Enhanced hydrogen adsorption-desorption reversibility found on NiAl alloy: A first-principles study

Abstract

Improving the hydrogen storage performance of carbon-based materials via transition metals incorporation has been proved experimentally, where control over the hydrogen adsorption kinetics and hydrogen surface diffusion is the key. In this work, we proved theoretically via density functional theory (DFT) how such incorporation promotes better hydrogen storage performance in Ni-based materials supported on graphene, in which static and dynamic behavior of the system were modeled by plane-wave DFT and ab initio molecular dynamics (AIMD), respectively. In addition, the hydrogen storage materials Ni10Al3 and Ni13 supported on graphene, denoted as Ni10Al3/GP and Ni13/GP, are modeled to realize the experimental observation on Ni3Al alloy under high hydrogen pressure. It was found that the Ni10Al3/GP alloy system exhibited better properties in twofold: (1) increased hydrogen adsorption capacity through providing an additional site for H2 molecular adsorption, particularly on the Al atoms, and (2) enhanced hydrogen desorption at ambient conditions observed from reversible H2 adsorption at all coverages with barrierless migration energy. Therefore, the proof from the DFT point-of-view provides valuable insight into exploring other metal alloy systems that can provide additional sites for molecular hydrogen adsorption and improve hydrogen adsorbate mobility.