Co-αAl2O3-Cu as shaped catalyst in NaBH4 hydrolysis

A study about catalytic films of Co-supported-over-alpha Al2O3 fabricated by electrophoretic deposition (EPD) is reported, the as-prepared shaped catalysts being intended to catalyze NaBH4 hydrolysis. Co-alpha Al2O3 supported over Cu substrate can be prepared by a 2-step route: (i) preparation of the supported catalyst Co-alpha Al2O3 (in powder form) by wet impregnation of CoCl2 over alpha Al2O3, followed by a reduction, and (ii) fabrication of Co-alpha Al2O3-Cu (thin film over Cu) by EPD. Both types of catalysts, whatever their form, are highly efficient in hydrolyzing NaBH4, conversions of 100% and HGRs of tens of mL(H-2) min(-1) being achieved at 60-80 degrees C. The Co-alpha Al2O3-Cu catalysts are even more reactive than the Co-alpha Al2O3 catalysts because the surface of the former materials becomes much more acid than that of the latter ones in the course of the EPD process. The respective rate laws and reaction kinetics have been determined. Independently on the catalyst form, apparent activation energies of about 52 kJ mol(-1) and positive reaction orders versus the initial NaBH4 concentration (i.e. 0.3-0.7) were calculated, suggesting that the EPD does not affect the reaction mechanisms. Besides, it is showed that the hydrolysis is really catalytic as well as typical of a heterogeneous process. For example, an apparent reaction order versus the Co content of 0.9 was calculated. All of these results among others are reported and discussed in the present article. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.