomena are discussed and interpreted within the framework of previous NEMCA studies and the currently prevailing
ideas regarding the mechanism of ethylene epoxidation.
Paper presented at the 1st Euroconference on Solid State Ionics, Zakynthos, Greece, 11 – 18 Sept. 1994 相似文献
6.
M. Marwood S. Balomenou A. Tsiliras C. A. Cavalca C. Pliangos C. G. Vayenas 《Ionics》1998,4(3-4):207-214
In this paper we discuss the first attempts to induce the effect of Electrochemical Promotion or Non-Faradaic Electrochemical Modification of Catalytic Activity (NEMCA) on highly dispersed catalyst-electrodes systems which can compete in terms of dispersion and surface area with industrial catalysts. Three systems are discussed:
- Electrochemical promotion of C2H4 oxidation on electronically isolated Pt catalysts on Y2O3-stabilized-Zirconia (YSZ) where NEMCA is induced via potential application between two terminal Au electrodes also supported on the solid electrolyte (bipolar design).
- Electrochemical promotion of C2H4 oxidation on a finely dispersed Pt catalyst deposited on a Au electrode which is supported on YSZ.
- Induction of NEMCA during CH3OH oxidation on Pt without external voltage application by utilizing the potential difference developed between the catalyst and a catalytically inert counter electrode.
7.
B. Béguin F. Gaillard M. Primet P. Vernoux L. Bultel M. Hénault C. Roux E. Siebert 《Ionics》2002,8(1-2):128-135
The reduction of NO by C3H6 in the presence of oxygen, is of great environmental importance. Platinum-based catalysts are very active but not selective
towards N2 production and mainly convert NO into N2O, which participates to the greenhouse effect. Moreover, their operating temperature window is quite narrow. Electrochemical
promotion was used to improve platinum catalytic behaviour. Platinum was deposited on YSZ (Y2O3 — stabilised ZrO2), an O2-conductor. It was found that a negative current increased the rate of NO reduction and CO2 formation. This rate enhancement was non-Faradaic with an apparent Faradaic efficiency (Λ) close to 180 indicating the manifestation
of a NEMCA effect. However, the current application had no effect on the N2 selectivity
Paper presented at the 8th EuroConference on Ionics, Carvoeiro, Algarve, Portugal, Sept. 16–22, 2001. 相似文献
8.
This study deals with the relationship between open-circuit potential and catalytic activity of the system Pt/YSZ. Temperature-programmed
desorption (TPD) of oxygen was carried out in order to investigate the link between the oxygen coverage and the potential.
Then, catalytic activity in parallel with the potential value was measured between 200 °C and 500 °C for NO oxidation, C3H8 combustion, C3H6 combustion and the selective catalytic reduction (SCR) of NO by C3H6 in the presence of oxygen. It was found that potential measurement can give precious information on the competitive adsorption
between oxygen and other reactants. Finally, it seems to be also a good way to anticipate the NEMCA behavior for reactions,
which involve oxygen.
Paper presented at the Patras Conference on Solid State Ionics — Transport Properties, Patras, Greece, Sept. 14 – 18, 2004. 相似文献
9.
The catalytic oxidation of methane on polycrystalline palladium films was studied at 550-750°C and atmosheric total pressure.
The reaction was studied under both open and closed-circuit. Under open circuit, and when yttria-stabilized zirconia (YSZ)
was used as solid electrolyte, the technique of Solid Electrolyte Potentiometry (SEP) was used to monitor the thermodynamic
activity of oxygen adsorbed on the Pd electrode during reaction. The main products were those of complete oxidation, i.e.
CO2 and H2O. Under closed-circuit, the effect of electrochemical oxygen “pumping” to or from the catalyst was studied. Non-faradaic
(NEMCA) phenomena were observed but the reaction rate enhancement factors (A) were not as large as with previously studied
catalytic systems.
Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Italy, Sept. 15–22, 1996. 相似文献
10.
S. Peng-ont S. Souentie S. Assabumrungrat P. Praserthdam S. Brosda C. G. Vayenas 《Ionics》2013,19(12):1705-1714
The effect of electrochemical promotion of catalysis was investigated for the oxidation of propane using Pd, Ir, and Ru catalyst-electrodes sputter-deposited on YSZ disks in the temperature range of 250–450 °C. Electrophobic type behavior was observed, i.e., the catalytic reaction rate was found to increase with catalyst potential. The observed rate changes under polarization were strongly non-Faradaic and exceeded under anodic potential application the electrocatalytic rate of O2? supply to the catalyst surface, I/2F, by up to a factor of 250 for Pd, 125 for Ir, and 15 for Ru catalyst-electrodes. 相似文献
11.
