One of the grand challenges facing humanity today is the development of an alternative energy system that is safe, clean, and sustainable and where combustion of fossil fuels no longer dominates. A distributed renewable electrochemical energy and mobility system (DREEMS) could meet this challenge¹. At the foundation of this new energy system, we have chosen to study a number of electrochemical devices including fuel cells, electrolyzers, and flow batteries. For all these devices electrocatalysis and polymer electrolytes play a critical role in controlling their performance, cost, and durability, and thus their economic viability. In this presentation, I will focus on our work on hydroxide exchange membrane fuel cells (HEMFCs)² which can work with nonprecious metal catalysts³ and inexpensive hydrocarbon polymer membranes⁴. More specifically I will show the roadmap we have developed for HEMFCs to achieve performance parity with proton exchange membrane fuel cells⁵, the progress we have made in developing the most stable membranes and the most active nonprecious metal catalysts⁶. I will also discuss our work on addressing cell/system level issues like reverse current decay and water management^7-9, and why hydrogen oxidation reactions are slower in base than in acid for precious metal catalysts^10-12.

References

(1) S. Gu, B. Xu, Y. Yan. Electrochemical Energy Engineering: A New Frontier of Chemical Engineering Innovation. Annual Review of Chemical and Biomolecular Engineering 2014, 5: 429-454.

(2) S. Gu, R. Cai, T. Luo, Z. Chen, M. Sun, Y. Liu, G. He, Y. Yan. A Soluble and Highly Conductive Ionomer for High-Performance Hydroxide Exchange Membrane Fuel Cells. Angewandte Chemie-International Edition 2009, 48(35): 6499-6502.

(3) S. Gu, W. Sheng, R. Cai, S. M. Alia, S. Song, K. O. Jensen, Y. Yan. An efficient Ag-ionomer interface for hydroxide exchange membrane fuel cells. Chemical Communications 2013, 49(2): 131-133.

(4) S. Gu, J. Wang, R. B. Kaspar, Q. Fang, B. Zhang, E. B. Coughlin, Y. Yan. Permethyl Cobaltocenium (Cp-2*Co+) as an Ultra-Stable Cation for Polymer Hydroxide-Exchange Membranes. Scientific Reports 2015, 5.

(5) B. P. Setzler, Z. Zhuang, J. A. Wittkopf, Y. Yan. Activity targets for nanostructured platinum group-metal-free catalysts in hydroxide exchange membrane fuel cells. Nature Nanotechnology 2016, 11(12): 1020-1025.

(6) Z. Zhuang, S. A. Giles, J. Zheng, G. R. Jenness, S. Caratzoulas, D. G. Vlachos, Y. Yan. Nickel supported on nitrogen-doped carbon nanotubes as hydrogen oxidation reaction catalyst in alkaline electrolyte. Nature Communications 2016, 7.

(7) R. B. Kaspar, Y. Yan. Communication-Patterned Electrodes to Increase Water Back-Diffusion in Hydroxide Exchange Membrane Fuel Cells. Journal of the Electrochemical Society 2016, 163(7): F593-F595.

(8) R. B. Kaspar, J. A. Wittkopf, M. D. Woodroof, M. J. Armstrong, Y. Yan. Reverse-Current Decay in Hydroxide Exchange Membrane Fuel Cells. Journal of the Electrochemical Society 2016, 163(5): F377-F383.

(9) R. B. Kaspar, M. P. Letterio, J. A. Wittkopf, K. Gong, S. Gu, Y. Yan. Manipulating Water in High-Performance Hydroxide Exchange Membrane Fuel Cells through Asymmetric Humidification and Wetproofing. Journal of the Electrochemical Society 2015, 162(6): F483-F488.

(10) W. Sheng, M. Myint, J. G. Chen, Y. Yan. Correlating the hydrogen evolution reaction activity in alkaline electrolytes with the hydrogen binding energy on monometallic surfaces. Energy & Environmental Science 2013, 6(5): 1509-1512.

(11) W. Sheng, Z. Zhuang, M. Gao, J. Zheng, J. G. Chen, Y. Yan. Correlating hydrogen oxidation and evolution activity on platinum at different pH with measured hydrogen binding energy. Nature Communications 2015, 6.

(12) J. Zheng, W. Sheng, Z. Zhuang, B. Xu, Y. Yan. Universal dependence of hydrogen oxidation and evolution reaction activity of platinum-group metals on pH and hydrogen binding energy. Science Advances 2016, 2(3).