Ceria solid electrolyte

Gadolinia-ceria, solid electrolyte, 93, 526 Galvani potential, 203, 215 Gauss law, 214 Gold... 

A signihcant problem in tire combination of solid electrolytes with oxide electrodes arises from the difference in thermal expansion coefficients of the materials, leading to rupture of tire electrode/electrolyte interface when the fuel cell is, inevitably, subject to temperature cycles. Insufficient experimental data are available for most of tire elecuolytes and the perovskites as a function of temperature and oxygen partial pressure, which determines the stoichiometty of the perovskites, to make a quantitative assessment at the present time, and mostly decisions must be made from direct experiment. However, Steele (loc. cit.) observes that tire electrode Lao.eSro.rCoo.aFeo.sOs-j functions well in combination widr a ceria-gadolinia electrolyte since botlr have closely similar thermal expansion coefficients. 

Electrochemical Promotion of Particulate Matter (Soot) Combustion Using a Ceria-Gadolinia Solid Electrolyte and a Dispersed Perovskite Catalyst... 

Sol-gel technique has been used to deposit solid electrolyte layers within the LSM cathode. The layer deposited near the cathode/electrolyte interface can provide ionic path for oxide ions, spreading reaction sites into the electrode. Deposition of YSZ or samaria-doped ceria (SDC, Smo.2Ceo.8O2) films in the pore surface of the cathode increased the area of TPB, resulting in a decrease of cathode polarization and increase of cell performance [15],... 

Inaba, H. Tagawa, H. 1996. Ceria-based solid electrolytes. Solid State Ionics 83 1-16. 

A key factor in the possible applications of oxide ion conductors is that, for use as an electrolyte, their electronic transport number should be as low as possible. While the stabilised zirconias have an oxide ion transport number of unity in a wide range of atmospheres and oxygen partial pressures, the BijOj-based materials are easily reduced at low oxygen partial pressures. This leads to the generation of electrons, from the reaction 20 Oj + 4e, and hence to a significant electronic transport number. Thus, although BijOj-based materials are the best oxide ion conductors, they cannot be used as the solid electrolyte in, for example, fuel cell or sensor applications. Similar, but less marked, effects occur with ceria-based materials, due to the tendency of Ce ions to become reduced to Ce +. 

Marko Hrovat, Ariane Ahmad-Khanlou, Zoran Samadzija, Janez Hole, Interactions between lanthanum gallate based solid electrolyte and ceria , Materials Research Bulletin, 34[12/13], 2027-2034 (1999). 

K. Eguchi, T. Hatagishi, and H. Arai, Power generation and steam electrolysis characteristics of an electrochemical cell with a zirconia- or ceria-based electrolyte, Solid State Ionics, 86-8 1245-1249 (1996). 

Hidenori, Y. et al.. High temperature fuel cell with ceria-yttria solid electrolyte, J. Electrochem. Soc. Solid-State Sci. Technol., 2077-2080 (1988). 

Kirk, T.J. and Winnick, J., A hydrogen sulfide solid-oxide fuel cell using ceria-based electrolytes, J. Electrochem. Soc., 140, 3494-3496 (1993). 

Figure 9.4 Total conductivity of stabilized zirconia (a) and doped ceria (b) solid electrolytes [34—40], compared to the oxygen ionic conductivity of pyrochlore-type Cd2Zr2O7 5 [41], (Cd,Ca)2Ti2O7 5 [42], (Cd,Ca)2Sn2O7 s [43], and 241707 a [44].

Characterization of the ceria-based solid electrolyte coated with YSZ... 

We have studied the partial oxidation of hydrocarbons with electrochemical reactor using an oxide ionic conductor, e.g. YSZ, SDC, etc. [2-4, 10]. In these studies, it was found that a ceria-based solid electrolyte is useful for the propene oxidation to acrylaldehyde at relatively low temperature of 350°C [10]. In this case, however, the acrylaldehyde selectivity was lower than that obtained with the electrochemical reactor constructed from YSZ. This may be due to the high activity of ceria surface for the complete oxidation of hydrocarbons [13,14]. 

The effect of the YSZ coating on the ceria-based solid electrolyte was shown in Table 1. When the YSZ I SDC membrane was used as the solid electrolyte, selectivities to acrylaldehyde (Scho) carbon monoxide (Sco) and carbon dioxide (Scoa) based on converted propene was 13.4%, 25.6% and 61%, respectively. Here, it should be emphasized that the selectivity to acrylaldehyde increased with YSZ coating compared with that (Scho =8.5 %) obtedned by using SDC alone as a solid electrolyte. In addition, it was found that carbon monoxide formation was observed in the present study, although its formation was not detected in the case of SDC alone. The same phenomena were observed, when the Gd doped... 

In order to clarify the reaction site of the partial oxidation of propene using the ceria-based solid electrolyte coated with YSZ as a membrane, we have studied the dependence of the selectivities to oxygenates on the thickness of YSZ. When the Sm doped ceria coated with YSZ (YSZ SDC), each selectivity of the oxidation products did not dependent on the thickness of YSZ, as shown in Figure 4. 

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. 

Yttria-doped zirconia and gadolinia-doped ceria oxygen ion conductors and strontium yttrium zirconium oxide proton conductors are being investigated as the solid electrolyte. 

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