Electrochemical hydrogen storage: Achievements, emerging trends, and perspectives

Summary Hydrogen being abundant, eco‐friendly, is a promising alternative energy source to fossil fuels. Its practical application is limited because of difficulty in storage due to low energy density and safety issues. Solid‐state electrochemical hydrogen storage is a promising method among several approaches of hydrogen storage to meet the U.S. Department of Energy's (DOE) targets. Till 2020, no hydrogen storage material has achieved targets due to lack of proper strategies. In view of meeting targets decided by U.S. DOE, a detailed review of whole progress made in electrochemical hydrogen storage approaches and materials is presented. The reported hydrogen storage capacities of Graphene (1.21 wt.%), reduced Graphene Oxide (2.7 wt.%), Mg‐based alloys (up to 7.6 wt.%), hydrogen clathrates (up to 4.2 wt.%), Pervoskite oxides (up to 4 wt.%), and Nd2Sn2O7 (up to 14.86 wt.%) are consolidated at one place and disclosed. The shortcomings hindering current hydrogen storage technologies are summarized and the scope of future improvement in hydrogen storage is outlined. Emerging materials and technologies are mentioned which can progress towards achieving U.S. DOE targets. This review can assist researchers in choosing an appropriate strategy or potential material for electrochemical hydrogen storage. Highlights Achievements in electrochemical hydrogen storage are reviewed. Improvement techniques in conventional electrochemical hydrogen storage are presented in tabular form. Emergences in hydrogen storage materials are listed. Future perspective to meet US DOE targets is decided on basis of review. Hydrogen, the lightest atom, is a promising alternative energy source to fossil fuels but its safe and efficient storage is a challenge. Solid‐state electrochemical hydrogen storage is a promising method among hydrogen storage methods. A detailed review of approaches and materials for electrochemical hydrogen storage is presented.