F. Fuel Cell Electrochemistry
1. Analysis
Description: Basic research, applicable to many types of fuel cells.
a) Electrocatalysis
Description: Study the microstructure and reactivity of the electrocatalyst/electrolyte interface at the anode and cathode of membrane-electrode assemblies.
i. Non-linear optical techniques
Description: Vibrationally-resolved sum-frequency generation
ii. Spectroscopic in-situ probes
iii. Molecular study of reaction intermediates on catalytic surfaces.
iv. Transient femtosecond infrared spectroscopy
Description: Identify transient chemical species on different catalytic surfaces to help identify efficient reaction paths. v. Atomistic modeling of reaction pathways
b) Sorption and transport models
Description: In membranes, models are needed for atomic-level processes (e.g., the coupled motions of polymer chains, water, and protons in polymer electrolytes), proton diffusion and transport in pores, and the relationship between macro-scale conductivity and the structure of pore networks. This helps understand performance factors and durability factors (e.g., critical membrane swelling and delamination).
i. Neutron reflectometry
ii. Small-angle scattering
c) Water distribution mapping
Description: Accurate quantification of membrane and flow-channel H2O/H2 transport dynamics using micro-scale, non-destructive visualization of spatial and temporal water distribution in the membrane, gas diffusion layer, and flow channel.
i. Neutron transmission imaging
ii. Neutron phase imaging
2. Materials and Nanotechnology
Description: Basic research applicable to many types of fuel cells, aimed at more efficiently functioning electrocatalyst-electrolyte percolation networks for membrane electrode assemblies.
a) Current collectors
Goal: Corrosion resistance
b) Nanostructures
Goals: Improve catalyst utilization, Reduce resistive losses
i. Di- and tri-block copolymers
ii. Mesostructured inorganic solids
iii. Layered thin films
c) Nanoscale catalytic centers
Description: Two-dimensional arrays of nanoscale catalytic centers could enhance the selectivity of membrane permeability, and conversely, the proximity to a selectively permeable barrier could enhance the net activity of integrated catalytic devices.
d) Selectively permeable gas diffusion layers
Description: Develop electronically conducting membranes (such as microporous carbons or hydrogen- permeable metals), or new gas diffusion layer / catalyst architectures, that selectively transport hydrogen and not CO to the catalyst surface.
e) Catalysts
Description: New cathode catalysts are needed to improve system efficiency and to reduce the heat rejection load (which could enable high-temperature PEMFCs, for example).
Goal: Cost, Durability
i. Noble-metal-based catalysts
Description: Develop and evaluate the long-term stability of catalysts other than Pt and Pt alloys that could provide improved mass activity (higher voltage at a given mass-specific current density).
ii. Non-precious-metal catalysts
Description: Effective catalysts not based on precious metals would greatly reduce the cost of fuel cells. Goal: Mass activity > 10% of Pt catalysts (in order to meet volume and weight targets).
a. Nanoparticles
iii. Fundamental analysis
a. Oxygen reduction reaction mechanisms on Pt and Pt alloys
b. Mechanisms in salt and alkaline environments (including gold)
c. Single crystals and surfaces of nanoparticles
d. Durability and degradation mechanisms
iv. Novel catalysts
Goals: Selectivity for the oxygen reduction reaction, Resistance to poisoning, Stability in the fuel cell environment.
a. Intermetallics
b. Mixed oxide-metal phases
c. Supported inorganic compounds
d. Organic compounds
i. Transition-metal macrocyclics
e. Computational modeling and combinatorial methods
Description: Use FTIR imaging to rapidly prepare a large number of noble-metal/metal-oxide, candidate electrocatalysts.
v. Novel support materials Goal: Enhanced corrosion stability
a. Nb-doped TiO2
b. Tungsten-bronzes
c. Stable carbons
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