In situ measurement technologies on solid-state hydrogen storage materials: a review

In an effort to realize a sustainable hydrogen economy, we are facing the demanding and challenging issue of providing compact and safe storage solutions for hydrogen in solid-state materials. Studies on the hydrogen storage properties of materials generally involve their phase structures, microstructures, thermal/structural stability, chemical compositions and bonding, which can be studied by ex situ experimental technologies. However, the experimental results obtained from ex situ measurements may be contaminated during sample handling, and some important intermediate phases are too metastable/unstable to be detected. To overcome the drawbacks, in situ studies are carried out, leading to a large number of unprecedented advantages. In this review, recent advances regarding in situ measurement technologies for solid-state hydrogen storage materials are summarized, mainly focusing on metal hydrides and complex hydrides. The working principles together with the devices used for the in situ methods are briefly introduced. Afterwards, both the classic and recent advances regarding the in situ measurement technologies for metal hydrides and complex hydrides are comprehensively summarized and reviewed. In addition to highlighting the tremendous merits of the in situ methods and the relevant achievements in the field of hydrogen storage materials, the remaining challenges and trends of the emerging research are also discussed.