Ab initio investigation of hydrogenation of (BN)16: A comparison with that of (BN)12

The hydrogenation of B16N16 cage has been studied using ab initio molecular orbital theory with B3LYP/6-31G(d) method. The structure characters of the most stable B16N16Hn (n = 2-32) isomers are discussed in detail. The results show that the average binding energies of hydrogenated B16N16 cage are smaller than that of B12N12 cage especially in high hydrogen coverage. The smaller angle distortion and shorter average B-N bond length of B16N16 are the main reason for the smaller average binding energy per H2 of B16N16Hn comparing with B12N12Hn. Gibbs free energy calculation shows the reaction of B16N16 + 16H2 → B16N16H32 will reverse at about 110 K, which is lower than the reversing temperature 320 K for the reaction of B12N12 + 12H2 → B12N12H24.