Lithium and calcium decorated triphenylene-graphdiyne as potential high-capacity hydrogen storage medium: A first-principles prediction

Recently, a novel layered two-dimensional carbon nanomaterial was synthesized named triphenylene-graphdiyne (TpG). The acetylenic ring and triphenylene are included in primitive cell of this structure. In this work, many different strategies have been adopted to investigate hydrogen storage capacity of Li- and Ca-decorated pristine and B-doped TpG by first-principles calculations. The maximum three H-2 molecules are captured around every one Li atom by Li-decorated on the acetylenic ring only for TpG. The hydrogen storage gravimetric capacity of 8.17 wt% with an approximate ideal average H-2 adsorption energy of 0.18 eV/H-2. Moreover, both acetylenic ring and triphenylene are decorated by Li and two H-2 molecules are adsorbed for each Li atom. The hydrogen storage capacity reaches to 9.70 wt% with an ideal average hydrogen adsorption energy of 0.27 eV/H-2. After two C atoms are doped by B atoms, two more Li atoms are introduced to the triphenylene. Here, maximum 20 H-2 molecules are adsorbed on Li-decorated B-doped TpG. The hydrogen storage capacity reaches to 8.77 wt%, with ideal average hydrogen adsorption energy of 0.24 eV/H-2. Four H-2 molecules can be adsorbed effectively by Ca-decorated pristine TpG with the average hydrogen adsorption energy of 0.19 eV/H-2. We also calculated the H-2 storage of Ca-decorated B-doped TpG and 5.51 wt% of gravimetric with ideal average hydrogen adsorption energy of 0.25 eV/H-2 can be obtained. Our calculation indicates that the Li- and Ca-decorated B-doped TpG and Li-decorated pristine TpG can be a very promising material for reversible hydrogen storage.