Computational study of catalytic effect of C3N4 on H2 release from complex hydrides

The interaction between C₃N₄ and three kinds of complex hydrides, LiAlH₄, LiBH₄, and NaAlH₄, was investigated through density functional theory (DFT) computations. The adsorption of LiAlH₄, LiBH₄, and NaAlH₄ is much stronger on C₃N₄ than other traditional carbon materials, such as graphene, carbon nanotubes, and fullerenes. Such strong interaction causes the electron redistribution in complex hydrides, and destabilizes Al/B–H bonds indirectly, thereby reducing the hydrogen removal energy. Moreover, C₃N₄ provides a very suitable adsorption site for AlH_x/BH_x (x = 3, 2, 1) units by the bond formation between Al/B and N atoms after losing H atoms. For the first step of dehydrogenation, due to the presence of C₃N₄, the H-removal energies decrease significantly. In addition, the adsorption energy of H₂ molecule on C₃N₄ is so low that C₃N₄ would not capture the released H₂ from complex hydrides. Therefore, C₃N₄ is a potential catalyst for H₂ release from complex hydrides.