Decomposition Mechanism of Zinc Ammine Borohydride: A First-Principles Calculation

The decomposition mechanism of zinc ammine borohydride ([Zn(NH 3 ) 2 ][BH 4 ] 2 ) has been studied by density functional theory calculation. The release of B 2 H 6 and BH 3 is predicted to be kinetically and/or thermodynamically unfavorable for [Zn(NH 3 ) 2 ][BH 4 ] 2 , in agreement with experimental results that no boranes were detected during decomposition. The climbing image nudged elastic band calculation and ab initio molecular dynamics simulations indicate the formation of NH 3 BH 3 and B 2 H 7 - intermediates during decomposition of [Zn(NH 3 ) 2 ][BH 4 ] 2 , which is different from that observed for other reported ammine metal borohydrides. The dehydrogenation occurs through reaction pathways involving transfer of hydrides from the Zn cation to BH 4 - or transfer of protons from NH 3 BH 3 to NH 3 .