Li decorated graphene is supposed to be a promising material for the hydrogen storage, which can be further improved by heteroatom doping. But a unified promoting mechanism for various doping types and species are still lacking, which hinders the rational design of advanced materials. The potential of N/B doped Li decorated graphene for hydrogen storage is investigated with DFT calculations. A covalent interaction between Li and the graphene substrates is identified to control the thermostability and hydrogen storage capacity (HSC) of the Li decorated substrate, which is in turn subject to the electronegativity of doping species and the doping types. Additionally, a conceptual descriptor is proposed to predict the HSC of Li decorated graphene. These results provide a unified explanation and prediction of the effects of heteroatom doping on Li decorated carbon materials for hydrogen storage. (c) 2017 Elsevier B.V. All rights reserved.