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•Porous Ru catalyst films were deposited on BZY proton conducting support.•The selectivity of CO2 hydrogenation to CH4 on Ru is significantly enhanced via EPOC.•Proton removal from ...the catalyst enhances methanation and suppresses CO formation.•Selectivity to CH4 varies between 15% and 65% upon varying the catalyst potential.•The apparent Faradaic efficiency of methanation reaches values up to 500.
The kinetics and the electrochemical promotion of the hydrogenation of CO2 on polycrystalline Ru deposited on BZY (BaZr0.85Y0.15O3−α+1wt% NiO), a proton conductor in wet atmospheres, with α≈0.075, was investigated at temperatures 300–450°C and atmospheric pressure. Methane and CO were the only detectable products and the selectivity to CH4 could be reversibly controlled between 15% and 65% by varying the catalyst potential by less than 1.2V. The rate and the selectivity to CH4 are very significantly enhanced by proton removal from the catalyst via electrochemically controlled spillover of atomic H from the catalyst surface to the proton-conducting support. The effect is strongly non-Faradaic and the apparent Faradaic efficiency of methanation takes values up to 500 and depends strongly on the porous Ru catalyst film thickness. The observed strong promotional effect, in conjunction with the observed reaction kinetics, is in good agreement with the rules of electrochemical and chemical promotion.
In this study, we have investigated, for the very first time, the oxygen electrode reactions on Ag/YSZ electrochemical catalysts both in oxygen and under reaction conditions compatible with the ...ethylene epoxidation reaction. Electrochemical Impedance Spectroscopy (EIS) in combination with in-situ Raman spectroscopy and catalytic activity measurements were used to identify and understand the main oxygen reaction pathways. The results obtained suggested that the rate limiting step under an O2 reaction atmosphere (at 300 °C) is the O2 adsorption/dissociation process on the Ag catalyst-electrode. In addition, the polarization resistance increased with time under the presence of O2. This was attributed to the formation of Ag2O on the catalyst surface or near surface, which limits the oxygen electrode reactions. Finally, we observed that the addition of ethylene in the feed stream hinders the electrode reaction, due to its competitive chemisorption with oxygen on Ag. These results give new insights into the design of selective Ag/YSZ catalyst for ethylene epoxidation.
•Oxygen electrode mechanism on Ag/YSZ investigated under ethylene epoxidation conditions.•Oxygen electrode reaction limited by oxygen chemisorption on Ag.•Ag2O species can be stabilized at 300 °C.•New insights for designing active electro-promoted Ag/YSZ catalysts for ethylene epoxidation.
The kinetics and the electrochemical promotion of the hydrogenation of CO2 to CH4 and CO are compared for Ru porous catalyst films deposited on Na+, K+, H+ and O2− conducting solid electrolyte ...supports. It is found that in all four cases increasing catalyst potential and work function enhances the methanation rate and selectivity. Also in all four cases the rate is positive order in H2 and exhibits a maximum with respect to CO2. At the same time the reverse water gas shift reaction (RWGS) which occurs in parallel exhibits a maximum with increasing pH2 and is positive order in CO2. Also in all cases the selectivity to CH4 increases with increasing pH2 and decreases with increasing pCO2. These results provide a lucid demonstration of the rules of chemical and electrochemical promotion which imply that (∂r/∂Φ)(∂r/∂pD)>0 and (∂r/∂Φ)(∂r/∂pA)<0, where r denotes a catalytic rate, Φ is the catalyst work function and pDandpA denote the electron donor and electron acceptor reactant partial pressures respectively.
Effect of Ru catalyst support and potential on product selectivity. Display omitted
•Porous Ru catalyst films were deposited on O2−, H+, Na+ and K+ conducting supports.•The kinetics and EPOC behavior of CO2 hydrogenation on these catalysts were compared.•Positive potential enhances the selectivity to CH4 for all supports.•With K+, CH4 selectivity varies between 0% and 98% upon varying catalyst potential.•All results conform to the rules of promotion and electrochemical promotion (EPOC).
