Physical and electrochemical investigation of hydrogen storage in aluminum hydride nanofibers and high surface area carbon materials.

摘要

In the first part of this dissertation, the investigation of hydrogen storage in aluminum hydride is reported. For the first time, unique aluminum hydride nano fibers were synthesized. The nano-sized AlH3 significantly improves the kinetics for hydrogen desorption. The AlH3 nano-fibers can be decomposed at 85°C whereas the bulk AlH3 decomposes at 130°C. The success makes the use of the hydride feasible for fuel cell application. The exhausted heat from fuel cell can be used to heat the nano size hydride, releasing hydrogen inducing the continuous operation of fuel cells without the need of supplying extra heat.;The most desired form of bulk AlH3 was synthesized by reacting 1:4 molar ratio of AlCl3 and LiAlH4 in ether solution. X-ray diffraction confirmed that the material synthesized was alpha-AlH 3. SEM revealed that the particle size of the material was in the micrometer range. The total hydrogen content of the material was 9.2 % with a purity of 99.999 %.;The AlH3 nanofibers were synthesized by forming the AlH 3 in nano porous activated carbon templates. The diameter of the nanofibers was found in the range of 100 nm as revealed by SEM. The phase of the material was a mixed phase. The best activated carbon for the nano-fiber synthesis was found to be NoritA with average pore size of 25 A° and surface area of 1200 m2/g.;In the second part of this dissertation, the study of electrochemical insertion of hydrogen into a high surface area carbon electrode is reported. The effect of various compounds were investigated as catalytic poison for the hydrogen absorption. Sulfur containing species such as thiourea and L-cystine demonstrated the positive impacts on the electrochemical hydrogen absorption in the carbon electrodes, whereas CN-, As2 O3, and OCN- showed the negative effects. The amount of hydrogen inserted into a carbon electrode was found to be significantly increased (by 30%) with thiourea as a surface catalytic poison. The reversible hydrogen storage capacity was found to be 218 mAh/g (approx. 1 wt %) in M-20 electrode with the charge efficiency of 50 %.