Direct Visualization of Ultra-Fast and Micro-Scale Bubble Evolutions and Electrochemical Reactions in Proton Exchange Membrane Electrolyzer Cells

The electrochemical reactions and two-phase flow that occur in energy devices could be a very important part in promoting energy efficiency of both engineering and sciences. The electrochemical reactions only occur at a micro scale at the center part of the electrochemical devices like fuel cells and electrolyzers. The objective of this research is to visualize the bubble generation and growth process inside a proton exchange membrane electrolyzer cell (PEMEC) by taking advantage of the thin/well tunable liquid gas diffusion layer (LGDL) and high-speed visualization system. The effects of temperature, current density, and flow rate on bubble dynamics in pore scale and multiphase flow in channel scale, including bubble nucleation, growth, and detachment, are investigated. The reaction sites and rapid bubble evolution phenomena are captured under various operating conditions. The number of reaction sites and bubble growth rates increases with the operating current density and temperature, while the flow rate in the channel has limited effects. The gas bubbles are observed to emerge at the edge of the LGDL pores and gradually detach from the reaction sites. This work will provide a pathway to further investigate the electrochemical reaction in energy devices.