The power generation efficiency of a small-sized SOFC operating at normal pressures can reach 45%-50%. High-pressure SOFC is combined with a gas turbine, to promote the power generation efficiency up to 70%.

the operating temperature of SOFC is high. Only ceramic materials are used as the catalyst, which do not contain precious metals such as platinum and palladium.

in addition to hydrogen, SOFC can also use methane, natural gas and city gas as a fuel and it is not highly demanding for gas purity.

SOFC power generation system is environmentally friendly, and does not discharge sulfide, nitrogen oxides and solid small particles. Its exhaust contains only water and carbon dioxide, and under the premise of the same power generation, the carbon dioxide emissions is 40% lower than coal-fired power stations.

the exhaust of SOFC is as hot as more than 100℃; the exhaust can be used for heating water, household heat supply, and bath.

SOFC directly converts chemical energy into electricity through electrochemical reactions, without mechanical movement; therefore, it barely produces any noise; the sound volume is similar to that of refrigerators or air conditioners.

As shown in the figure, the oxygen cracks into oxygen atom under the catalytic action of the cathode, and at the same time, the oxygen atom combines with electrons from the external circuit to form oxygen ions. At the operating temperature, the oxygen ions are transferred to the porous anode side through the electrolyte layer by the action of the oxygen partial pressure difference. Here, the hydrogen is catalyzed and cracked by the action of the electrode, to form active hydrogen, and then react with the oxygen ions transferred to generate H2O, and release electrons. The electrons return to the battery cathode via the load through an external circuit, to form a current loop and achieve external power supply.

The key materials of SOFC include electrolyte, anode and cathode. In addition, the assembling of the stack also includes the connecting materials and the sealing materials. The main function of electrolyte is to carry out the conductivity of oxygen ion or proton, and isolate the fuel gas from air or oxygen; the main function of the electrode is to provide an electrochemical reaction field and conduct electrons and ions; the primary role of the connecting materials is to connect the cathode and the anode of adjacent cells and conduct electrons to form the cell stack; the sealing material is used to seal the electrodes and the connecting member, to prevent the fuel gas from having direct contact with air or oxygen.

The mostly studied electrolytes are the fluorite-structured stabilized zirconia-based electrolytes, Sr-doped electrolyte, ceria-based, Sr and Mg-doped perovskite-structured lanthanum gallium Mg (LSGM) electrolyte.

Lanthanum strontium manganate (LSM) is a kind of cathode material having broader applications, with better catalytic activity at high temperatures, but the catalytic activity decreases as the temperature decreases rapidly. The cathode is mainly used in high-temperature fuel cells. The cathode commonly used in low-temperature fuel cells mostly has a perovskite structure, which are mainly ferrite and cobalt salts, such as, iron lanthanum strontium, lanthanum strontium cobalt, samarium cobalt, strontium, iron, cobalt, strontium lanthanum, strontium and barium, cobalt, iron, as well as ions and electrons mixed conducting materials. Compared with the LSM cathode materials, these materials have higher electronic conductivity and ionic conductivity. These materials have high ionic conductivity, electronic conductivity and the catalytic activity for electrochemical oxygen reduction reaction at medium and low temperature; they also have better compatibility with medium/low temperature electrolytes such as GDC and LSGM.

One is the Ca or Sr doped LaCrO3 perovskite ceramic materials, such as, La1-xCaxCrO3 (LCC) and La1-xSrxCrO3 (LSC). The other is metal alloy, such as, stainless steel added with Cr and Ni.

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