Abstract
A sustainable and robust electrochemical energy storage and/or a hybrid system to accommodate daily, even hourly changes of renewable resources becomes more critical. An advanced polymer electrolyte membrane water electrolyzer (PEMWE) has been shown to be effective energy storage medium by producing hydrogen/oxygen from water with electricity from renewable sources. When the renewable resources are available, hydrogen will be produced and stored, such that it can later provide a constant power supply with a PEM fuel cell, which is a reverse device of the electrolyzer. This entire portfolio will make renewable and hybrid energy systems effective to provide reliable and multiscale energy whenever needed.
In proton exchange membrane water electrolyzers (PEMWEs), water is electrochemically splitting into oxygen and hydrogen. The oxygen generated at the anode side and the circled water flowing over the liquid/gas diffusion layer yield two-phase transport conditions in micro-channels and pores of LGDL, which significantly impact the performance. Due to limitations of the design of conventional PEMWEs and LGDLs, the in-situ phenomena of two-phase flow has few been explored in operating PEMWEs. In this research, an innovative design of a transparent PEMWE is developed coupled with the thin and well-tuned titanium LGDLs with straight pores. The high-speed and micro-scale visualization system (HMVS), and electrochemical impedance spectroscopy will be used for in-situ characterizations. Visualization results are used for better understanding the behavior of two-phase flow and its effects on the PEMWE performance. Patterns of gas-bubble formation, evolution, departure and transport are identified. The effects of property of materials, including LGDL pore sizes, channel dimensions, are also investigated.