The significance of converting CO2 into valuable feedstock is highly emphasized with the carbon neutrality vision. Generally, CO and H-2 are usually applied as the protective gases during CO2 electrolysis in nickel based Solid Oxide Electrolysis Cell (SOEC). In this paper, the effects of H-2 and CO as protective gases on the performance of a Ni-YSZ (yttria stabilization zirconia) based SOEC are studied. The electrode processes of the cell are investigated by the electrochemical impedance spectroscopy (EIS) and calculated distribution of relaxation times (DRT) results. The results show that CO makes little difference on the performance of the cell while the cell shows a superior performance with H2 as protective gas, indicating different mechanisms behind. The distinct discrepancies in characteristic frequency ranges of electrode processes with the CO2-CO and CO2-H2 mixtures show that the replacement of CO by H-2 changes the reduction pathway of CO2 from electrochemical reduction to thermochemical reduction, and only steam is electrolyzed. However, the direct injection of steam deteriorates slightly the performance of SOEC. The effect of reverse water gas shift (RWGS) reaction on the electrochemical performance of SOEC is explored and its effect of delaying the concentration polarization and extending the limiting current density is confirmed. Furthermore, the unique pattern of flattened j-V curve at high applied current of CO2 electrolysis is repeatedly emphasized. (c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
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机译:碳中和愿景高度强调了将二氧化碳转化为有价值的原料的重要性。通常,在镍基固体氧化物电解槽(SOEC)中,CO2电解过程中通常使用CO和H-2作为保护气体。本文研究了H-2和CO作为保护气体对Ni-YSZ(氧化钇稳定氧化锆)SOEC性能的影响。通过电化学阻抗谱(EIS)和计算的弛豫时间分布(DRT)结果研究了电池的电极过程。结果表明,CO对电池性能影响不大,而以H2为保护气体,电池性能优越,表明其背后的机理不同。CO2-CO和CO2-H2混合物在电极工艺的特征频率范围上存在明显差异,表明H-2取代CO2使CO2的还原途径由电化学还原转变为热化学还原,仅电解蒸汽。然而,直接注入蒸汽会略微降低SOEC的性能。探究了逆向水气变换(RWGS)反应对SOEC电化学性能的影响,并证实了其延缓浓度极化和延长极限电流密度的作用。此外,还反复强调了在CO2电解的高电流下j-V曲线变平的独特模式。(c) 2022 Hydrogen Energy Publications LLC.,由爱思唯尔有限公司出版。保留所有权利。
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