Effects of crystallinity and morphology of solution combustion synthesized Co3O4 as a catalyst precursor in hydrolysis of sodium borohydride

Solution combustion synthesized (SCS) cobalt oxide (Co3O4) powder has been studied as a catalyst precursor for the hydrolysis of sodium borohydride (NaBH4). Synthesis is completed in less than two minutes and results indicate SCS is capable of reproducibly synthesizing 98.5-99.5% pure Co3O4 nano-foam materials. SCS materials demonstrate an as-synthesized specific surface area of 24 m2 g−1, a crystallite size of 15.5 nm, and fine surface structures on the order of 4 nm. Despite having similar initial surface areas and sample purities, SCS-Co3O4 outperforms commercially available Co3O4 and elemental cobalt (Co) nano powders when used as a catalyst precursor for NaBH4 hydrolysis. Hydrogen generation rates (HGR) using 0.6 wt% NaBH4 in aqueous solution at 20 °C were observed to be 1.24 ± 0.2 L min−1 gcat−1 for SCS nano-foam Co3O4 compared to 0.90 ± 0.09 and 0.43 ± 0.04 L min−1 gcat−1 for commercially available Co3O4 and Co, respectively. The high catalytic activity of SCS-Co3O4 is attributed to its nano-foam morphology and crystallinity. During the hydrolysis of NaBH4, the SCS-Co3O4 converts in-situ to an amorphous active catalyst with a specific surface area of 92 m2 g−1 and exhibits a honeycomb type morphology.