Study On Structure Regulation And Performance Of Nickel BasedComposite Anode For Solid Oxide Fuel Cell

In recent decades,along with the rapid economic development,Solid Oxide Fuel Cell（SOFC）has been favored for its excellent energy conversion efficiency（up to 80%for combined heat and power）,environmental friendliness,high safety performance and strong adaptability.Due to the immaturity of the SOFC process,manufacturing costs and a series of problems to hinder its industrialization.In addition,for low-cost conventional nickel-based anode materials,changes in the length of the Triple-phase Boundaries（TPB）brought about by changes in their micro-structure due to changes in process factors will have a significant impact on the output performance of SOFC single cells.Therefore,in this thesis,Ni O/8mol%Y₂O₃stabilized Zr O₂（Ni O/8YSZ）composite anode materials with different nickel oxide contents were prepared to improve the micro-structure of SOFC anode layer by changing the process conditions such as heat treatment temperature,addition of pore forming agent,and anode layer modification,so as to broaden the three-phase interface region for the purpose of enhancing the electrical output performance of SOFC.The main studies and results are as follows:（1）Preparation of Ni O/8YSZ composite anode powder with different Ni O contents（40wt%,50wt%,60wt%,70wt%）by mechanical ball milling method and the change of heat treatment temperature of the anode layer,by modulating the microscopic morphology of the anode layer,the TPB length is broadened to promote the catalytic cracking of the fuel by the anode layer and enhance the electrochemical performance of SOFC.By comparing the electrochemical test data,The results show that the Ni O/8YSZ composite anode powder prepared by mechanical ball milling mixing has good high temperature compatibility and chemical stability at high temperature.The electrochemical performance of the assembled Ni O/8YSZ|8YSZ|(La_0.75Sr_0.25)_0.95Mn O_3±δ/8YSZ（LSM/8YSZ）single cell was tested at a test temperature of 600-800℃,with humidified hydrogen（3%H₂O）as the anode layer fuel gas and air as the cathode layer oxidizing gas.When the Ni O content was 60 wt%,the heat treatment temperature of the anode layer was at 1300℃,and the test temperature was 800℃,the optimal results of the electrochemical performance of the single cell appeared with the maximum output power density of 0.174 W/cm²and the polarization resistance of 0.277（?）·cm².（2）The Ni O/8YSZ composite anode slurry was prepared by grinding method,in which the pore-forming agent（PMMA）and metal oxide（Cu O,Ce O₂,Al₂O₃,Fe₂O₃）additives could modulate the micro-structure of the anode layer and form different nickel-based alloys in the reducing atmosphere of the anode layer to increase the TPB active sites.By comparing the electrochemical test data,the results showed that under the same test conditions,at an additional addition of 5wt%of PMMA,the addition of Ce O₂partially reduced Ce⁴⁺to Ce³⁺in the reducing atmosphere,turning it into a mixed ion-electron conductor and helping to increase the anode catalytic reaction rate with a maximum power density of 0.190 W/cm²and a polarization resistance of 0.227（?）·cm².After that,the cerium nitrate solution was impregnated with the anode pores by impregnation method,and nano-Ce O₂was attached to the anode structure after sintering to further optimize the anode micro-structure,which was tested to have a maximum power density of 0.205 W/cm²and polarization resistance of 0.156（?）·cm².（3）Ni_1-xZn_xO/8YSZ（x=0.05,0.1,0.15,0.2）composite anode materials were prepared by solid-phase method,and the anode micro-structure was adjusted and the TPB of the anode was broadened by doping the anode with doped metal electronic conductors partially replacing Ni metal.By modifying the composition of the anode catalyst,the catalytic activity and electrochemical reaction rate of the anode towards fuel gas are improved,promoting the overall output performance of SOFC.The results show that the maximum power density of a single cell is 0.198 W/cm²and the polarization resistance is0.172（?）·cm²under the same test conditions when x=0.1.