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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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How Pt Influences H 2 Reactions on High Surface-Area Pt/CeO 2 Powder Catalyst Surfaces
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Reactant-Induced Structural Evolution of Pt Catalysts Confined in Zeolite
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Nonthermal Plasma Activation of Adsorbates: The Case of CO on Pt
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Isolated Pt Atoms Stabilized by Ga 2 O 3 Clusters Confined in ZSM-5 for Nonoxidative Activation of Ethane
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Correction to How Pt Influences H 2 Reactions on High Surface-Area Pt/CeO 2 Powder Catalyst Surfaces
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Alloying–realloying enabled high durability for Pt–Pd-3d-transition metal nanoparticle fuel cell catalysts
Abstract Alloying noble metals with non-noble metals enables high activity while reducing the cost of electrocatalysts in fuel cells. However, under fuel cell operating conditions, state-of-the-art oxygen reduction reaction alloy catalysts either feature high atomic percentages of noble metals (>70%) with limited durability or show poor durability when lower percentages of noble metals (<50%) are used. Here, we demonstrate a highly-durable alloy catalyst derived by alloying PtPd (<50%) with 3d-transition metals (Cu, Ni or Co) in ternary compositions. The origin of the high durability is probed by in-situ/operando high-energy synchrotron X-ray diffraction coupled with pair distribution function analysis of atomic phase structures and strains, revealing an important role of realloying in the compressively-strained single-phase alloy state despite the occurrence of dealloying. The implication of the finding, a striking departure from previous perceptions of phase-segregated noble metal skin or complete dealloying of non-noble metals, is the fulfilling of the promise of alloy catalysts for mass commercialization of fuel cells.
Insights into solvent and surface charge effects on Volmer step kinetics on Pt (111)
Abstract The mechanism of pH-dependent hydrogen oxidation and evolution kinetics is still a matter of significant debate. To make progress, we study the Volmer step kinetics on platinum (111) using classical molecular dynamics simulations with an embedded Anderson-Newns Hamiltonian for the redox process and constant potential electrodes. We investigate how negative electrode electrostatic potential affects Volmer step kinetics. We find that the redox solvent reorganization energy is insensitive to changes in interfacial field strength. The negatively charged surface attracts adsorbed H as well as H + , increasing hydrogen binding energy, but also trapping H + in the double layer. While more negative electrostatic potential in the double layer accelerates the oxidation charge transfer, it becomes difficult for the proton to move to the bulk. Conversely, reduction becomes more difficult because the transition state occurs farther from equilibrium solvation polarization. Our results help to clarify how the charged surface plays a role in hydrogen electrocatalysis kinetics.
Understanding hydrogen electrocatalysis by probing the hydrogen-bond network of water at the electrified Pt–solution interface
Rational construction of the electrode–solution interface where electrochemical processes occur is of paramount importance in electrochemistry. Efforts to gain better control and understanding of the interface have been hindered by lack of probing methods. Here, in this study, we show that the hydrogen evolution and oxidation reactions (HER/HOR) catalysed by platinum in base can be promoted by introduction of N-methylimidazoles at the platinum–water interface. In situ spectroscopic characterization together with simulations indicate that the N-methylimidazoles facilitate diffusion of hydroxides across the interface by holding the second layer of water close to platinum surfaces, thereby promoting the HER/HOR. We thus propose that the HER/HOR kinetics of platinum in acid and base is governed by diffusion of protons and hydroxides, respectively, through the hydrogen-bond network of interfacial water by the Grotthuss mechanism. Moreover, we demonstrate a 40% performance improvement of an anion exchange membrane electrolyser by adding 1,2-dimethylimidazole into the alkali fed into its platinum cathode.
Self-supported Pt?CoO networks combining high specific activity with high surface area for oxygen re
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Site-specific reactivity of stepped Pt surfaces driven by stress release
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The role of grain boundary character in solute segregation and thermal stability of nanocrystalline Pt–Au
In nanocrystalline alloys, the anisotropy in grain boundary segregation and its impact on dynamic solute drag plays a key role in the thermal stability of these systems during processing treatments or under service conditions.
Charge pumping enabling Co?NC to outperform benchmark Pt catalyst for pH-universal hydrogen evolutio
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Valence-to-core X-ray emission spectroscopy to resolve the size-dependent valence electronic structure of Pt nanoparticles
X-ray characterization of catalyst materials using synchrotron radiation has become more widely available to the scientific community in recent decades.
Effect of Pt and Ru-based catalysts on the electrochemical hydrodeoxygenation of phenol to cyclohexane
PtRuC offers the opportunity to electrochemically convert bio-oils to drop-in biofuels and platform chemicals. Here we demonstrate the concept using phenol to cyclohexane as a model reaction.