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• A series of Ti-Zr-Hf-Mo-Nb HEA alloys with single BCC structure were developed. • Cell volume of Ti-Zr-Hf-Mo-Nb alloys decrease with increasing Mo concentration. • The decreased cell volume reduces the thermal stability of Ti-Zr-Hf-Mo-Nb hydrides. • The stability of Ti-Zr-Hf-Mo-Nb hydride is positively related to binding energy. • The Ti-Zr-Hf-Mo-Nb HEA alloys could be candidate materials for hydrogen storage. A series of Ti-Zr-Hf-Mo-Nb high-entropy alloys with different Mo concentrations were developed as candidate materials for hydrogen/tritium storage in solid phase. The crystal structures and hydrogenation properties of the Ti-Zr-Hf-Mo-Nb alloys were investigated by X-ray diffraction and differential scanning calorimetry techniques. All the alloys have a body-centred cubic single phase structure. The results demonstrate that the cell volume of the Ti-Zr-Hf-Mo-Nb hydride decreases with increasing Mo concentration, which reduces their thermal stability. The theoretical calculation proposes that the lower binding energy of the Ti-Zr-Hf-Mo-Nb hydride decreases the thermal stability of Ti-Zr-Hf-Mo-Nb alloys with higher Mo content. The great hydrogenation performance for all the Ti-Zr-Hf-Mo-Nb alloys is owing to their reversible single-phase transformation during the hydrogen absorption-desorption cycle, which would be beneficial to improving the hydrogen recycling rate and preventing the disproportionation. The compositional dependence of the hydrogenation performance of the Ti-Zr-Hf-Mo-Nb alloys was established and will be useful in designing novel hydrogen/tritium storage materials to satisfy the requirements of different application fields in hydrogen, solar thermal and nuclear energy. [ABSTRACT FROM AUTHOR]