Study on degradation of filamentary Ni catalyst on hydrolysis of sodium borohydride

Abstract

An investigation of durability characteristics of a pasted filamentary Ni catalyst was performed and extensive approaches for elucidating the degradation mechanism of the catalyst were undertaken. The H-2 generation rate of pasted filamentary Ni catalyst gradually decreases with cycling and 76% of the initial H-2 generation rate remains at 200 cycles. After 200 cycles, SEM images show an agglomeration of catalyst particles and a film on the pasted catalyst. An agglomeration of catalyst results in a reduction of specific surface area, as indicated by BET analysis, and a film on the pasted catalyst was formed by an accumulation of potassium originating from alkaline solution, and sodium and boron, which consists of Na2B4O7 (.) 10H(2)O, a potassium borate compound (KBxOy) and boron oxide (B2O3), as indicated by XRD and XPS analyses. Consequently, a deterioration of the catalyst upon hydrolysis of sodium borohydride results from agglomeration of the catalyst and the film formed on the catalyst. (C) 2004 Elsevier B.V. All rights reserved.