(287c) 3D Printed Membraneless Electrolyzers for Hydrogen Production

Hydrogen (H₂) is a promising energy carrier for a clean energy future, but the vast majority of today’s H₂ is produced by CO₂-producing steam methane reforming.  A truly sustainable hydrogen economy will be one in which H₂ is produced using renewable energy. One means of doing this is by using renewable electricity (e.g. from solar or wind) to produce H₂ from the electrolysis of water.[1,2] Unfortunately, the price of H₂ produced by water electrolysis (≈$5 / kg H₂) remains above the U.S. DOE target of $2-4 /kg H₂. In this work, we report on a new cell design for water electrolysis with the goal of closing this price gap by i.) employing a simple, membraneless electrolyzer design and  ii.) exploring the use of 3D printers to manufacture modular electrolyzers in a scalable fashion. Additive manufacturing, aka 3D printing, is especially attractive for this application due to the ability to rapidly prototype, and potentially manufacture, low-temperature electrochemical cells based on low-cost and bio-renewable materials such as polylactic acid.

The membrane is a crucial component of the conventional PEM electrolyzer, providing an ion-conducting pathway between the anode and cathode while separating the H₂ and O₂ product species. However, membranes can be costly, prone to failure, susceptible to cross-over issues, and limit the choice of solution pH.[3,4] In our design, a flowing electrolyte solution passes through two flow-through electrodes, which are positioned to minimize solution resistance and achieve highly efficient separation of the H₂ and O₂ product gases. The results compare well with a recently reported membraneless fuel cells[3] and a microfluidic electrolyzer,[4] but fundamental differences between flow-by and flow-through electrodes make this novel design more scalable and amenable to bulk manufacturing. In addition to standard electroanalytical characterization of the membraneless electrolyzer, we have employed high speed video and integrated sensors to systematically explore the influence of key operating parameters and develop a deeper understanding of the hydrodynamics in this device.

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): 5043–5052.

[3.] Braff, W. A., Bazant, M. Z., and Buie, C. R., Nature Communications 4, (2013): 2346

[4.] H. Hashemi, et al., Energy & Environmental Science (2015), DOI: 10.1039/C5EE00083A.