(405e) Membraneless Electrolyzers for Water Electrolysis

Hydrogen (H₂) is a carbon- free energy carrier with applications in the transportation, electricity, and industrial sectors. The vast majority of todayâ??s H₂ is produced by steam methane reforming, but the production of H₂ from water electrolysis offers a carbon-free route when the electricity is supplied from solar or wind.[1,2] Unfortunately, the price of H₂ produced by water electrolysis (â??$5 / kg H₂) remains above the U.S. DOE target of $2-4 /kg H₂. In this work, we explore simple and scalable membraneless electrolyzers based on angled mesh flow-through electrodes as a means of decreasing the electrolyzer capital costs and thereby bring down the price of producing H₂ from water electrolysis. The electrolyzer capital cost is especially important in instances of low capacity factor and time of use pricing, which are expected to become more prevalent as variable solar and wind generators capture a larger share of the electricity market.

Conventional polymer electrolyte membrane (PEM) electrolyzers rely on membranes to conduct H⁺ ions between electrodes while separating the H₂ and O₂ product species, but these membranes can be costly, prone to failure, limit the choice of solution pH, and require a fairly complex MEA-based architecture.[3,4] Recently, we have demonstrated 3D printed membraneless electrolyzers based on flowing electrolyte through two angled mesh flow-through electrodes, which results in efficient separation of the H₂ and O₂ product gases with minimal product crossover.[3] Ongoing research builds off of this initial study by using in situ high speed video analysis to quantitatively measure current density distributions along angled mesh electrodes under various operating conditions. Experimental observations are compared with modeled current density distributions, providing a useful framework for further optimizing device performance and better understanding the hydrodynamics associated with gas-evolving flow-through electrodes.

References

[1.] B. Kroposki, et al., National Renewable Energy Laboratory - Technical report (2006).

[2.] Millet, P., et al., International Journal of Hydrogen Energy 35, (2010): 5043â??5052.

[3.] G.D. Oâ??Neil, C. Christian, D. Brown, J.T. Davis, D.E. Brown, D.V. Esposito, J. Electrochemical Society, 163, (2016): (In Press).