Oxygen electrochemical pumping

O.A. Mar ina, V.A. Sobyanin, V.D. Belyaev, and V.N. Parmon, The effect of electrochemical pumping of oxygen on catalytic behaviour of metal electrodes in methane oxidation, in New Aspects of Spillover Effect in Catalysis for Development of Highly Active Catalysts, Stud. Surf. Sci. Catal. 77 (T. Inui, K. Fujimoto, T. Uchijima,... 

Figure 5.39. Characterization of the spillover species by photoelectron spectra of the Ols region taken from a 0.02 pm2 spot on the Pt surface (a) The residual O Is spectrum after the cleaning cycles (b) The Ols spectrum measured in 02 atmosphere (pO2=lxI0 6 mbar) (c) The Ols spectrum obtained during electrochemical pumping in vacuum with UWr = 1.1 V. R1 and R2 are the components which are formed by adsorption from the gas phase and by electrochemical pumping. The fitting components of the residual oxygen are shown with dashed lines. Photon energy = 643.2 eV, T 350-400°C.67 Reprinted with permission from Elsevier Science.

Another type of high temperature solid state O2 sensor that has been developed is based on the principle of electrochemical pumping of oxygen with Zr02 electrolytes. These sensors have higher sensitivity (generally, a first power dependence on Pq) than the Nernst cell and the resistive device and possess a number of other characteristics that make them very promising for many new applications. 

Electrochemical pumps have also been successfully used to promote reactions catalytically. If oxygen is pumped through a zirconia cell into a reaction chamber which is, e.g., filled with hydrocarbons, not only the oxygen that is transferred, reacts. The anode itself can act catalytically. It seems that this so-called NEMCA effect ( Nonfaradaic Electrochemical Modification of Catalytic Activity 51) relies on a hindered surface reaction as a consequence of which the applied potential is translated into a concentration polarization, as reflected by the enrichment of a not fully oxidized oxygen species (e.g., O or O2") at the interface.51"53 For this species, redistribution equilibrium may be assumed that... 

Electrochemical pumps and compressors that is, devices for dosage, separation, compression or removal of oxygen (or hydrogen), according to Faraday s law. The set-up devoted to separate oxygen from air has been also referred to as either the ion transport membrane (ITM) or solid electrolyte oxygen separation (SEOS) [6]. 

These devices are widely used for the control and monitoring of oxygen content in gas mixtures or liquid metals. Usually, the electrochemical pump and oxygen sensor are based on YSZ tubes with platinum electrodes. 

This result indicates that the main reaction site is not inside the YSZ film, but its surface. Therefore, it is likely that the selective oxidation of propene occurred at the Au-YSZ-gas triple phase boundary by the oxygen species pumped electrochemicaUy through the SDC and then the YSZ, as shown in Figure 5. However, it was found that acrylaldehyde selectivity in the case of using YSZ I SDC or YSZ i GDC was stiU lower than that obtained with an electrochemical reactor constructed from YSZ alone, as shown in Table 1. Accordingly, a possible occurring of the propene oxidation at the surface of SDC and/or at the triple phase boundary between Au-SDC-gas cannot be denied in this study. 

An electrochemical cell system with ceria-based solid electrolyte coated wdth YSZ prepared by the spin coating method showed higher selectivity to acrylsildehyde than that with ceria-based solid electrol5rte alone. This may be due to the fact that a film of YSZ on the ceria-based solid electroljde to suppress the complete oxidation of propene. When the YSZ SDC disk was used as an electrolyte membrane, selectivity of the oxidation products did not depend on the thickness of YSZ. This indicates that the selective oxidation of propene occurred at the Au-YSZ-gas triple phase boundary by the oxygen species pumped electrochemicaUy through the ceria-based solid electrolyte and the YSZ. 

High ethylene selectivities (56-71%) were obtained using Ni, Mn, and Ti oxides promoted with LiCl. At 750 °C and P = 0.05 atm, Ti+LiCl gave 83% Cj+ selectivity at 18% conversion. Oxygen was electrochemically pumped through yttria-stabilized zirconia as a... 

The measurements were conducted by applying the cell in oxidic melts containing small and equal molar concentrations of antimonyflll) and antimonyfV) (or arsenic(lll) and arsenic(V)) oxide. The special arrangement used separated the melt essentially from the surrounding atmosphere and allowed electrochemical pumping of oxygen into, and out of, the melt by means of a platinum electrode and a zirconia electrode or the zirconia crucible, which contained the melt and served as the oxide ion-conducting wall [28]. The concentration ratio of the polyvalent ionic species could thus be well adjusted. 

On applying a voltage to the two electrodes, oxygen is pumped from the cathode side to the anode side by electrochemical pumping ... 

In addition to the oxygen separation membranes, the proton conducting membranes can also be applied to reduce NO emission by combining heterogeneous catalysis and solid state electrochemistry. The solid electrolytes in MRs serve to electrochemically control chemisorptive bonds and enhance catalytic activity. Figure 8.10 shows the schematic diagram of a steam electrolysis cell constructed with a proton conductor for reducing NO. Steam is electrolyzed at the anode. It shows the produced H+ is electrochemically pumped to the cathode and reacts with NO to produce Nj and HjO ... 

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