Electrolytic Hydrogen Release from Hydrogen Boride Sheets.

Solid-state hydrogen storage materials are safe and lightweight hydrogen carriers. Among the various solid-state hydrogen carriers, hydrogen boride (HB) sheets possess a high gravimetric hydrogen capacity (8.5 wt%). However, heating at high temperatures and/or strong ultraviolet illumination is required to release hydrogen (H) from HB sheets. In this study, the electrochemical H release from HB sheets using a dispersion system in an organic solvent without other proton sources is investigated. H molecules are released from the HB sheets under the application of a cathodic potential. The Faradaic efficiency for H release from HB sheets reached >90%, and the onset potential for H release is -0.445 V versus Ag/Ag, which is more positive than those from other proton sources, such as water or formic acid, under the same electrochemical conditions. The total electrochemically released H in a long-time experiment reached ≈100% of the hydrogen capacity of HB sheets. The H release from HB sheets is driven by a small bias; thus, they can be applied as safe and lightweight hydrogen carriers with economical hydrogen release properties.