Jingke Mo, Zhenye Kang, Gaoqiang Yang, Derrick Talley, and Feng-Yuan Zhang^*

Nano HELP : Nanodynamics and High Efficiency Lab for Propulsion & Power

Department of Mechanical, Aerospace and Biomedical Engineering,

UT Space Institute, University of Tennessee, Knoxville

^*fzhang@utk.edu

Abstract

Polymer electrolyte membrane electrolyzer cells (PEMECs) have been considered as one of the most effective and environment-friendly way for energy storage when coupled with renewable energy sources. In PEMECs, water is electrochemically split into oxygen and hydrogen. At the anode side, the circled water flows over the liquid/gas diffusion layer (LGDL) and diffuses to the triple-phase boundaries (TPBs) - the catalyst layers, where it is decomposed into oxygen, electrons, and protons. The proton will transport through the proton exchange membrane (PEM), reach the cathode catalyst layer, and form hydrogen at the cathode side. Due to limitations of the designs of conventional PEMECs and LGDLs, the microspatial and microtemporal scales of the electrochemical reactions, the phenomena of TPB electrochemical reactions has never been explored in operating PEMECs in-situ.

In this research, an innovatively designed transparent PEMEC was developed, and the thin and well-tuned titanium LGDLs with straight-throughout pores were fabricated. A high-speed and micro-scale visualization system (HMVS) was built for in-situ characterizations. The TPB electrochemical reactions only occurred at the edges adjacent to the good conductive materials. Visualization results reveal the real phenomena inside an operating PEMEC, which can not only help maximize the utilization of catalyst, but also help to optimize the fabrication of catalyst layer. The discovery will have a lot application on improving the electrochemical devices.