Selective decoration of nitrogenated holey graphene (C2N) with titanium clusters for enhanced hydrogen storage application

For an envisioned hydrogen (H-2) economy, the design of new multifunctional twodimensional (2D) materials have been a subject of intense research for the last several decades. Here, we report the thriving H-2 storage capacity of 2D nitrogenated holey graphene (C2N), functionalized with Ti-n (n = 1-5) clusters. By using spin polarized density functional theory (DFT) calculations implemented with the van der Waals corrections, the most favourable adsorption site for the Tin clusters on C2N has been revealed. With the monomer Ti, the functionalization was evenly covered on C2N having 5% doping concentration (C2N-Ti). For C2N-Ti sheet, Ti binds to C2N with a strong binding energy of similar to 6 eV per Ti which is robust enough to hinder any Ti-Ti clustering. Bader charge analysis reveals that the Tin clusters donate significant charges to C2N sheet and become cationic to polarize the H2 molecules, thus act as efficient anchoring agents to adhere multiple H-2 molecules. Each Ti in C2N-Ti could adsorb a maximum of 10H(2) molecules, with the adsorption energies in the range of-0.2 to-0.4 eV per H-2 molecule, resulting into a high H-2 storage capacity of 6.8 wt%, which is promising for practical H-2 storage applications at room temperature. Furthermore, Ti-m (m = 2, 3, 4, 5) clusters have been selectively decorated over C2N. However, with Tim functionalization H-2 storage capacities fall short of the desirable range due to large molecular weights of the systems. In addition, the H-2 desorption mechanism at different conditions of pressure and temperature were also studied by means of thermodynamic analysis that further reinforce the potential of C2N-Ti as an efficient H-2 storage material. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

The study demonstrates the high H-2 storage capacity of 2D nitrogenated holey graphene functionalized with Ti-n (n = 1-5) clusters, with each Ti capable of adsorbing up to 10 H(2) molecules and achieving a storage capacity of 6.8 wt%. Thermodynamic analysis was conducted to study the H-2 desorption mechanism under different pressure and temperature conditions, further reinforcing the potential of C2N-Ti as an efficient H-2 storage material.