Batch sodium borohydride hydrolysis systems: Effect of sudden valve opening on hydrogen generation rate

A study was undertaken in order to investigate the potential of hydrogen (H-2) generation by hydrolysis of sodium borohydride solution (10 wt% NaBH4 and 7 wt% NaOH), in batch reactors, operating at moderate pressures (up to similar to 1.2 MPa), in the presence of a powdered nickel-ruthenium based catalyst, reused between 311 and 316 times, to feed on-demand a proton exchange membrane fuel cell. A different approach to the testing of the performance of the batch NaBH4, hydrolysis system is explored, by the quick opening of the reactor release gas valve, to satisfy a sudden H-2 demand; and hydrogen generation rates (HGR) are evaluated by changing catalyst amount, operating pressure and successive refueling. The results have shown the tendency of the studied system to maintain constant the H-2 generation rates, before and after one swift interruption, for single fuel injections (for 2.1 wt% of reused Ni-Ru based catalyst, a maximum value of HGR of 0.61 L(H-2)min(-1) g (catalyst) at 0.4 MPa, or based on the active metal ruthenium, of 47.5 L(H-2)min(-1) g(-1)(Ru), was achieved). This trend was different in the experiments with successive refueling. The present paper go forward in testing the potential of NaBH4 system over reused Ni-Ru catalyst after supplying a sudden demand of H-2. Bearing in mind the market of low-power H-2-PEMFCs for portable devices, the herein results are original and useful from an application point of view. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.