Electrochemical hydrogen storage: Opportunities for fuel storage, batteries, fuel cells, and supercapacitors

Solid-state storage of hydrogen is a possible breakthrough to realise the unique futures of hydrogen as a green fuel. Among possible methods, electrochemical hydrogen storage is very promising, as can be conducted at low temperature and pressure with a simple device reversibly. However, it has been overshadowed by the physical hydrogen storage in the literature, and thus, research efforts are not adequately connected to lead us in the right direction. On the other hand, electrochemical hydrogen storage is the basis of some other electrochemical power sources such as batteries, fuel cells, and supercapacitors. For instance, available hydrogen storage materials can build supercapacitors with exceptionally high specific capacitance in order of 4000 F g(-1) In general, electrochemical hydrogen storage plays a substantial role in the future of not only hydrogen storage but also electrochemical power sources. There are some vague points which have obscured our understanding of the corresponding system to be developed practically. This review aims to portray the entire field and detect those ambiguous points which are indeed the key obstacles. It is clarified that different materials have somehow similar mechanisms for electrochemical hydrogen storage, which is initiated by hydrogen dissociation, surface adsorption and probably diffusing deep within the bulk material. This mechanism is different from the insertion/extraction of alkali metals, though battery materials look similar. Based on the available reports, it seems that the most promising material design for the future of electrochemical hydrogen storage is a class of subtly designed nano composites of Mg-based alloys and mesoporous carbons. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.