The catalytic and the electrocatalytic behavior of MnOx oxides deposited on Yttria Stabilized Zirconia (YSZ) in the form of thin porous films, was studied during the reaction of
methane activation at high methane to oxygen ratios. Experiments were carried out in a continuous flow well-mixed reactor
(CSTR), at atmospheric total pressure and in a temperature range between 500–850 °C. It was found that the electrochemical
pumping of oxygen anions (O2−) through the solid electrolyte (YSZ) affect drastically the rates of CO2, C2H4 and C2H6 formation and consequently the C2 selectivity.
Paper presented at the 4th Euroconference on Solid State Ionics, Renvyle, Galway, Ireland, Sept. 13–19, 1997 相似文献
12.
The selective catalytic reduction of NO by propylene or CO in the presence of excess oxygen is a system of great technological
importance. The effect of Electrochemical Promotion (or Non-faradaic Electrochemical Modification of Catalytic Activity —
NEMCA) was used to promote this reaction (C3H6 or CO/NO/O2) on Rh/YSZ catalyst-electrodes.
It was found that both the catalytic activity and the selectivity of the Rh catalyst-electrode is affected dramatically upon
varying its potential with respect to a Au pseudoreference electrode. Catalytic rate enhancements up to 15000% and 6000% were
observed in the case of NO reduction by propylene, while the product selectivity to N2 production is affected significantly (up to 200%) upon positive potential application. Remarkable promotion of the catalytic
activity was also observed in the case of NO reduction by CO, since up to 20-fold increases both in catalytic rates and in
NO conversion were obtained under NEMCA conditions.
Paper presented at the 6th Euroconference on Solid State Ionics, Cetraro, Calabria, Italy, Sept. 12–19, 1999. 相似文献
13.
Solid electrolytes can be used as active catalyst supports to induce significant and reversible catalytic activity and selectivity enhancement via the effect of Non-Faradaic Electrochemical Modification of Catalytic Activity (NEMCA effect) or Electrochemical Promotion which has been recently reported for over fourty catalytic reactions. Atomically resolved Scanning Tunneling Microscopy was used to image the reversible electrochemically controlled dosing (backspillover) of sodium on Pt(111) interfaced to β″-Al2O3 at atmospheric pressure, which has been proposed as the cause of the NEMCA effect in the case of Na+ conductors. It was found that electrical current application between the Pt(111) monocrystal and a counter electrode also in contact with the β″-Al2O3 Na+-conducting solid electrolyte causes reversible migration (backspillover and spillover) of sodium which forms a (12×12) hexagonal structure on the Pt(111) surface. In addition to explaining the phenomenon of Electrochemical Promotion in Heterogeneous Catalysis when using Na-β″-Al2O3 solid electrolyte these observations provide the first STM confirmation that:
- spillover-backspillover phenomena can take place over enormous (~mm) atomic distances, and
- promoters can form ordered structures on catalyst surfaces under ambient conditions relevant to industrial practice.
14.
《Solid State Ionics》2004,166(1-2):183-189
The Pt/yttria-stabilized cubic zirconia (YSZ) interface exposed to a reactive gas was characterised by solid electrolyte potentiometry and cyclic voltammetry. The catalytic reactions included total combustion of C3H8 and C3H6 to CO2 and H2O as well as NO reduction by C3H6 in the presence of O2 under oxygen-rich and stoichiometric conditions. The solid electrolyte potentiometry as a function of the temperature in C3Hx/O2 (with x=6 or 8) reflected the catalytic properties of Pt for C3Hx oxidation. In C3H6/NO/O2, the reduction of NO was evidenced below 300 °C. The cyclic voltammetry evidenced the formation of an oxygen chemisorbed layer on the Pt surface under anodic potential. Propane had no effect on this chemisorbed layer, whereas propene weakened significantly the strength of this Pt–O bond. Addition of NO to C3H6/O2 led to the disappearing of this chemisorbed layer. The use of solid electrolyte potentiometry in conjunction with cyclic voltammetry allowed us to determine the surface oxidation state of Pt during the catalytic reactions. 相似文献
15.
C. Athanasiou G. Marnellos J. E. ten Elshof P. Tsiakaras H. J. M. Bouwmeester M. Stoukides 《Ionics》1997,3(1-2):128-133
The catalytic and electrocatalytic behaviour of the La0.6Sr0.4Co0.8Fe0.2O3 (LSCF) perovskite deposited on yttria stabilized zirconia (YSZ), was studied during the reaction of methane oxidation. Experiments
were carried out at atmospheric pressure, and at temperatures between 600 and 900 °C. When, instead of cofeeding with methane
in the gas phase, oxygen was electrochemically supplied as O2−, considerable changes in the methane conversion and product selectivity were observed. The non-faradaic effects (NEMCA) were
also studied and compared to those observed with metal catalysts.
Paper presented at the 4th Euroconference on Solid State Ionics, Renvyle, Galway, Ireland, Sept. 13–19, 1997 相似文献
16.
