Assisting Ni catalysis by CeO2 with oxygen vacancy to optimize the hydrogen storage properties of MgH2

Although MgH2 has been widely regarded as a promising material for solid-state hydrogen storage, its high operating temperature and slow kinetics pose a major bottleneck to its practical application. Here, a nanocomposite catalyst with interfacial coupling and oxygen defects, Ni/CeO2, is fabricated to promote H-2 desorption and absorption properties of MgH2. The interface of Ni/CeO2 contributes to both strong mechanical coupling towards stabilizing partial Ni and electronic coupling towards inducing a high concentration of oxygen vacancies in CeO2. Theoretical calculations evidence that CeO2 with oxygen vacancy assist Ni in weakening the energy of Mg-H bond as well as enhancing the adsorption energy of Ni upon hydrogen atoms, and the extent of this assistance surprisingly increases with increasing oxygen vacancies concentration. As a result, an impressive performance is achieved by MgH2-5 wt.% Ni/CeO2 with onset desorption temperature of only 165 degrees C, and it absorbs approximately 80% hydrogen in just 800 s at 125 degrees C. The generation mechanism of intermediate active species concerning Ni/CeO2 in different states has been analyzed for the first time, and the relationship between interfacial coupling and phase evolution has been elucidated. Therefore, a mechanism of the catalysis-assisting effect regarding oxygen defects is proposed. It is believed that this work provides a unique perspective on the mechanism of interfacial coupling and the generation of defects in composite catalysts. (c) 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.