Atomic layer deposited cobalt oxide: An efficient catalyst for NaBH4 hydrolysis

Thin films of cobalt oxide are deposited by atomic layer deposition using dicobalt octacarbonyl [Co-2(CO)(8)] and ozone (O-3) at 50 degrees C on microscope glass substrates and polished Si(111) wafers. Self-saturated growth mechanism is verified by x-ray reflectivity measurements. As-deposited films consist of both the crystalline phases; CoO and Co3O4 that gets converted to pure cubic-Co3O4 phase upon annealing at 500 degrees C under ambient condition. Elemental composition and uniformity of the films is examined by x-ray photoelectron spectroscopy and secondary ion-mass spectroscopy. Both as-deposited and the annealed films have been successfully tested as a catalyst for hydrogen evolution from sodium borohydride hydrolysis. The activation energy of the hydrolysis reaction in the presence of the as-grown catalyst is found to be ca. 38 kJ mol(-1). Further implementation of multiwalled carbon nanotube, as a scaffold layer, improves the hydrogen generation rate by providing higher surface area of the deposited catalyst. (C) 2015 American Vacuum Society.