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Framework for evaluating the performance limits of membraneless electrolyzers
Energy & Environmental Science ( IF 32.4 ) Pub Date : 2020-09-15 , DOI: 10.1039/d0ee02268c Xueqi Pang 1, 2, 3, 4, 5 , Jonathan T. Davis 1, 2, 3, 4, 5 , Albert D. Harvey 6, 7, 8 , Daniel V. Esposito 1, 2, 3, 4, 5
Energy & Environmental Science ( IF 32.4 ) Pub Date : 2020-09-15 , DOI: 10.1039/d0ee02268c Xueqi Pang 1, 2, 3, 4, 5 , Jonathan T. Davis 1, 2, 3, 4, 5 , Albert D. Harvey 6, 7, 8 , Daniel V. Esposito 1, 2, 3, 4, 5
Affiliation
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Emerging membraneless electrolyzers offer an attractive approach to lowering the cost of hydrogen (H2) production from water electrolysis thanks to potential advantages in durability and manufacturability that are made possible by elimination of membranes or diaphragms from the device architecture. However, a fair comparison of the performance limits of membraneless electrolyzers to conventional electrolyzers is hindered by the early stage of research and absence of established design rules for the former. This task is made all the more difficult by the need to quantitatively describe multiphase flow between the electrodes in membraneless electrolyzers, which can have a huge impact on gas product purity. Using a parallel plate membraneless electrolyzer (PPME) as a model system, this study takes a combined experimental and modeling approach to explore its performance limits and quantitatively describe the trade-offs between efficiency, current density, electrode size, and product purity. Central to this work is the use of in situ high-speed videography (HSV) to monitor the width of H2 bubble plumes produced downstream of parallel plate electrodes as a function of current density, electrode separation distance, and the Reynolds number (Re) associated with flowing 0.5 M H2SO4 electrolyte. These measurements reveal that the HSV-derived dimensionless bubble plume width serves as an excellent descriptor for correlating the aforementioned operating conditions with H2 crossover rates. These empirical relationships, combined with electrochemical engineering design principles, provide a valuable framework for exploring performance limits and guiding the design of optimized membraneless electrolyzers. Our analysis shows that the efficiencies and current densities of optimized PPMEs constrained to H2 crossover rates of 1% can exceed those of conventional alkaline electrolyzers but are lower than the efficiencies and current densities achieved by zero-gap polymer electrolyte membrane (PEM) electrolyzers.
中文翻译：
评估无膜电解槽性能极限的框架
新兴的无膜电解槽为降低氢气（H 2）的水电解生产，这归功于其耐用性和可制造性方面的潜在优势，而这种优势可通过消除设备结构中的隔膜或隔膜来实现。然而，由于研究的早期阶段以及缺乏针对前者的既定设计规则，妨碍了将无膜电解器与常规电解器的性能极限进行合理比较。由于需要定量描述无膜电解槽中电极之间的多相流，这使这项工作变得更加困难，这可能会对气体产物的纯度产生巨大影响。本研究使用平行板无膜电解器（PPME）作为模型系统，采用实验和建模相结合的方法来探索其性能极限并定量描述效率之间的权衡，电流密度，电极尺寸和产品纯度。这项工作的核心是使用原位高速摄像（HSV），以监测平行板电极下游产生的H 2气泡羽流的宽度，该宽度是电流密度，电极分离距离和与流动0.5 MH 2 SO 4相关的雷诺数（Re）的函数电解质。这些测量结果表明，HSV衍生的无量纲气泡羽宽是将上述操作条件与H 2相关联的极佳描述子交叉率。这些经验关系与电化学工程设计原理相结合，为探索性能极限和指导优化的无膜电解槽的设计提供了宝贵的框架。我们的分析表明，约束为1％的H 2穿越率的优化PPME的效率和电流密度可以超过传统的碱性电解槽，但低于零间隙聚合物电解质膜（PEM）电解槽实现的效率和电流密度。
更新日期：2020-10-14
中文翻译：
评估无膜电解槽性能极限的框架
新兴的无膜电解槽为降低氢气（H 2）的水电解生产，这归功于其耐用性和可制造性方面的潜在优势，而这种优势可通过消除设备结构中的隔膜或隔膜来实现。然而，由于研究的早期阶段以及缺乏针对前者的既定设计规则，妨碍了将无膜电解器与常规电解器的性能极限进行合理比较。由于需要定量描述无膜电解槽中电极之间的多相流，这使这项工作变得更加困难，这可能会对气体产物的纯度产生巨大影响。本研究使用平行板无膜电解器（PPME）作为模型系统，采用实验和建模相结合的方法来探索其性能极限并定量描述效率之间的权衡，电流密度，电极尺寸和产品纯度。这项工作的核心是使用原位高速摄像（HSV），以监测平行板电极下游产生的H 2气泡羽流的宽度，该宽度是电流密度，电极分离距离和与流动0.5 MH 2 SO 4相关的雷诺数（Re）的函数电解质。这些测量结果表明，HSV衍生的无量纲气泡羽宽是将上述操作条件与H 2相关联的极佳描述子交叉率。这些经验关系与电化学工程设计原理相结合，为探索性能极限和指导优化的无膜电解槽的设计提供了宝贵的框架。我们的分析表明，约束为1％的H 2穿越率的优化PPME的效率和电流密度可以超过传统的碱性电解槽，但低于零间隙聚合物电解质膜（PEM）电解槽实现的效率和电流密度。
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