Kinetics study on hydrolytic dehydrogenation of alkaline sodium borohydride catalyzed by Mo-modified Co-B nanoparticles

Mo-modified Co-B nanoparticles have been prepared by the co-deposition chemical reduction method. The relationship between microstructure, catalytic activity and kinetics performance for H-2 generation by hydrolysis of alkaline NaBH4 is studied. Compared to unmodified Co-B nanoparticles, the synthesized Co-Mo-B nanoparticles exhibit smaller particle size with average diameter of 30 nm, more uniform distribution with unconspicuous agglomeration, and larger specific surface area. The induced Mo in the Co-Mo-B catalyst exists as molybdenum oxides, which facilitates the dissociation of water due to weakening of the bond strength of the H-OH bond and promote the hydrolysis reaction of NaBH4. As a result, the maximum hydrogen generation rate and the activation energy of the hydrolysis reaction catalyzed by Mo-modified Co-B catalyst reach to 4200 mL(H2) min(-1) g(catalyst)(-1)and 43.7 kJ mol(-1), respectively, which are superior to those of the Co-B catalyst. Kinetic studies show that, in low concentration of NaBH4, first-order reaction is observed with respect to NaBH4 concentration, indicating that surface adsorption of BH4- is the rate-limiting step. At high NaBH4 concentration, hydrolysis reaction is zero-order, and the hydrolysis rate depends on surface reaction of adsorbed molecules. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.