A COMPARATIVE STUDY OF DEHYDROGENATION ENERGETICS OF B2H6, AL2H6 AND GA2H6 BASED ON DENSITY FUNCTIONAL THEORY

The M2H6 molecules, with M=B, Al, Ga, as well as their dehydrogenation derivatives, M2Hn (n = 0 to 5). have been studied using the B3LYP/6-311++G(2d,3p). Based on the optimized minimum energy structures at each n value, we determined reaction energies for the M2H6 -> M2Hn+ 6-n/2 H-2 reactions. These reaction energies represent the low limit of the energy cost to form molecular hydrogen from the corresponding M2H6. Transition state analysis for the first unimolecular step, M2H6 -> M2H4 + H-2, showed that the critical bond for B2H6 dehydrogenation is different from that for Al2H6 and Ga2H6 dehydrogenation although the structure of the transition states appeared to be the same. These transition states lead to the formation of less stable intermediate product states.