The most frequently reported substance classes for hydrogen storage selected from 2011-2021 publications are summarized in Figure . The development of hydrogen storage materials can be divided in two periods, steady 2011-2015 with a slight increase in 2013, ups and downs during 2016-2021 with a visible decrease in 2020. Three main substance classes such as alloys, general inorganic, and small organic/inorganic molecules continued to be a focus of hydrogen storage research. During the 2011-2015 period, publications on alloys dominated since alloys were used for both physical storage (tanks/pipelines materials) and chemical storage (sorbents). It is interesting that research on polymers also increased at that time due to polymer reinforcement of metal storage tanks. New interest in polymers appeared in 2021 when porous polymers able reversibly stored and released hydrogen were reported. Coordination compounds, which were of great interest in 2011-2015, show a decline in 2016-2021. There is continuous attention to hydrides with a surge in 2021. Elements and oxides are always in the spotlight. Those substances represent carbonaceous sorbents, dehydrogenation catalyst and modifiers.