摘要
The vacancy defect exhibits a remarkable improvement in the dehydriding property of MgH_(2)@Ni-CNTs.However,the corresponding mechanism is still not fully understood.Herein,the impact of vacancy defects on the dehydrogenation properties of MgH_(2)@Ni-CNTs was studied by DFT simulation,and the corresponding models were constructed based on MS.The dehydrogenation process of MgH_(2)can be regarded as the dissociation of Mg-H and desorption of H_(2)from the MgH_(2)surface.In view of the whole dehydrogenation,the dissociation of H^(−)is the rate-determining step,which is the main reason for restricting the dehydrogenation kinetics.Compared with vacancy vacancy-defective MgH_(2)(001)surface,the appearance of vacancy defects on the(110)surface substantially reduces the energy barrier required for H dissociation to 0.070 Ha.The reason is that vacancy defects accelerate the transition of electrons from the H^(−)s orbit to the Mg^(2+)3s orbit,resulting in a decrement of the Mg-H bond strength,which makes H atoms more easily dissociated from the MgH_(2)(110)surface.Therefore,the existence of vacancy defects improves the dehydriding kinetic of MgH_(2).Most importantly,this research offers crucial directions for developing hydrogen storage materials as well as a potential fix for the slow dehydrogenation kinetics of nano-confined MgH_(2).
基金
financed by the National Key Research and Development Program of China(Grant No.2021YFB3802400)
the National Natural Science Foundation of China(Grants Nos.52071141,52271212,52201250,and 51771056)
the Natural Science Foundation of Hebei Province(Grant No.E2018502054)
the Fundamental Research Funds for the Central Universities(Grant No.2023MS148).
