(519f) Water Electrolysis without Membranes: Opportunities and Limitations

Hydrogen production from water electrolysis is a highly attractive approach to generating an energy-dense fuel that can be stored for long periods of time. This interconversion between hydrogen and electricity is especially attractive in a sustainable energy future when large quantities of low cost electricity are expected to be available. However, it is essential that the capital costs (Capex) of electrolyzer systems be significantly lowered if hydrogen produced from water electrolysis is going to compete with hydrogen produced from steam methane reforming. Achieving this goal will require innovation in the design and manufacturing of electrocatalysts, electrolyzers, and electrolysis systems. Our group is particularly interested in exploring membraneless electrolyzers as alternative device designs to enable new functionalities and lower the levelized cost of hydrogen.^[1-3] These electrolyzers have the potential to have lower capital costs due to reduced number of parts, but also face challenges in achieving high product purity due to hydrogen and oxygen cross-over between electrodes. Here, I will describe the basic operating principles of membraneless water electrolyzers and discuss design rules that dictate the relationship between device geometry, operating conditions, and performance metrics like efficiency and product purity. Another potential advantage of membraneless electrolyzers is the ability to operate in electrolytes that would normally lead to degradation and/or fouling of membranes in the presence of impurities. This advantage motivates our efforts to develop impurity-tolerant electrocatalysts for which ultrathin encapsulation layers allow for selective transport of protons and water while blocking impurities from reaching the electrocatalytically active buried interface.^[4]

[1] D.V. Esposito, “Membraneless Electrolyzers for Low-Cost Hydrogen Production in a Renewable Energy Future”. Joule, 1, 1-8, 2017.

[2] O’Neil G D, et al. 2016 Hydrogen Production with a Simple and Scalable Membraneless Electrolyzer J. Electrochem. Soc. 163 F3012–9

[3] J.T. Davis, et al., “Floating Membraneless PV-Electrolyzer Based on Buoyancy-Driven Product Separation”, International Journal of Hydrogen Energy, vol. 43 (3), pp 1224–1238, 2018.

[4] N. Y. Labrador, E. L. Songcuan, C. De Silva, Han Chen, Sophia Kurdziel, Ranjith K. Ramachandran, Christophe Detavernier, D.V. Esposito, “Hydrogen Evolution at the Buried Interface between Pt Thin Films and Silicon Oxide Nanomembranes”. ACS Catalysis, vol. 8, pp 1767–1778, 2018.