Application Of Semiconductor Heterogeneous Nanocomposite For Solid Oxide Fuel Cells

Solid oxide fuel cell（SOFC）,as an energy conversion device from chemical energy into electrical energy directly,has attracted much attention due to its low emissions and high efficiency.Currently,the commercialization of SOFCs is limited by the high temperature requirements of electrolytes,such as the typically Y₂O₃-stabilized Zr O₂（YSZ）,which can achieve high ionic conductivity(>0.1 S cm^-1)at high temperatures（～1000℃）.However,high operating temperatures lead to performance degradation and cost increase.It is a challenge to develop electrolytes with high ionic conductivity at low temperatures（<600℃）.In recent years,semiconductor heterostructured composites with high ionic conductivity have received much attention.In this paper,based on p-n junction and Schottky heterojunction,high-performance semiconductor heterocomposite electrolytes are designed:（1）P-n junction form a built-in electric field through the mutual contact of semiconductors with different work function and the migration of carriers,and shows good performance when applied to the electrolyte of the LT-SOFC.Based on p-type CuFeO₂and n-type Zn O semiconductors with different weight ratios,a novel dual-layer electrolyte was prepared by one-step dry pressing method.It is found that the cell performance is related to the thickness of the p-and n-type layers.At 550℃,the device using 3CuFeO₂-7Zn O（30 wt.%CuFeO₂,70 wt.%Zn O）electrolyte exhibits an open-circuit voltage（OCV）of 1.06 V and a peak power density（PPD）of 557 m W cm^-2,significantly better than the directly mixed CuFeO₂-Zn O(468 m W cm^-2)and Zn O(300m W cm^-2)electrolytes.The results of energy band structure and rectification characteristics confirm the exsitence of p-n junction.Additionally,the Zn O layer reduces the electronic conductivity,thus avoiding short-circuiting.（2）Schottky junction has been employed to construct LT-SOFC.During the device using CuFeO₂-Zn O dual-layer electrolyte running,a slight of metal was detected without short-circuiting occurrence.In this paper,according to the theory of metal-semiconductor heterojunction,different metal-semiconductor composite electrolytes with low cost were prepared.By comparing the electrochemical test results,316L stainless steel-Ti O₂composites with different weight ratios were selected for further study.At 550℃,the fuel cell with TF3070（30 wt.%Ti O₂,70 wt.%316L stainless steel）electrolyte achieves an OCV of 1.02 V and a PPD of 540 m W cm^-2.Rectification characteristics confirm the existence of metal-semiconductor heterojunction.However,the synergistic effect between the alloy and the semiconductor needs to be further studied.The cheap metal-semiconductor heterocomposite electrolyte has a good market for LT-SOFC.