Muhammad Arif(PL) David L. Jacobson (PL) Charles F. Majkrzak(MSEL) Terrence J. Udovic (MSEL) Neutron Metrology for Fuel-Cell Technology

Fuel Cell Development - A National Priority “ Our third goal is to promote energy independence for our country, ….In this century, the greatest progress will come about through..technology and innovation. A single chemical reaction between hydrogen and oxygen generates energy, which can be used to power a car -- producing only water, not exhaust fumes. With a new national commitment, our scientists and engineers will overcome obstacles to taking these cars from laboratory to showroom, so that the first car driven by a child born today could be powered by hydrogen, and pollution-free.” President Bush, State of the Union address, January 22, “Hydrogen fuel cells present one of the most promising emerging technologies in the innovation age. … Many challenges remain in the widespread adoption of fuel cells, both technological and infrastructure related... We can tailor policies and programs to best foster the environment for innovation and commercialization and help charter a cleaner, safer and more prosperous future for all.” Donald L. Evans, Secretary of Commerce, January, 2003

PEM Fuel Cell Basics Output 0.6 V V Good proton conduction Water balance MEA stability Temp. 60 ºC – 85 ºC

Measurement Challenges Micro-scale, non-destructive visualization and mapping of spatial and temporal water distribution inside fuel cells Nano-scale imaging of polymer morphology, proton diffusion, evolution of water domains and depth profile of H 2 O/H 2 across the membrane electrode assembly Accurate quantification of membrane and flow channel H 2 O/H 2 transport dynamics Molecular-scale knowledge of the location, interactions and transport of hydrogen (and water) in fuel cell materials

Comparison of the relative size of the x-ray and thermal neutron scattering cross section  for various elements. x-ray cross section HDCOAlSiFe neutron cross section Sample t N – numerical density of sample atoms per cm 3 I 0 - incident neutrons per second per cm 2  - neutron cross section in ~ cm 2 t - sample thickness Neutrons are Perfect Probes Sensitivity, Penetration, and Dynamic Range

Water management Membrane Morphology New materials Molecular-scale neutron scattering measurements to characterize structure, bonding, and dynamics in fuel cell materials. Neutron reflectometry and small angle scattering to study nano-scale membrane morphology and defects. Neutron transmission and phase imaging methods to visualize and quantify micro-scale water transport in near real time. Research Approach Develop New Neutron Tools / Metrologies

Imaging Test Station Variable beam diameter Variable resolution Intense neutron beam Single or multi-stack cell

Neutron Imaging Setup Picture of the detector and sample holder assembly Radiograph (absorption/scattering) Phase Contrast Imaging Pinhole collimator Neutron beam Fuel cell Light tight box Mirror Lens CCD chip neutron to light converter Computer

Neutron Radiograph and Phase Images RadiographPhase Image A B Phase (rad) Distance (mm) AB It is possible to construct a 3-D phase profile of the object from a 2-D phase image. The neutron-sample interaction is complex when different elements are present and advanced methods for phase retrieval must be developed for accurate image interpretation.

Water Movement in Fuel Cells Low High Water migration Accumulated water The images represent sub-millimeter spatial resolution and a two-second temporal resolution.

Fast, High-Resolution Imaging is the Primary Key Glass Matrix 7  m - charge + charge Amplified event Metal anode detector surface Spatial resolution < 5 µm Temporal resolution < 10 msec Spatial > 200 µm Temporal > 40 msec Requirements / Goals

Coded Aperture For Fast, High-Resolution Imaging Crab Nebula Coded aperture Low Energy Gamma- Ray Imager (LEGRI) Coded aperture enhances intensity without sacrificing resolution. The image contains both phase and intensity modulation information and it is inherently three-dimensional. Applying this technique to neutrons poses serious technical and theoretical challenges. Real time 3-D imaging of membrane would be possible! e e e e H H + + H H + + e e - - e e - -

Neutron Metrology at Smaller Length Scales is Needed It is crucial to correlate micro-scale water behavior with the nanoscale membrane morphology and water/hydrogen distribution. -essential for understanding critical membrane swelling and delamination Rational design of next-generation fuel-cell materials requires a molecular-scale understanding of membrane structures, water/hydrogen-membrane interactions, and protonic-conduction mechanisms. -essential for understanding and tailoring performance, durability, and cyclability Micro-scale water/hydrogen transport results from both nanoscale and molecular-scale diffusion processes.

Nanoscale Imaging with Neutron Reflectometry Neutron Reflectometry is key to nanoscale imaging of water and membrane structure

Nanoscale Imaging with Neutron Reflectometry Water Fraction Scattering Length Density Depth ProfileMembrane Water Image Water Fraction Depth (nm) 20 In situ environments are crucial

Nanoscale Imaging with Small-Angle Neutron Scattering Probing Nanostructure in Fuel-Cell Membranes

Molecular-Scale Metrology for Next-Generation Materials The future of fuel-cell technology also relies on the development and tailoring of new materials. Lower-temperature oxide-type protonic conductors (e.g., rare-earth-doped perovskites) Inorganic solid acids Higher-temperature PEM’s (e.g., polymer blends and composites) We must probe hydrogen on a molecular scale. State-of-the-art neutron scattering methods are again essential, along with theoretical approaches. In situ environments are crucial

Molecular-Scale Characterization with Neutrons MHXO 4 Inorganic Solid Acids M=Rb, Cs X=S, Se, etc. Hydrogen bonds Proton Transfer Probing Molecular-scale Structure, Bonding, and Diffusion in Next-Generation Membrane Materials 2-Fold Rotation 3-Fold Rotation