《Current Applied Physics》2009,9(1):172-178
Recovery properties after H2S catalytic poisoning of catalytic-type gas sensor with photo-catalysts and UV radiation have been examined. Each sensing material of the sensor consists of Pd, Pt supported on γ-Al2O3 and Pd/titanate, Pt/titanate nanotubes or TiO2 particles. Pd/titanate and Pt/titanate nanotubes photo-catalyst were synthesized by hydrothermal synthesis method. All the sensors were deactivated after 500 ppm H2S exposure for 20 h. The sensors with Pd/titanate or Pt/titanate nanotubes showed regenerated voltage response under UV radiation. However the sensor with TiO2 particles showed negligible regenerated voltage response. Regenerated voltage response with Pd/titanate or Pt/titanate nanotubes may stem from location of Pd or Pt catalyst on the titanate nanotube photo-catalyst. 相似文献
17.
A. Giannikos P. Petrolekas C. Pliangos A. Frenzel C. G. Vayenas H. Pütter 《Ionics》1998,4(3-4):161-169
The effect of Non-Faradaic Electrochemical Modification of Catalytic Activity, orin-situ controlled promotion, was investigated during Acetylene selective hydrogenation on Pd films deposited on β″ - Al2O3, a Na+ conductor, at temperatures from 60 to 100 °C and GHSVs from 103 to 104 h-−1, i.e., under conditions similar to those used in industrial processes. It was found that both acetylene conversion and hydrogenation
selectivity can be affected by means of externally applied potentials, i.e., by supplying or removing sodium ions to or from
the catalyst surface. Electrochemical sodium supply to the Pd catalyst surfaċe was found to supress both the rate of acetylene
hydrogenation and, to a larger extent the rate of ethylene hydrogenation to ethane. Consequently electrochemical sodium supply
was found to enhance the selectivity to ethylene. Thus, β″ - Al2O3 can act as an active catalyst support causing enhanced performance of the Pd catalyst. Acetylene conversion and hydrogenation
selectivity values up to 90 % and 95 %, respectively, were obtained.
Paper presented at the 5th Euroconference on Solid State Ionics, Benalmádena, Spain, Sept. 13–20, 1998. 相似文献
18.
A. Saramat M. Andersson S. Hant P. Thormählen M. Skoglundh G. S. Attard A. E.C. Palmqvist 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):209-211
Conventional Pt/Al2O3 catalysts prepared by wet-impregnation are
composed of Pt nanoparticles exposing convex and facetted surfaces deposited
on high-surface area γ-Al2O3 supports. A hexagonal phase
mesoporous Pt material (denoted H1-Pt) prepared by chemical reduction
in the aqueous domains of a lyotropic liquid crystalline template exposes
however mainly a concave surface with expected different catalytic
properties. A series of Pt/Al2O3 catalysts were prepared using
H1-Pt, Pt-black or wet-impregnated Pt, and the samples were
characterized by SEM-EDX and TEM, and finally evaluated for CO oxidation.
The H1-Pt/Al2O3 catalyst showed an ignition profile for CO
oxidation at lower temperatures and thus appeared less sensitive to CO
poisoning than the two other types of samples. This difference may be
related to the differences in surface curvature. 相似文献
19.
《Solid State Ionics》2006,177(26-32):2221-2225
Scanning tunneling microscopy (STM) was used to investigate the surfaces of Pt(111) single crystals interfaced with YSZ and β″-Al2O3 at atmospheric pressure. In both cases the STM imaged the reversible electrochemically controlled dosing (backspillover) of O2− species and of Na+ species on Pt(111) surface respectively, which both form a (12 × 12) hexagonal structure on the Pt(111) surface. On the mechanistic side, the STM has confirmed the backspillover mechanism of electrochemical promotion and metal support interactions. 相似文献
20.
Yuhai Hu 《Surface science》2007,601(21):5002-5009
The influence of pre-dosed O2 on the catalytic reduction of NO with 13C2H5OH on the surface of stepped Pt(3 3 2) was investigated using Fourier transform infra red reflection-absorption spectroscopy (FTIR-RAS) and thermal desorption spectroscopy (TDS). We show that the oxidation of 13C2H5OH with O2 is a very effective reaction, occurring at 150 K and giving rise to acetate. The presence of NO does not lead to any evident oxidation of 13C2H5OH irrespective of the annealing temperature. For the case of O2 + 13C2H5OH + NO co-adlayers, oxidation of 13C2H5OH also takes place at 150 K. However, no new surface species that are supposed to be an intermediate for the production of N2 are detected.The influence of O2 on the production and desorption of N2 is intimately related to both O2 and 13C2H5OH coverage. The presence of pre-dosed O2 does not greatly promote N2 desorption. In fact, N2 desorption is suppressed quantitatively with increasing O2 coverage, after which unreacted, or left-over O atoms appear and remain on steps. It is concluded that the presence of pre-dosed O2 does not play a role of activating reactants in the catalytic reduction of NO with 13C2H5OH on the surface of Pt(3 3 2). 相似文献