Hydrogen storage in Li decorated and defective pentaoctite phosphorene: A density functional theory study

Hydrogen storage in 2D pentaoctite phosphorene was investigated by density functional theory (DFT) calculations. Defect engineering and Li decoration were adopted to evaluate their effects on the hydrogen storage. The formation energies for two types of point de-fects, single vacancy (SV) and double vacancy (DV) were calculated. The DFT results showed that pristine pentaoctite had a very weak binding with H2 molecule. With the defect formation energies in the order of black phosphorene, the point defects marginally improved the binding energy of H2 molecule. However, Li decoration over pristine and defective substrates enhanced the binding energy of H2 molecule by 5-10 fold improving from around-0.03 eV/H2 to-0.25 eV/H2, thereby, resulting a better H2 storage capacity. PDOS calculation evidenced the charge transfer from Li atom as its key attribute. In addition, multiple Li adatoms were decorated over the substrate at the favorable sites. In Li decorated pristine, SV, and DV defective substrates, up to 5, 6, and 3 H2 molecules could be absorbed at each Li adatom. The diffusion energy barrier of Li from one favorable site to another was calculated to be an order of magnitude higher that its thermal energy causing an impedance to clustering. (c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

Hydrogen storage in 2D pentaoctite phosphorene was investigated via density functional theory (DFT) calculations. Defect engineering and Li decoration were found to enhance the hydrogen storage capacity. Li decoration significantly improved the binding energy of H2 molecule, resulting in a better storage capacity. Multiple H2 molecules could be absorbed at each Li adatom, and clustering was impeded by the high diffusion energy barrier of Li.