Catalytic effect of micro/nano-Ni on dehydrogenation performance of Mg₉₀Al₁₀ during air exposure

Air stability is one of the key challenges to be solved in practical application of Mg-based hydrogen storage materials. The dehydrogenation properties and microstructures of air-exposed Mg-Al-based hydrides with micro/nano-Ni added were systematically studied. In a surprise finding, Mg₉₀Al₁₀ with nano-Ni added can maintain excellent low-temperature dehydrogenation performance after air exposure for about 13 days, while the dehydrogenation performance of Mg₉₀Al₁₀ with micro-Ni added gradually deteriorates with the increase of air exposure time. Compared with micro-Ni, nano-Ni particles have smaller size, more uniform dispersion and higher chemical activity, which can effectively promote the desorption of hydrogen. Almost no oxide layer can be found on the surface of nano-Ni particles in the air exposed sample, indicating that it can still maintain excellent chemical activity after air exposure. Furthermore, nano-Ni can evenly coat on the surface of MgH₂ through mechanical milling, which play a key role in inhibiting the adsorption of water and prevent MgH₂ from being excessively oxidized during air exposure. This finding has an important value for the development of highly active and air stable hydrogen storage materials.