(68c) Polymer Hydroxide Exchange Membranes for Electrochemical Energy Conversion and Storage

Energy has been central to human civilization. The availability of cheap and abundant fossil energy is primarily responsible for the fastest ever human progress for the past 100+ years. With the depletion of fossil energy, the increase of world population, the improvement of living standard in large population centers, and the concern of the air quality and climate change, one of the grand challenges facing humanity today is the development of an alternative energy system that is clean, safe, and sustainable and where combustion of fossil fuels no longer dominates. Fuel cells, electrolyzers, solar hydrogen, and redox flow batteries when combined could represent such as system.^[1] For our fuel cell efforts, we have been focusing on developing catalyst and membrane materials that will help to solve the cost and durability problems. Our fuel cell work began with the exploration of carbon nanotubes (CNTs) as durable catalyst supports^[12]. We later explored the concept of platinum nanotubes (PtNTs) catalysts that were shown to have significantly improved durability and activity for the oxygen reduction reaction in proton exchange membrane fuel cells (PEMFCs)^[3]. This catalyst platform has the potential to meet the mass and specific activity targets for vehicle applications specified by the US Department of Energy. We have also studied hydrogen generation by photocatalytic water splitting.^[4] In this presentation, I will focus on our recent work on hydroxide exchange membrane (HEMs)^[5]. HEMs, when used in fuel cells (HEMFCs), allow the platinum catalysts to be replaced by non-platinum-group-metals such as nickel and silver while the expensive fluorinated polymer membrane substituted by a hydrocarbon membrane, thus drastically reducing the cost of fuel cells and making them potentially economically viable. HEMs can also be used in electrolyzers and solar hydrogen generators or redox flow batteries for hydrogen generation and large scale solar/wind electricity storage.

References:

1. S. Gu, B. Xu, Y. Yan, 2014. Electrochemical Energy Engineering: A New Frontier of Chemical Engineering Innovation, Annu. Rev. Chem. Biomol. Eng., http://www.annualreviews.org/doi/abs/10.1146/annurev-chembioeng-060713-040114.
2. G. Gu, B.J. Xu, Y.  Yan C. Wang, M. Waje, X. Wang, J. M. Tang, R. C. Haddon, Y. Yan 2004. Proton exchange membrane fuel cells with carbon nanotube based electrodes, Nano Lett. 4:345-348.
3. Z. Chen, W. Li, M. Waje, Y. S. Yan 2007. Supportless Pt and PtPd nanotubes as electrocatalysts for oxygen reduction reaction, Angew. Chem. Int. Ed. 46:4060-4063.
4. H. Luo, T. Takata, Y. Lee, K. Domen, J. Zhao, Y. Yan 2004. Photocatalytic activity enhancing for titanium dioxide by co-doping with bromine and chlorine, Chem. Mater. 16:846-849.
5. S. Gu, R. Cai, T. Luo, Z. Chen, M. Sun, Y. Liu, G. He, Y. Yan 2009. A Soluble and Highly Conductive Ionomer for High Performance Hydroxide Exchange Membrane Fuel Cells, Angew. Chem. Int. Ed., 48: 6499-6502.