Hydrogen storage on graphitic carbon nitride and its palladium nanocomposites: A multiscale computational approach

Hydrogen storage capacity (HSC) of multilayer graphitic carbon nitride, d-g-C3N4 (d is interlayer spacing), and its palladium nanocomposite, d-Pd@g-C3N4, were investigated using multiscale computational techniques including quantum mechanics calculations and grand canonical Monte Carlo (GCMC) simulation. According to the results, the volumetric HSC of 8-g-C3N4 and 8-Pd@g-C3N4 can reach to DOE target of 30 gH(2)/L at 177 K, 5.7 MPa, and 177 K, 4.0 MPa, respectively. The gravimetric HSC of 10-g-C3N4 and 12-Pd@g-C3N4 meet the DOE target of 4.5 wt% at 150 K, 3.5 MPa, and 125 K, 4.0 MPa, respectively. The incorporation of Pd atoms enhances the delivery volumetric HSC of 6-, 8-, 10-, and 12-g-C3N4 by 49, 55, 129, and 146%, respectively at 177 K and 0.5 MPa. On the other hand, the incorporation of Pd atoms has a negative effect on the delivery gravimetric HSC of 6- and 8-g-C3N4 and positive effect for 10- and 12-g-C3N4. The estimated isostric heat, Q(st), of adsorption is 5.5-8.5 kJ/mol. The maximum value of Q(st) for both nanoadsorbents belong to those with d = 8 angstrom. The structure of adsorbates and possibility of multilayer adsorption occurrence were also investigated using pair correlation functions and density profiles. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.