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The 12 wt% Pt-deposited carbon nanotube electrode gives 10% higher voltages than 29 wt% Pt-deposited carbon black and reduces the Pt usage by 60% in polymer electrolyte fuel cells with hydrogen and oxygen.

Atomic hydrogen storage by carbon nanotubes (CNTs) at atmospheric pressure is studied using Pd and La catalysts for dissociation of H 2 into atomic hydrogen and formation of defects on CNT surfaces, respectively. The defect sites on CNTs as adsorption sites of atomic hydrogen are prepared by oxidation pretreatment using a La catalyst. Pd catalysts are then deposited on CNT surfaces for dissociation of H 2 into atomic hydrogen, which then spills over to the defect sites. In the best case, 1.0 wt % hydrogen is stored in the defective CNT with Pd particles at 1 atm and 573 K. The hydrogen desorption in temperature programmed desorption (TPD) experiments started at 700-900 K, which agreed with the annealing temperatures of CNTs prior to hydrogen storage. Also, the amount of hydrogen stored in CNTs decreased with increasing annealing temperature. These results are ascribed to the crystallization of the defective structure of CNT into graphitic structure. The activation energies of 46.6, 87.3, and 129.8 kJ/mol derived from the desorption peaks of hydrogen in the defective CNT with Pd particles vary from 46.6 to 129.8 kJ/mol, depending on the annealing temperatures at 523, 623, and 773 K, respectively. The difference in the activation energies is probably due to the energies required for the recrystallization of the defect sites into the graphite structure.

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Nitrogen-vacancy (NV) centers in diamond have attracted significant interest because of their excellent spin and optical characteristics for quantum information and metrology. To take advantage of the characteristics, the precise control of the orientation of the N-V axis in the lattice is essential.Here we show that the orientation of more than 99 % of the NV centers can be aligned along the [111]axis by CVD homoepitaxial growth on (111)-substrates. We also discuss about mechanisms of the alignment. Our result enables a fourfold improvement in magnetic-field sensitivity and opens new avenues to the optimum design of NV center devices.