Graphitic carbon nitride (g-C3N4) decorated with Yttrium as potential hydrogen storage material: Acumen from quantum simulations

Abstract

With the aid of the state-of-the-art Density Functional Theory simulations, triazine-like graphitic carbon nitride or g-C3N4 (abbreviated as gCN hereafter) nanosheet decorated with Y has been explored for reversible hydrogen storage applications in light fuel cell vehicles. The Y atom is found to bind strongly with gCN (binding energy ∼ −6.85 eV), can reversibly store 9 H2 with an average adsorption energy of −0.331 eV/H2, an average desorption temperature of 384.24 K, and a storage capacity of 8.55% by weight, optimum for fuel cell application as prescribed by the Department of Energy. The bonding of Y on gCN involves a charge transfer from Y 4d orbitals to C and N 2p orbitals, whereas the adsorption of H2 is due to Kubas interactions involving net charge transfer from Y 4d orbital to H 1s orbital. We have computed the diffusion energy barrier for Y atoms as 3.07 eV, which may prevent metal-metal clustering. Further, ab-initio molecular dynamics simulation has been performed to check the structural stability of the present system. The system is found to be stable at 500 K with different concentrations of Y doping. The present system with the appropriate average adsorption energy per H2, suitable desorption temperature, and structural stability at higher temperatures is promising for onboard light fuel cell applications.