R. B. Penland

Bio: R. B. Penland is an academic researcher. The author has contributed to research in topics: Infrared spectroscopy & Urea. The author has an hindex of 1, co-authored 1 publications receiving 235 citations.

Zirconium nitride catalysts surpass platinum for oxygen reduction

Abstract: Platinum (Pt)-based materials are important components of microelectronic sensors, anticancer drugs, automotive catalytic converters and electrochemical energy conversion devices1. Pt is currently the most common catalyst used for the oxygen reduction reaction (ORR) in devices such as fuel cells and metal–air batteries2,3, although a scalable use is restricted by the scarcity, cost and vulnerability to poisoning of Pt (refs 4–6). Here we show that nanoparticulate zirconium nitride (ZrN) can replace and even surpass Pt as a catalyst for ORR in alkaline environments. As-synthesized ZrN nanoparticles (NPs) exhibit a high oxygen reduction performance with the same activity as that of a widely used Pt-on-carbon (Pt/C) commercial catalyst. Both materials show the same half-wave potential (E1/2 = 0.80 V) and ZrN has a higher stability (ΔE1/2 = −3 mV) than the Pt/C catalyst (ΔE1/2 = −39 mV) after 1,000 ORR cycles in 0.1 M KOH. ZrN is also shown to deliver a greater power density and cyclability than Pt/C in a zinc–air battery. Replacement of Pt by ZrN is likely to reduce costs and promote the usage of electrochemical energy devices, and ZrN may also be useful in other catalytic systems. Platinum catalysts are widely used for oxygen reduction reactions in electrochemical devices but scalability is restricted by scarcity, cost and vulnerability to poisoning. Zirconium nitride nanoparticles now exhibit an oxygen reduction performance with similar activity to that of Pt on carbon.

Heavy-Ion Radiobiology: Cellular Studies

Abstract: LBL~11861 Preprintc MAY 17 LIBRARY AND To be published as a chapter in ADVANCES IN RADIATION BIOLOGY, Spring/Summer 1983, J.T. Lett, ed., Academic Press, New York, NY HEAVY-ION RADIOBIOLOGY: CELLULAR STUDIES Eleanor A. Blakely, Frank Q.H. Ngo, Stanley B. Curtis, and Cornelius A. Tobias February 1983 This a Library Circulating Copy which may be two weeks. a personal Division)' Prepared for the U.S. Department of Energy under Contract DE-AC03-76SF00098

Dissociation rates of urea in the presence of NiOOH catalyst: a DFT analysis.

Abstract: Single molecule reactions have been studied between nickel oxyhydroxide, urea, and the hydroxide ion to understand the process of urea dissociation into ammonia, isocyanic acid, cyanate ion, carbon dioxide, and nitrogen. In the absence of hydroxide ions, nickel oxyhydroxide will catalyze urea to form ammonia and isocyanic acid with the rate-limiting step being the formation of ammonia with a rate constant of 1.5 × 10⁻⁶ s⁻¹. In the presence of hydroxide, the evolution of ammonia was also the rate-limiting step with a rate constant of 1.4 × 10⁻²⁶ s⁻¹. In addition, desorption of the cyanate ion presented an energy barrier of 6190 kJ mol⁻¹ suggesting that the cyanate ion cannot be separated from NiOOH unless further reactions occurred. Finally, elementary dissociation reactions with hydroxide ions deprotonating urea to produce nitrogen and carbon dioxide were analyzed. These elementary reactions were investigated along three paths differing in the order that protons were removed and the nitrogen atoms were rotated. The rate-limiting step was found to be the removal of carbon dioxide with a rate constant of 4.3 × 10⁻⁶⁵ s⁻¹. Therefore, the catalyst could be deactivated by the surface blockage caused by carbon dioxide adsorption.

Characterization of La0.67Ca0.33MnO3±δ particles prepared by the sol–gel route

Abstract: We report in this work the characterization of La0.67Ca0.33MnO3±δparticles synthesizedvia sol–gel technology starting from an aqueous solution of the metallic nitrates and using urea as gelificant agent. The gelification is assumed to happen through the formation of polynuclear species by condensation reactions between hydroxo complexes. Gels were decomposed at 250 °C and calcined for 3 h at temperatures ranging from 300 to 1000 °C. Complete crystallization takes place at ca. 600 °C. The powders were structurally characterized by X-ray diffraction and their structural parameters were calculated using the Rietveld method. The MnIV content of the several samples was determined to be higher than the stoichiometric 33%. TEM micrographs show elongated particles of which the polar (long) axis size increases from 40 to 300 nm as the calcination temperature increases. Magnetization and magnetoresistance studies are reported showing that the particles smaller than 80 nm behave as single magnetic domains while the large ones behave as multidomains. A magnetoresistance of 12% at 1 kOe was observed for all the particles synthesized by this sol–gel method.