Magnesium (hydride) is a promising system for the reversible on-board storage of hydrogen, but suffers from slow sorption kinetics and a high thermodynamic stability of the hydride. We explored a combined approach to tackle these problems: nanosizing and carbon-supporting the magnesium, and doping it with nickel. Samples were prepared by melt infiltration with magnesium of nanoporous carbon onto which 1-12 wt% nickel nanoparticles had been predeposited. For loadings up to 15 wt% MgH2, 10-30 nm crystallites with different compositions were formed inside the porous carbon, each giving a specific H2 desorption signature. Surprisingly, higher Mg loadings resulted in more homogeneously mixed samples, which was due to the facilitated wetting of the carbon with the magnesium due to the presence of nickel. Hydrogen release temperatures close to that of Mg2NiH4 were observed for high MgH2 loadings (50 wt%) and small amounts of Ni (Mg(0.95)Ni(0.05)). The favourable H2 desorption properties could mainly be attributed to excellent kinetics due to the efficient mixing of magnesium, nickel and carbon on the nanoscale.
Cobalt phthalocyanine (CoPc) and iron phthalocyanine (FePc) are possible oxygen reduction catalysts in fuel cells, but the exact functioning and deactivation of these catalysts is unknown. The electronic structure of the CoPc and FePc has been studied in situ under hydrogen and oxygen atmospheres by a combination of ambient-pressure X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. The results show that when oxygen is introduced, the iron changes oxidation state while the cobalt does not. The data show that oxygen binds in an end-on configuration in CoPc, while for FePc side-on binding is most likely
Lanthanum oxide-based catalysts are active in the elimination of HCl from C 2 H 5 Cl, 1,2-C 2 H 4 Cl 2 and 1,1,2-C 2 H 3 Cl 3 leading to the formation of their respective chlorinated ethenes. An oxygen-rich catalytic surface may form CO, CO 2 and C 2 HCl as side products, whereas with chlorine-rich catalytic surfaces a stable product distribution is achieved with 100% selectivity towards the formation of ethenes, such as the valuable C 2 H 3 Cl intermediate.
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