Hydrogen Storage by Polylithiated Molecules and Nanostructures

We study polylithiated molecules as building blocks for hydrogen storage materials, using first-principles calculations. CLi4 and OLi2 bind 12 and 10 hydrogen molecules, respectively, with an average binding energy of 0.10 and 0.13 eV, leading to gravimetric densities of 37.8 and 40.3 wt % of H2. Bonding between Li and C or O is strongly polar and H2 molecules attach to the partially charged Li atoms without dissociating, which is favorable for (de)hydrogenation kinetics. CLin and OLim molecules can be chemically bonded to graphene sheets to hinder the aggregation of such molecules. In particular B- or Be-doped graphene strongly bind the molecules without seriously affecting the hydrogen binding energy. This still leads to a hydrogen storage capacity in the range of 5−8.5 wt % of H2.

本研究采用第一性原理计算方法，以多锂化分子作为储氢材料的构筑基元开展系统探究。CLi4与OLi2可分别结合12个和10个氢分子，对应平均结合能分别为0.10 eV与0.13 eV，其氢重量储氢密度可达37.8 wt%与40.3 wt%。锂与碳或氧之间的成键具有强极性特征，氢分子会吸附于带部分电荷的锂原子表面且不发生解离，这一特性有利于加氢与脱氢反应的动力学过程。CLin与OLim分子可通过化学键合方式负载于石墨烯片层之上，以抑制此类分子的团聚现象。尤为关键的是，掺硼或掺铍石墨烯可与上述分子形成强结合作用，且不会显著影响氢分子的结合能，最终仍可使体系实现5~8.5 wt%的储氢容量。