Li Ping'an, Zhou Zihan, Qiu Diankai, Peng Linfa
State Key Laboratory of Mechanical System and Vibration, Shanghai Jiao Tong University, Shanghai, 200240, P. R. China.
Shanghai Key Laboratory of Digital Manufacture for Thin-walled Structures, Shanghai Jiao Tong University, Shanghai, 200240, P. R. China.
Adv Sci (Weinh). 2024 Nov;11(43):e2405658. doi: 10.1002/advs.202405658. Epub 2024 Sep 26.
The proton exchange membrane water electrolyzer (PEMWE) is one of the most promising electrochemical energy conversion devices for hydrogen production, while still limited by performance bottlenecks at high current densities, due to the lack of mass transfer insights. To investigate the mechanisms of oxygen transport inside the PEMWE at high current density and its relation to electrolytic performance. Operational in situ x-ray imaging is utilized to simultaneously characterize the bubble behavior and voltage response in a novel designed visual mini-cell, and it is identified that oxygen evolution and transport in the PEMWE follow the process of bubble nucleation, growth, and detachment. Based on the results of mini-cells with three porous transport layers (PTLs) up to 9 A cm operation, it revealed that critical current densities exist for both carbon-based and titanium-based PTLs. Once exceeding the critical current density, the cell voltage can no longer be stabilized and the cell exhibits a significant oxygen overpotential. To illustrate this, the concept of interfacial separation zone (ISZ) is first proposed, which is an effective pathway for bubble growth and separation and the pattern of the ISZ exhibits specific regimes with the critical current density. Ultimately, a new approach for better understanding the mechanisms of oxygen transport is revealed.
质子交换膜水电解槽（PEMWE）是最具前景的用于制氢的电化学能量转换装置之一，但由于缺乏传质方面的认识，在高电流密度下仍受性能瓶颈的限制。为了研究PEMWE在高电流密度下内部氧传输的机制及其与电解性能的关系，利用原位X射线成像操作在一个新设计的可视化微型电解槽中同时表征气泡行为和电压响应，并确定PEMWE中的析氧和氧传输遵循气泡成核、生长和脱离的过程。基于具有三种多孔传输层（PTL）的微型电解槽在高达9 A/cm运行时的结果，发现碳基和钛基PTL均存在临界电流密度。一旦超过临界电流密度，电池电压就无法再稳定，电池会表现出显著的氧过电位。为了说明这一点，首先提出了界面分离区（ISZ）的概念，它是气泡生长和分离的有效途径，并且ISZ的模式在临界电流密度下呈现出特定的状态。最终，揭示了一种更好地理解氧传输机制的新方法。
