Phys Chem Chem Phys, 26, 9586 (2024)
Dehydrogenation of Diborane on Small Nbn+ Clusters
Wen Gan1, Lijun Geng1, Benben Huang1, Klavs Hansen3 and Zhixun Luo1,2,*
1 Beijing National Laboratory for Molecular Science, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.
2 School of Chemical Science, University of Chinese Academy of Sciences, Beijing 100049, China
3 Center for Joint Quantum Studies and Department of Physics, School of Science, Tianjin University, 92 Weijin Road, Tianjin 300072, China
* zxluo@iccas.ac.cn
Abstract
The reactivity of Nbn+ (1 r n r 21) clusters with B2H6 is studied by using a self-developed multiple-ion laminar flow tube reactor combined with a triple quadrupole mass spectrometer (MIFT-TQMS). The Nbn+ clusters were generated by a magnetron sputtering source and reacted with the B2H6 gas under fully thermalized conditions in the downstream flow tube where the reaction time was accurately controlled and adjustable. The complete and partial dehydrogenation products NbnB1–4+ and NbnB1–4H1,2,4+ were detected, indicative of the removal of H2 and likely BHx moieties. Interestingly, these NbnB1–4+ and NbnB1–4H1,2,4+ products are limited to 3 r n r 6, suggesting that the small Nbn+ clusters are relatively more reactive than the larger Nbn46+ clusters under the same conditions. By varying the B2H6 gas concentrations and the reactant doses introduced into the flow tube, and by changing the reaction time, we performed a detailed analysis of the reaction dynamics in combination with the DFTcalculated thermodynamics. It is demonstrated that the lack of cooperative active sites on the Nb1+ cations accounts for the weakened dehydrogenation efficiency. Nb2+ forms partial dehydrogenation products at a faster rate. In contrast, the Nbn46+ clusters are subject to more flexible vibrational relaxation which disperse the energy gain of B2H6-adsorption and thus are unable to overcome the energy barriers for subsequent hydrogen atom transfer and H2 release.
