x y SOFCs and this is currently the main development    challenge。

CxHy þ 2 O2 ! xCO þ 2 H2 ð1Þ

The reaction (1) in the vicinity of anode provides significant drop of the oxygen partial pressure。 If in the vicinity of cathode there is no oxidation of hydrocarbons, what can be controlled by catalytic activity of cathode, then the oxygen partial pressure is high and fixed by the hydrocarbon/air ratio。 Usually, oxygen partial pressure in the vicinity of cathode is

1。1atm, while in the vicinity of the anode it drops down to 10218 atm。 This difference in oxygen partial pressures causes the formation of chemical potential gradient in the electrolyte, which is compensated by the electric field。 When  the electrodes are connected by an external circuit, the electric current can continuously flow due to oxygen ions transport in the electrolyte, electrochemical reaction  (2)  at  the  cathode and electrochemical reactions (3) and (4) at the anode:文献综述

Figure 8 Conductivity of nanocrystalline samarium doped ceria electrolyte

Depending on the way of the electrode placement on the electrolyte the SC-SOFC are recognized as conventional or planar。 The conventional configuration is virtually the same as in case of the conventional double chamber SOFC。 In contrast, the planar structure of SC-SOFC is unknown from the conventional SOFC design and especially interesting for miniaturization。 In the planar design both electrodes are placed on the same side (face) of an electrolyte。 Figure 9 shows schematic illustration of the planar design and diagram of fuel cell operation。 This design has an advantage over conventional structure as the thickness of the electrolyte does not influence the SC-SOFC performance。 Instead, the performance depends on the anode and cathode spacing (distance “a” in the Figure 9), because it reflects the Ohmic resistance of the cell。 If the spacing “a” is smaller then the resistance of the fuel cell is lower。 However, the laminar flow requirement should be fulfilled for the best SC-SOFC performance and therefore, it can be expected that placing the electrodes to close to each other (,50 mm) can result in the lower fuel cell performance。

An example of SC-SOFC planar structure is shown in Figure 10。 The SC-SOFC is fabricated with an interdigitated anode and cathode structures on the same side of the electrolyte via a microfluidic lithography technique (Ahn et al。, 2006a, b)。

grain size 40nm grain size 55nm

solid symbol -grain conductivity

open symbol - grain boundary conductivity

1。8 2。0 2。2 2。41000/T [1/K]

Vacuum-assisted infiltration of the well-dispersed suspensions to the microchannels generated by the contact of polydimethylsiloxane (PDMS) molds to the electrolyte (YSZ) surface is used。 This allows simple micropatterning of the ceramics with complex structures in a relatively large area in a short time。 Unlike thin film deposition and MEMS techniques the fabrication method was based on colloidal ceramic processing。  The  anode  suspension  (Ni-Sm0。2Ce0。8O2)  of 200 m L is dropped into a reservoir accessing the microchannel of the mold and then evacuated in the vacuum chamber。 Upon restoring the atmospheric pressure, the anode suspension is fully infiltrated into the microchannel by an induced pressure difference。 After the infiltration the microfluidic device is dried and the PDMS mold is peeled off from the electrolyte。 Next, the structure is sintered using the来,自.优;尔:论[文|网www.youerw.com +QQ752018766-

same method the cathode (La0。8Sr0。2MnO3) is fabricated。 The size of obtained structure is of about 5 £ 5 mm2 with electrode-