物理化学学报 >> 2019, Vol. 35 >> Issue (3): 284-291.doi: 10.3866/PKU.WHXB201804171

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氧分压对固体氧化物电解池性能的影响

侯权1,3,关成志1,2,3,肖国萍1,2,王建强1,2,*(),朱志远1,2   

  1. 1 中国科学院上海应用物理研究所熔盐化学与工程技术部，上海 201800
    2 中国科学院微观界面物理与探测重点实验室，上海 201800
    3 中国科学院大学，北京 100049
  • 收稿日期:2018-03-21 发布日期:2018-08-28
  • 通讯作者: 王建强 E-mail:wangjianqiang@sinap.ac.cn
  • 基金资助:
    中国科学院战略性先导科技专项(XDA02040600)

Effect of Oxygen Partial Pressure on Solid Oxide Electrolysis Cells

Quan HOU1,3,Chengzhi GUAN1,2,3,Guoping XIAO1,2,Jian-Qiang WANG1,2,*(),Zhiyuan ZHU1,2   

  1. 1 Department of Molten Salt Chemistry and Engineering, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, P. R. China
    2 Key Laboratory of Interfacial Physics and Technology, Chinese Academy of Sciences, Shanghai 201800, P. R. China
    3 University of Chinese Academy of Sciences, Beijing 100049, P. R. China
  • Received:2018-03-21 Published:2018-08-28
  • Contact: Jian-Qiang WANG E-mail:wangjianqiang@sinap.ac.cn
  • Supported by:
    the "Strategic Priority Research Program" of the Chinese Academy of Sciences(XDA02040600)

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摘要：

基于固体氧化物电解池的高温电解水蒸气是一种可以在低碳排放条件下实现大规模氢气制备的技术。固体氧化物电解池的工作条件，尤其是所通入的气体组成和压力对其性能有很大的影响。本文基于计算流体力学软件建立了电解池理论模型来研究固体氧化物电解池的氧电极上通入不同氧分压的吹扫气对电解池反应特性的影响，文中所研究的氧分压范围为1.01 × 103–1.0 × 105 Pa。结果表明，可逆的开路电压随着氧分压的提高而增大，然而由活化极化、欧姆极化和浓差极化共同作用导致的极化电压随着氧分压增大而降低。在低电流密度时氧分压越小固体氧化物电解池性能越好，而在高电流密度时氧分压越大固体氧化物电解池性能越好。因此在低电流密度时采用低氧分压吹扫气有利于降低电解过程的耗电量，在高电流密度时采用氧气作为吹扫气有利于减少电解水的电能消耗并能够得到纯氧作为副产物以提高经济价值。

关键词: 固体氧化物电解池, 界面, 氧分压, 理论模型, 计算流体动力学模拟

Abstract:

High-temperature (700–900 ℃) steam electrolysis based on solid oxide electrolysis cells (SOECs) is valuable as an efficient and clean path for large-scale hydrogen production with nearly zero carbon emissions, compared with the traditional paths of steam methane reforming or coal gasification. The operation parameters, in particular the feeding gas composition and pressure, significantly affect the performance of the electrolysis cell. In this study, a computational fluid dynamics model of an SOEC is built to predict the electrochemical performance of the cell with different sweep gases on the oxygen electrode. Sweep gases with different oxygen partial pressures between 1.01 × 103 and 1.0 × 105 Pa are fed to the oxygen electrode of the cell, and the influence of the oxygen partial pressure on the chemical equilibrium and kinetic reactions of the SOECs is analyzed. It is shown that the rate of increase of the reversible potential is inversely proportional to the oxygen partial pressure. Regarding the overpotentials caused by the ohmic, activation, and concentration polarization, the results vary with the reversible potential. The Ohmic overpotential is constant under different operating conditions. The activation and concentration overpotentials at the hydrogen electrode are also steady over the entire oxygen partial pressure range. The oxygen partial pressure has the largest effect on the activation and concentration overpotentials on the oxygen electrode side, both of which decrease sharply with increasing oxygen partial pressure. Owing to the combined effects of the reversible potential and polarization overpotentials, the total electrolysis voltage is nonlinear. At low current density, the electrolysis cell shows better performance at low oxygen partial pressure, whereas the performance improves with increasing oxygen partial pressure at high current density. Thus, at low current density, the best sweep gas should be an oxygen-deficient gas such as nitrogen, CO2, or steam. Steam is the most promising because it is easy to separate the steam from the by-product oxygen in the tail gas, provided that the oxygen electrode is humidity-tolerant. However, at high current density, it is best to use pure oxygen as the sweep gas to reduce the electric energy consumption in the steam electrolysis process. The effects of the oxygen partial pressure on the power density and coefficient of performance of the SOEC are also discussed. At low current density, the electrical power demand is constant, and the efficiency decreases with growing oxygen partial pressure, whereas at high current density, the electrical power demand drops, and the efficiency increases.

Key words: Solid oxide electrolysis cell, Interface, Oxygen partial pressure, Theoretical model, Computational fluid dynamics