Abstract
Within the frame of the EKATϒ programme, whose purpose is the innovative imaging of the subsurface of archaeological sites and the interior of structural elements of monuments in “three” and ...“four” dimensions, the applicability of Muon Tomography technique in the representation of a tumulus is tested in the present work. The scanning of its internal structure is accomplished by measuring the flux deficit of cosmic muon tracks in the presence of an object inside the tumulus, compared to the muon flux when traversing a uniform tumulus (transmission muography). The feasibility study of the method is achieved with a simulation of the tumulus geometry and the structure under investigation. Following the simulation process, a tracking telescope, consisting of four MicroMegas detectors and two trigger plastic scintillators, will be placed near Apollonia’s tumulus to collect data. For the specific latitude where the Apollonia’s tumulus is located, the energy and angular muon distribution at sea level is studied. Implementing the dimensions of the telescope in the simulation, the back-projection method is examined for the localization of the hidden object and the estimation of its dimensions. The method is tested for the telescope optimal position, placed under the tumulus, and the realistic one, placed near the tumulus at the level of its base.
Among the neurological manifestations of systemic lupus erythematosus (SLE), chorea is rare, presenting in less than 7% of the pediatric SLE patients. It can appear early in the onset of SLE, be the ...first or even the sole clinical feature of the illness and has strongly been associated with the presence of antiphospholipid antibodies. We report on the case of a 13-year old boy, admitted with acute onset chorea and finally diagnosed with SLE. Subsequently, we present a short review of the literature on the epidemiology, suggested pathogenesis, clinical presentation and treatment of this rare presentation of SLE.
Summary
Erectile dysfunction (ED) is a complex disorder with various biopsychosocial implications leading the individual into a state of chronic stress that further worsens ED symptoms. The aim of ...this study is to investigate the effects of a 8‐week stress management programme on erectile dysfunction (ED). A convenience sample of 31 newly diagnosed men with ED, aged between 20 and 55 years, was recruited during a period of 5 months to receive either tadalafil (12 patients) or tadalafil and the 8‐week stress management programme. Both groups showed statistical significant improvement of both perceived stress and erectile function scores. Men practising stress management showed a statistical significant reduction in perceived stress score compared with men receiving tadalafil alone. No other statistical significant differences were noted between the two groups, although the stress management group showed a lower daily exposure to cortisol compared with the control group after 8 weeks. Finally, perceived stress and cortisol showed some interesting correlations with sexual function measurements. These findings provide important insight into the role of stress management, as part of the recommended biopsychosocial approach, in ED. Future studies should focus on randomised, controlled trials with larger samples and longer follow‐up time.
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•Pd nanoparticles supported on Co3O4 have been promoted via EPOC for CH4 oxidation.•Positive potential enhances the catalytic rate of the supported catalyst by 250%.•The Co3O4 support ...is a mixed electronic/ionic conductor at elevated temperatures.•Nanodispersed catalysts are partly promoted via the EPOC ion migration mechanism.
During the last two decades the Electrochemical Promotion of Catalysis (EPOC) phenomenon has been studied extensively for many catalytic reactions including hydrocarbon oxidation reactions and hydrogenations. In the majority of the studies, the catalysts/electrodes consisted of porous noble metal films (Pt, Pd, Rh) prepared, for instance, by calcination of organometallic pastes. This results in low metal dispersion and low active surface area, limiting therefore the overall catalytic activity. In view of further practical application of the EPOC phenomenon to industrial catalysts, we should be able to enhance the activity of nanodispersed materials. In this study, for the very first time, we observed an enhanced catalytic activity of a Pd nanodispersed catalyst supported on a porous Co3O4 semiconductor film. The Pd/Co3O4 composite powder was deposited on an yttria-stabilized zirconia (YSZ) solid electrolyte without the presence of an interlayer film. The observed enhancement was non-Faradaic, with Faradaic efficiency values as high as 80. The Pd/Co3O4 catalyst was characterized thoroughly by means of a wide variety of physicochemical techniques, such as TEM, SEM, TGA, ICP and BET. In addition, this material was further compared with a classical Pd/YSZ metallic film, prepared by calcination of an organometallic paste. This allows for a comparison of metal-support interactions (MSI) and the EPOC effect. Using supported catalysts as catalytic films for electrochemical promotion studies may lead to the practical utilization of EPOC in the chemical industry or in gas exhaust treatment.
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