Depth (nm) Water Fraction NanoscaleMolecular scale Microscale Probing the Entire Range of Length Scales

Deliverables Visual and quantitative characterization of H 2 O/H 2 flow dynamics in operating fuel cells using non-destructive high- resolution neutron imaging Nanoscale mapping of hydrogen and water diffusion, and embedded inhomogeneities in fuel cell membranes and interfaces Combined molecular-scale neutron metrology and first- principles calculations for understanding and tailoring new fuel-cell materials State-of-the-art neutron imaging tools with unparalleled spatial and temporal resolution

Guide efficient and robust design of fuel-cell systems Promotes rational design over trial-and-error approach Reduction in development time NIST-led metrology innovation assures fair access to the technology Support future industry-wide standards For fuel-cell performance and manufacture US competitiveness and security Greater independence from foreign oil New in situ imaging metrology and scattering techniques Contributes to many other programs of NIST and its customers Impacts

Interactions MIT Caltech Los Alamos Varian Nova Scientific Ballard PlugPower Dupont UTC Nuvera General Motors Ford Daimler Chrysler BMW “ There is a need for a public-private manufacturing technology partnership...to be government led...such as [by] the U.S. Department of Commerce…” Hydrogen Energy Roadmap, Washington, DC, April 2002

Industry Response “I wish it [neutron imaging] was ready now” “I would give [the impact importance of fuel cell research] a 5/5 if there were a more focused program with NIST” “[It has] very high potential to help industry with the water management problem in fuel cells …. I hope that is the first company to benefit from this project” “ It is a good idea for industry and national labs [NIST] to collaborate [on fuel cell research]… this gives access to tools and instruments that we [industry] need to have…” NIST Industrial Liaison Office survey of General Motors Ford PlugPower Ballard

Managing Our Resources New FTEs Three Post Doctoral Fellows Graduate Students Leveraged Alliances Personnel

Budget/Personnel Detector Development Scientist (FTE, PL, new hire): will work with industry in the development of high-resolution two-dimensional neutron detectors, including adaptation of optical and x-ray imaging devices for use with neutrons Imaging Scientist (FTE, PL, new hire): will lead development of coded aperture techniques, phase contrast imaging techniques, and development of methods and standards for quantitative elemental density measurements Fuel-Cell Materials Scientist (FTE, MSEL, new hire): will lead collaborative efforts in selecting, tailoring, and characterizing fuel-cell component materials, including new protonic conductors Postdoctoral Researcher (PL, new hire): will develop instrument control and image reconstruction algorithms. Will develop transparent user interface for instrument control and display for external users from industry and other scientific fields. Postdoctoral Researcher (MSEL, new hire): will support development and application of improved experimental neutron scattering methods. Postdoctoral Researcher (MSEL, new hire): will support theory and modeling of fuel-cell materials and nanoscale processes.

Proposed research and expected outcome is strongly consistent with NIST mission to help industry with generic metrology Hydrogen/fuel-cell roadmap points to metrology and standards as central issues Strong and broad demand for NIST to help NIST can create innovative neutron metrologies to address challenges that must be overcome for fuel cells to be commercially viable Cohesive cross-disciplinary research infrastructure to encompass nano- to micro-scale measurements Only U.S. research facility with the capabilities to achieve the goals of this initiative Why NIST?

Conclusions NIST makes unique and timely contributions to needed metrology and research for fuel-cell development. - creates team for the future NIST has a “window of opportunity” to impact fuel-cell technology. - a major national priority NIST establishes ties with key players from industry, government, and universities. - facilitates future NIST role

`` If this works [fuel cells] this is the holy grail, this is the breakthrough. We've done enough work, we think there are risks, and the payoff is not just for the automotive OEM's (original equipment manufacturers), it's the whole economy.'' Rick Wagoner, GM president and CEO, January 14, 2002.

Addendum

Milestones Recruit key staff members Design high-intensity imaging station / Study single-stack fuel cell Design new sample-environment systems for scattering and imaging Complete first measurements of PEM fuel cells and new protonic- conducting oxides Establish NIST/industry/university consortium FY 2004 FY Provide key results on morphology, molecular clustering, and transport to allow improvements in fuel-cell performance Study effect of catalyst dopants on nanoscale behavior of solid-oxide fuel cells Develop neutron reflectometry as a reference method for nanoscale interfacial metrology of fuel cells Measure PEM delamination characteristics and provide measurement data to optimize flow channel design Measure and model compositional effects on performance and cyclability to guide choice of materials for next-generation fuel cells Establish 3-D phase imaging with 5  m resolution Measure water/vapor transport in fuel cells in near real time and establish model parameters Transfer technology to Industry and to other NIST programs FY

Budget DivisionsCategoryFY04FY05FY06FY07FY08 846STRS$550K$600K$650K$675K$700K IE$250K$200K$150K$125K$100K 856STRS$550K $600K IE$50K$0K TotalSTRS+IE$1400K Invested Equipment Purchases PL: The equipment budget is substantial because (i) the rapid technological development of imaging devices implies rapid obsolescence, and (ii) radiation damage shortens the useful life of all these devices. In addition there are substantial costs in neutron beam line development and imaging instrument construction. MSEL: The equipment budget covers the costs of developing custom environmental equipment, samples, and sample cells for in situ neutron scattering measurements.