Scalable Elastomeric Membranes for Alkaline Water Electrolysis. Author Name: Yu Seung Kim Date: November 13, 2017 Venue: NREL

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1 Scalable Elastomeric Membranes for Alkaline Water Electrolysis Author ame: Yu Seung Kim Date: ovember 13, 2017 Venue: REL

2 HydroGE Kick-Off Meeting Scalable Elastomeric Membranes for Alkaline Water Electrolysis Yu Seung Kim, Los Alamos ational Laboratory Chulsung Bae, Rensselaer Polytechnic Univ. Kathy Ayers, Proton Onsite Project Vision Preparing durable and economically-affordable alkaline hydroxide conducting materials based on quaternaized SEBS and demonstrating the performance and durability in alkaline membranebased water system Project Impact This technology will bring the alkaline membranebased water electrolysis technology to a maturity level at which it can be further developed by industry for commercialization. Award # Year 1 Funding EE000XXXX $278,000 OH OH HydroGE: Advanced Water Splitting Materials 2

3 Innovation and Objectives Project history Los Alamos team (in collaboration with SL and Proton Onsite) demonstrated > 2000 h alkaline electrolyzer durability using polyaromatic electrolytes in In this project, we are aiming to develop economically viable eleastormeric ionomers having at lease equivalent conductivity with much improved mechanical properties. Barriers Alkaline stability hydroxide conductivity Mechanical properties Proposed targets Metric Hydroxide conductivity (ms/cm) % loss conductivity after 300 h, 1 M aoh, 80 C Tensile toughness (Mpa % elongation) State of the Art Proposed < Partnerships Professors Chulsung Bae and Sang Woo Lee (RPI): Polymer Synthesis Dr. Kathy Ayers (Proton Onsite): Electrolyzer testing Drs. Adam Weber and Amhet Kusoglu (LBL): modeling and membrane characterization HydroGE: Advanced Water Splitting Materials 3

4 Polymer Backbone Stability Early Problem of Alkaline Membrane Instability due to polymer backbone degradation O OH *AEM after 0.5 M aoh treatment OH Aryl-ether cleavage reaction* * (Fujimoto et al. J. Memb. Sci. 423, 438 (2012) Tested by Proton Onsite (2013) LAL started to preparing aryl-ether free alkaline membranes (in collaboration with SL and RPI) voltage (V) duration (h) HydroGE: Advanced Water Splitting Materials Quarternized Diels-Alder Polyphenylene Commercial AEM (Tokuyama) Quaternized poly(arylene ether sulfone)

5 Cationic Group Stability Instability of benzyl ammonium cationic group ucleophilic substitution reaction * (Choe et al. Chem. Mater. 26, 5675 (2014) 100 LAL started to preparing alkyl ammonium tethered alkaline membranes Hydroxide conductivity (ms/cm) o C, 4 M aoh Backbone & cationic group stabilized Backbone stabilized Time (h) HydroGE: Advanced Water Splitting Materials 5

6 Backbone and Cationic Group Stabilized AEMs from LAL Team HMTM Series SPG Series AR Series SEBS Series CH 3 H 3C CH 3 CH 3 H 3C CH 3 O O * * F O H 3C CH 3 H 3C CH 3 CH 3 CH 3 Excellent alkaline stability Hexamethyl ammonium functionalized poly(phenylene) AEM (SL) High Designed for enhanced cation stability Strength Improved cation stability Better gas permeability Phenyl guanidinium functionalized AEM (SL & LAL) Introducing stable super base Strength (expected) Improved cation stability Better dimensional stability via lower water uptake Hexamethyl ammonium functionalized poly(biphenylene) AEM (RPI) Introducing flexible alkyl group into the polymer backbone Strength (expected) Improved mechanical properties SEBS based AEM (RPI) Highly conductive & stable polymers Strength High conductivity Good polymer stability Mechanical toughness Down-selected for AMFC project Selected for HydroGE project HydroGE: Advanced Water Splitting Materials 6

7 Technology Innovation: Scalable Synthesis of SEBS Conventional Low level of functionalization & gelation Only allow benzyl ammonium functionalization Toxic and expensive reagents Excellent alkaline stability High Metal catalyzed ot practical due to expensive metal catalysts are used Acid catalyzed (proposed) Friedel-Crafts alkylation HydroGE: Advanced Water Splitting Materials 7

8 Effective Leveraging of the EM Resource odes LAL team have all necessary components to prepare alkaline anion exchange membranes. EM nodes from LBL s modeling and additional characterization techniques for alkaline membranes may help to optimize the membrane properties of alkaline membrane based LTE. LAL team has good collaborative works with LBL researchers from existing fuel cell programs Baseline performance of alkaline membrane based LTE may need to be provided by EM odes. HydroGE: Advanced Water Splitting Materials 8