Due to its high energy density (142 MJ/kg) and ecologically favorable byproduct (water), hydrogen gas is a prospective source of clean energy . Numerous processes, such as water oxidation or splitting (electrolysis , thermolysis, and photocatalytic water splitting ), as well as the use of phototrophic microorganisms (biohydrogen, BioH2) , can be used to produce it. To provide hydrogen to end consumers on demand, the hydrolysis of hydrides, such as sodium borohydride (NaBH4), appears promising .