Cobalt (II) salts, performing materials for generating hydrogen from sodium borohydride

Hydrogen generation through sodium borohydride (NaBH4) hydrolysis has attracted much attention. This reaction has to be catalyzed by metal-based materials. We studied the catalytic potential of cobalt (II) and (III) salts. Some of them have never been studied, and compared to e.g. cobalt nanoparticles or powder, and cobalt borides. CoCl2 showed the best performance. In our opinion, CoCl2 should not be dismissed from the large number of catalysts. One could conceive portable applications using CoCl2; this is briefly discussed. CoCl2 was compared to both commercial cobalt boride and in-situ formed (through our hydrolysis conditions) cobalt boride. Their hydrogen generation rates were 86.3, 1.0 and 1.6 L min−1 g−1(Co), respectively. The hydrogen generation rate of CoCl2 is one of the highest ones reported so far. It is assumed that cobalt boride surface evolves during the reaction and depends on the hydrolysis medium features. Further studies are required to fully explain the complex reaction mechanisms.