You-Hua Luo

Graphdiyne: A promising anode material for lithium ion batteries with high capacity and rate capability

We have carried out first-principles calculations to explore the energetics and dynamics of Li in graphdiyne monolayers. The porous structure of graphdiyne enables both in-plane and out-plane diffusion of Li ions with moderate barriers, 0.35–0.52 eV. A unique Li occupation pattern named as a triangular pattern is identified, with Li atoms occupying three symmetric sites in the triangular-like pores. Based on this occupation pattern, the Li storage capacity of single-layer graphdiyne can be as high as LiC3, which is twice the capacity of commonly used graphite (LiC6). With high Li mobility and high storage capacity, this experimentally available porous carbon material is expected to find applications in efficient lithium storage.

Ultra-high hydrogen storage capacity of Li-decorated graphyne: A first-principles prediction

Graphyne, consisting of sp- and sp2-hybridized carbon atoms, is a new member of carbon allotropes which has a natural porous structure. Here, we report our first-principles calculations on the possibility of Li-decorated graphyne as a hydrogen storage medium. We predict that Li-doping significantly enhances the hydrogen storage ability of graphyne compared to that of pristine graphyne, which can be attributed to the polarization of H2 molecules induced by the charge transfer from Li atoms to graphyne. The favorite H2 molecules adsorption configurations on a single side and on both sides of a Li-decorated graphyne layer are determined. When Li atoms are adsorbed on one side of graphyne, each Li can bind four H2 molecules, corresponding to a hydrogen storage capacity of 9.26 wt. %. The hydrogen storage capacity can be further improved to 15.15 wt. % as graphyne is decorated by Li atoms on both sides, with an optimal average binding energy of 0.226 eV/H2. The results show that the Li-decorated graphyne can s...

Single Layer of Polymeric Cobalt Phthalocyanine: Promising Low‐Cost and High‐Activity Nanocatalysts for CO Oxidation

The catalytic behavior of transition metals (Sc to Zn) combined in polymeric phthalocyanine (Pc) is investigated systematically by using first-principles calculations. The results indicate that CoPc exhibits the highest catalytic activity for CO oxidation at room temperature with low energy barriers. By exploring the two well-established mechanisms for CO oxidation with O2 , namely, the Langmuir-Hinshelwood (LH) and the Eley-Rideal (ER) mechanisms, it is found that the first step of CO oxidation catalyzed by CoPc is the LH mechanism (CO + O2 → CO2 + O) with energy barrier as low as 0.65 eV. The second step proceeds via both ER and LH mechanisms (CO + O → CO2 ) with small energy barriers of 0.10 and 0.12 eV, respectively. The electronic resonance among Co-3d, CO-2π*, and O2 -2π* orbitals is responsible for the high activity of CoPc. These results have significant implications for a novel avenue to fabricate organometallic sheet nanocatalysts for CO oxidation with low cost and high activity.

Three-dimensional diffusion of molecular hydrogen in graphdiyne: a first-principles study

First-principles calculations with van der Waals correction included are carried out to investigate the intercalation and diffusion of molecular hydrogen in single-layer and bulk graphdiyne, which is crucial for understanding and improving the hydrogen storage capacity of graphdiyne. Different intercalation sites and hydrogen molecular orientations have been considered and compared. It is found that configurations with the axis of the hydrogen molecule parallel to graphdiyne layers are favoured. In contrast to graphite where hydrogen diffusion is restricted within the interlayer space, the unique porous structure of graphdiyne enables three-dimensional diffusion of hydrogen (in-plane diffusion and out-plane diffusion) with moderate energy barriers, thus ensuring easy hydrogen loading and unloading. The in-plane diffusion barriers largely depend on the interlayer distance, whereas the interlayer spacing has little effect on the out-plane diffusion barriers. This experimentally available novel carbon allotrope is expected to find applications in hydrogen storage.

Ferromagnetism/antiferromagnetism transition between semihydrogenated and fully-aminated single-wall carbon nanotubes

We theoretically studied the ferromagnetism/antiferromagnetism (FM/AFM) transition between single-wall carbon nanotubes (SWCNTs) induced by chemical modifications of semihydrogenation (SH-) and full-amination (NH(2)-). We found that armchairs with large diameters of SH-CNTs (n > 3) possess FM functions with intense magnetic moments, while armchair NH(2)-CNTs (n = 4, 6, 8) are antiferromagnetic semiconductors. The FM/AFM transition is mainly dominated by different chemical modifications and sizes of SWCNTs whose distance between carbon atoms of unpaired electrons can regulate the intensity of p-p spin interactions. Moreover, the zigzag SH-CNTs and NH(2)-CNTs are NM semiconductors. Thus, the electronic and magnetic properties of the SH- or NH(2)-CNTs can be precisely modulated by controlling the hydrogenation or amination on the different types and diameters of CNTs, which provides a new and also simple process for magnetism optimization design in SWCNTs.