The coralline cobalt oxides compound of multiple valence states deriving from flower-like layered double hydroxide for efficient hydrogen generation from hydrolysis of NaBH4

Abstract

Efficient hydrogen storage, transportation and generation are key-technology for future hydrogen economy. Sodium borohydride (NaBH4) stands out as promising hydrogen energy carrier with merits of high volumetric density and environmentally benign hydrolysis products. Flower-like layered double hydroxide α-Co(OH)2 with intercalation of B species was synthesized via hydrothermal crystallization method using sodium tetraphenylboron as source of B and alkaline, which makes it different from the previous supporting materials. Pure or mixed cobalt oxides with different valence states containing B (CoO/B, Co3O4/B, Co+CoO/B, CoO+Co3O4/B) were subtly prepared via controlling calcination temperature, time and atmosphere for sodium borohydride hydrolysis. Coral-like CoO+Co3O4/B displayed superior hydrogen generation rate (6478 mlH2·min−1·g−1metal) with arrhenius activation energies of 41.14 kJ/mol for NaBH4 hydrolysis in alkaline solutions compared to those reported pure precious metals. The out-standing catalytic performance of CoO+Co3O4/B may be attributed to electron transfer among cobalt oxide. DFT calculation indicates NaBH4 hydrolysis undergoes a reaction path on CoO+Co3O4 surface with lower relative energies.