Design of a Light-Weight Low-Volume High Oxygen Storage Density Material by Nicholas Robert Schwartz Bachelor of Science in Chemical Engineering University of Wisconsin, Madison 2009 A thesis submitted to the Department of Chemical Engineering at Florida Institute of Technology in partial fulfillment of the requirements for the degree of Master of Science in Chemical Engineering Melbourne, FL May, 2014 We, the undersigned committee, hereby approve the attached thesis, “Design of a Light-Weight Low-Volume High Oxygen Storage Density Material” by Nicholas Robert Schwartz _________________________ _________________________ Paul Jennings, Ph.D. Justin Hill, Ph.D. Associate Professor Adjunct Professor Department of Chemical Engineering Department of Chemical Engineering Committee Chair Thesis Advisor _________________________ _________________________ Joel Olson, Ph.D. James Brenner, Ph.D. Associate Professor Assistant Professor Department of Chemistry Department of Chemical Engineering _________________________ Manolis Tomadakis, Ph.D. Professor and Department Head Department of Chemical Engineering ABSTRACT Title: Design of Light-weight Low-volume High Oxygen Storage Density Material Author: Nicholas Robert Schwartz Advisor: Dr. Justin J. Hill A compact, lightweight, dense and safe method for storing and supplying oxygen remains a large hurdle for closed-circuit self-contained breathing apparatus (SCBA) and respiratory protective equipment. No filter that can protect against airborne chemical, biological, radiological, and nuclear (CBRN) contaminants exists, which presents the need for an isolated oxygen source. Heavy and high maintenance oxygen cylinders are typically used. The most important criteria for a smart and effective CBRN protection device are safety, weight, size, and cost, level of maintenance, ease-of-use and reliability. This study focused on nanomaterials for high capacity gas storage. Nanocapillary arrays composed of anodic aluminum oxide (AAO) were evaluated as high pressure storage materials. Carbon nanotubes (CNT) were integrated in the pores to increase pressure tolerance and act as an electrical conductor. A membrane electrode assembly (MEA) was used to seal the nanocapillaries and to allow for electrochemical gas compression within the system. The volumetric and gravimetric storage capacity of the nanomaterials was calculated to be 1,139 g/L and 0.616 g/g, respectively. Micropore blowout pressure experiments estimated a 500 nm membrane cap in the AAO could seal against 45,000 psi. Nanocapillaries were integrated with membrane material with penetration depths between 1−400 µm within 100 nm wide nanocapillaries. Electrochemical oxygen pumping and compression with open and closed pore nanocapillary-MEAs was performed. iii TABLE OF CONTENTS Abstract ................................................................................................................... iii Table of Contents ................................................................................................... iv Table of Figures ...................................................................................................... vi List of Tables ........................................................................................................... x List of Acronyms .................................................................................................... xi List of Symbols ...................................................................................................... xii Acknowledgements ............................................................................................... xiii Chapter 1: Introduction ......................................................................................... 1 High-Density Gas Storage in Nanocapillary Arrays ............................................ 3 Pressure Seal and Electrochemical Pumping ....................................................... 7 Research Objectives ........................................................................................... 10 Chapter 2: Previous Research ............................................................................. 12 Gas Storage in Capillary Arrays ........................................................................ 12 Fabrication of Nanocapillary Arrays .................................................................. 13 Templated Growth of CNTs within Nanocapillaries ......................................... 14 Integration of Polymer Materials in AAO Templates ........................................ 16 Hydrogen and Oxygen Production with Water Electrolysis .............................. 18 Chapter 3: Methods & Equipment ...................................................................... 21 Fabrication of Nanocapillary Arrays .................................................................. 21 CVD Growth of CNTs within High-Aspect-Ratio Nanocapillaries .................. 24 Evaluation of Oxygen-Storage Density Potential .............................................. 26 Investigation of Pressure Capping and Electrochemical Compression .............. 29 Demonstration of Fabricated Nanocapillary-MEA ............................................ 33 Demonstration of Closed-pore Nanocapillary-MEA ......................................... 37 Analysis of Nanocapillary-MEA and Electrochemical Performance ................ 39 Chapter 4: Development of the High Capacity Gas Storage Material ............. 41 Fabrication of Deep Pore Nanocapillary Arrays ................................................ 41 iv Integration of CNTs within Nanocapillaries by CVD Growth .......................... 43 Evaluation of Oxygen Storage Capacity ............................................................ 45 Development of the High Storage Density Nanomaterials ................................ 48 Chapter 5: Material Selection and Investigation of Nanocapillary Sealing .... 49 Membrane Material Selection ............................................................................ 49 Material Properties ...................................................................................... 50 Micropore Capping and Pressurization .............................................................. 52 Integrating Membrane Material within Nanocapillaries .................................... 55 Integrating Nafion Using Surfactants .......................................................... 55 Filling After Drying AAO ............................................................................. 57 Chapter 6: Development and Demonstration of the Nanocapillary-MEA ...... 61 MEA Fabrication ................................................................................................ 61 Assembly of the nano-MEA .......................................................................... 63 Demonstration of Electrochemical Oxygen Pumping ....................................... 65 Baseline Oxygen Generation Performance .................................................. 65 Performance of Freestanding Characteristic MEA ..................................... 66 Performance of Nanocapillary-Supported MEA .......................................... 69 Overall Device Performance ....................................................................... 70 Demonstration of Closed-pore Nanocapillary-MEA ................................... 74 Alternative Fabrication Method for Nano-MEA .......................................... 80 Chapter 7: Conclusions and Recommendations ................................................ 84 Conclusions ........................................................................................................ 84 Recommendations .............................................................................................. 86 References .............................................................................................................. 89 v TABLE OF FIGURES Figure 1. Schematic of an array of nanocapillary pores within the AAO (a) and a top-down view of a single coaxial AAO-CNT pore showing tunable dimensions ................................................................................................. 3 Figure 2. Process steps for integrating AAO/CNT nanocapillary array with membrane and electrode material .............................................................. 5 Figure 3. Calculated Vc and Gc as a function of AAO nanocapillary diameter (a) and CNT thickness (b) ............................................................................... 6 Figure 4. Oxygen generation by water electrolysis with proton exchange membrane configured in a membrane electrode assembly.......................................... 8 Figure 5. Oxygen compression and generating system integrated with AAO nanocapillaries ........................................................................................... 9 Figure 6. A top-down SEM micrograph view of an AAO template prepared on an aluminum substrate. ................................................................................. 13 Figure 7. Directed tip-growth of CNTs within a nanocapillary array following electrodeposition of a catalyst nano-droplet for CNT growth. ................ 15 Figure 8. FESEM images of CNTs in the AAO, wide view (a), magnification of CNTs (b). ................................................................................................. 16 Figure 9. Chronoamperometric response of successful AAO formation by hard anodization.48 ..........................................................................................