Cobalt boride catalysts for small-scale energy application

• Co3O4 for NaBH4 hydrolysis was synthesized by calcination of cobalt salts.
• The catalyst active component forms from Co3O4 upon its contact with NaBH4 medium.
• The more defects are present in Co3O4 structure the faster the rate of its reduction.
• The most active Co3O4 from CoCl2 was chosen to prepare solid state NaBH4 pellets.
• For the first time they were used as H2 source in thermo-electrical energy convertor.

The objects of investigation were cobalt boride catalysts for a one-step production of hydrogen from NaBH4. Cobalt oxides prepared by calcination of cobalt salts at 500 °C were used as precursors of the catalyst active phase. It was shown that the nature of the cobalt oxide precursor has a substantial influence on the rate of formation of active component in the reaction medium of sodium borohydride and, hence, on its activity in NaBH4 hydrolysis. The length of the activation period and catalytic activity do not correlate with the dispersion and the specific surface area of the synthesized Co3O4 samples but depend on their inhomogeneity and the defect structure of the oxide due to the distribution of cobalt ions in the crystal lattice. The more defects are present in of Co3O4 the faster the rate of its reduction and, hence, the higher its catalytic activity in NaBH4 hydrolysis.On the basis of active oxide prepared from cobalt chloride, solid state NaBH4 pellets have been prepared. For the first time, NaBH4 pellets were used as a source of H2 source for a thermo-electrical energy conversion device based on combustion technologies.

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