Modeling Gas Bubbles in Water Electrolyzers across Length Scales

As water electrolyzers scale to larger current densities, reactor designs must be re-evaluated to handle the subsequently high rates of gas bubble formation. Without proper transport, gas bubbles can become entrained on the electrode surface, block active sites, and hamper the flow of water and ions. These events decrease the energy efficiency of the electrolyzer, and over time can even lead to the mechanical failure of components within the device. Modeling the transport behavior of gas bubbles can guide the design of electrodes, porous transport layers, and flow fields. Gas bubble transport is notoriously complicated, however, with physical interactions spanning across several length scales and time scales. This talk explores how we can use multiscale modeling tools to deconvolute this problem and improve our understanding of gas transport in electrochemical systems. At the surface scale, we use molecular dynamics simulations to explore the relationship between nanobubbles, surface defects, and dissolved hydrogen. At the continuum scale, a volume of fluid model can be used to explore the relationship between fluid flow and macroscopic bubble transport. Using 3D printing, we can manufacture optically transparent pores to visualize the flow of bubbles to begin validating these models. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.