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Composite Cathode Based on Redox-Reversible Nb2TiO7 for Direct High-Temperature Steam Electrolysis
Shi-song Li,Ji-gui Cheng*,Xu-cheng Zhang,Yu Wang,Kui Xie*
Author NameAffiliationE-mail
Shi-song Li Department of Energy Materials, School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009, China  
Ji-gui Cheng* Department of Energy Materials, School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009, China jgcheng63@sina.com 
Xu-cheng Zhang Department of Energy Materials, School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009, China  
Yu Wang Department of Energy Materials, School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009, China  
Kui Xie* Department of Energy Materials, School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009, China xiekui@hfut.edu.cn, 
Abstract:
Ni/YSZ fuel electrodes can only operate under strongly reducing conditions for steam electrolysis in an oxide-ion-conducting solid oxide electrolyzer (SOE). In atmosphere with a low content of H2 or without H2, cathodes based on redox-reversible Nb2TiO7 provide a promising alternative. The reversible changes between oxidized Nb2TiO7 and reduced Nb1.33Ti0.67O4 samples are systematically investigated after redox-cycling tests. The conductivities of Nb2TiO7 and reduced Nb1.33Ti0.67O4 are studied as a function of temperature and oxygen partial pressure and correlated with the electrochemical properties of the composite electrodes in a symmetric cell and SOE at 830 oC. Steam electrolysis is then performed using an oxide-ion-conducting SOE based on a Nb1.33Ti0.67O4 composite fuel electrode at 830 oC. The current-voltage and impedance spectroscopy tests demonstrate that the reduction and activation of the fuel electrode is the main process at low voltage; however, the steam electrolysis dominates the entire process at high voltages. The Faradic efficiencies of steam electrolysis reach 98.9% when 3%H2O/Ar/4%H2 is introduced to the fuel electrode and 89% for that with introduction of 3%H2O/Ar.
Key words:  Redox-reversible, Alternative fuel electrode, Solid oxide electrolyzer, Steam electrolysis
FundProject:
氧化还原可逆Nb2TiO7复合阴极电解池高温水蒸气电解研究
李世松,程继贵*,张旭晨,王语,谢奎*
摘要:
系统地研究Nb2TiO7与Nb1.33Ti0.67O4材料相互转变的氧化还原循环可逆性能,同时研究Nb2TiO7和Nb1.33Ti0.67O4样品随温度和氧分压变化的电导率,并与复合电极对称电池和电解池的电化学性能相关联. 在830 oC下,对Nb1.33Ti0.67O4复合电极电解池进行水蒸气的电解研究测试. 电流电压曲线和电解池短期性能测试表明在低电压下主要为电极的还原和活化过程;而在高电压下主要为水蒸气的电解. 当3%H2O/Ar/4%H2气体通入阴极时电解池水蒸气电解的法拉第效率为98.9%;而当通入气体转换为3%H2O/Ar时效率为89%.
关键词:  氧化还原可逆电极,固体氧化物电解池,Nb2TiO7,水蒸气 电解,Nb1.33Ti0.67O4
DOI:10.1063/1674-0068/28/cjcp1412210
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