9 research outputs found
A study of RhxSy/C and RuSex/C as methanol-tolerant oxygen reduction catalysts for mixed-reactant fuel cell applications
No full textReprint of “A study of RhxSy/C and RuSex/C as methanol-tolerant oxygen reduction catalysts for mixed-reactant fuel cell applications”
No full text
Coadsorption of sodium and elemental sulfur on nickel (100) surfaces, 1996
No full textThis study examined the structural and electronic growth properties of the coadsorption of Sodium and elemental Sulfur on Nickel (100) surfaces at room temperature. The investigation was conducted in an ultra high vacuum system using low energy electron diffraction, Auger electron spectroscopy, and work function measurements. The main objective of the study was to create a low work function substrate that would be useful for low work function devices. The research occurred in four stages: (1) adsorption of S on clean Ni(100), (2) adsorption of Na on clean Ni(100), (3) coadsorption of Na on S covered Ni(100), and (4) coadsorption of S on Na covered Ni(100). The measurements obtained suggest that S grows on Ni(100) in a layer by layer mode, forming a p(2x2) initially and a c(2x2) at the completion of the first layer. The second layer of S is disordered. The measurements also indicate that deposition of Na at room temperature forms a single c(2x2) layer. The coadsorption studies showed that the presence of S on the surface of Ni(100) increased the amount of Na that can be deposited on the substrate. A low work function of 0.8eV was obtained during the study. Furthermore, the presence of Na on Ni(100) was found not to affect the deposition of S, however the S was found to destroy the metallic character of the underlying Na
Highlighting DOE EERE Efforts for the Development of SOFC Systems for APU and Stationary Applications
No full textHydrogen and Fuel Cell Technology: Progress, Challenges, and Future Directions
No full textAbstractThe Department of Energy's (DOE) hydrogen and fuel cell activities are presented, focussing on key targets and progress. Recent results on the cost, durability, and performance of fuel cells are discussed, along with the status of hydrogen-related technologies and cross-cutting activities. DOE has deployed fuel cells in key early markets, including backup power and forklifts. Recent analyses show that fuel cell electric vehicles (FCEVs) are among the most promising options to reduce greenhouse gas emissions and petroleum use. Preliminary analysis also indicates that the total cost of ownership of FCEVs will be comparable to other advanced vehicle and fuel options
State-resolved gas-surface reactivity of methane in the symmetric C-H stretch vibration on Ni(100)
No full textThe state-resolved reactivity of CH4 in its totally symmetric C-H stretch vibration (�1) has been
measured on a Ni(100) surface. Methane molecules were accelerated to kinetic energies of 49 and
63:5 kJ=mol in a molecular beam and vibrationally excited to �1 by stimulated Raman pumping before
surface impact at normal incidence. The reactivity of the symmetric-stretch excited CH4 is about an order
of magnitude higher than that of methane excited to the antisymmetric stretch (�3) reported by Juurlink
et al. [Phys. Rev. Lett. 83, 868 (1999)] and is similar to that we have previously observed for the excitation
of the first overtone (2�3). The difference between the state-resolved reactivity for �1 and �3 is consistent
with predictions of a vibrationally adiabatic model of the methane reaction dynamics and indicates that
statistical models cannot correctly describe the chemisorption of CH4 on nickel
Efficient Stimulated Raman Pumping for Quantum-State Resolved Surface Reactivity Measurements
No full textWe describe the use of stimulated Raman pumping in a molecular beam to perform quantum state resolved gas-surface reactivity measurements for molecules prepared in totally symmetric vibrational states. Vibrational states of homonuclear diatomics as well as totally symmetric vibrations of polyatomic molecules cannot be prepared by direct infrared excitation but are accessible through stimulated Raman pumping by two laser fields when the difference between the incident laser frequencies matches the vibration. We generate a suitable resonant pair of high-energy pump and Stokes laser beams in an injection seeded Raman amplifier filled with the sample gas and equipped with internal gas recirculation. The ability to partially saturate the Raman pumping process in the molecular beam is used to quantify the fraction of vibrationally excited molecules in the irradiated volume, which is needed for quantitative reactivity measurements. We illustrate the method with state resolved reactivity measurements for CH4, prepared in its symmetric C-H stretch vibration on a Ni(100) single crystal surface.LCP
U.S. DOE Progress Towards Developing Low-Cost, High Performance, Durable Polymer Electrolyte Membranes for Fuel Cell Applications
No full textLow cost, durable, and selective membranes with high ionic conductivity are a priority need for wide-spread adoption of polymer electrolyte membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs). Electrolyte membranes are a major cost component of PEMFC stacks at low production volumes. PEMFC membranes also impose limitations on fuel cell system operating conditions that add system complexity and cost. Reactant gas and fuel permeation through the membrane leads to decreased fuel cell performance, loss of efficiency, and reduced durability in both PEMFCs and DMFCs. To address these challenges, the U.S. Department of Energy (DOE) Fuel Cell Technologies Program, in the Office of Energy Efficiency and Renewable Energy, supports research and development aimed at improving ion exchange membranes for fuel cells. For PEMFCs, efforts are primarily focused on developing materials for higher temperature operation (up to 120 °C) in automotive applications. For DMFCs, efforts are focused on developing membranes with reduced methanol permeability. In this paper, the recently revised DOE membrane targets, strategies, and highlights of DOE-funded projects to develop new, inexpensive membranes that have good performance in hot and dry conditions (PEMFC) and that reduce methanol crossover (DMFC) will be discussed
