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Abstract: A system with a continuous reactor to produce hydrogen by sodium borohydride hydrolysis was designed and built. The purpose was to test a supported Co–B catalyst durability upon cycling and long life experiments in high conversion conditions. A Stainless Steel monolith was built and calcined to improve adherence. For comparison a Ru–B catalyst was tested upon cycling. Both Co–B and Ru–B catalysts are durable during 6 cycles and then deactivate. A known reactivation procedure has proven to be more effective for the Co–B than for the Ru–B catalyst. This is related to stronger adsorption of B–O based compounds on the Co–B catalyst which is reversible upon acid washing. For the Ru–B catalyst deactivation may be more related to particle agglomeration than to the adsorption of B–O based species. The continuous system enlarges the catalysts durability because of the continuous borate elimination at elevated temperatures. [Copyright &y& Elsevier]

Abstract: Catalyzed hydrolysis of sodium borohydride (SBH) is a promising method for the hydrogen supply of fuel cells. In this study a system for controlled production of hydrogen from aqueous sodium borohydride (SBH) solutions has been designed and built. This simple and low cost system operates under controlled addition of stabilized SBH solutions (fuel solutions) to a supported CoB catalyst. The system works at constant temperature delivering hydrogen at 1Lmin−1 constant rate to match a 60-W polymer electrolyte membrane fuel cell (PEMFC). For optimization of the system, several experimental conditions were changed and their effect was investigated. A simple model based only on thermodynamic considerations was proposed to optimize system parameters at constant temperature and hydrogen evolution rate. It was found that, for a given SBH concentration, the use of the adequate fuel addition rate can maximize the total conversion and therefore the gravimetric storage capacity. The hydrogen storage capacity was as high as 3.5wt% for 19wt% SBH solution at 90% fuel conversion and an operation temperature of 60°C. It has been demonstrated that these optimized values can also be achieved for a wide range of hydrogen generation rates. Studies on the durability of the catalyst showed that a regeneration step is needed to restore the catalytic activity before reusing. [Copyright &y& Elsevier]