In situ generation of hydrogen from water by aluminum corrosion in solutions of sodium aluminate

A new process to obtain hydrogen from water using aluminum in sodium aluminate solutions is described and compared with results obtained in aqueous sodium hydroxide. This process consumes only water and aluminum, which are raw materials much cheaper than other compounds used for in situ hydrogen generation, such as hydrocarbons and chemical hydrides, respectively. As a consequence, our process could be an economically feasible alternative for hydrogen to supply fuel cells. Results showed an improvement of the maximum rates and yields of hydrogen production when NaAlO2 was used instead of NaOH in aqueous solutions. Yields of 100% have been reached using NaAlO2 concentrations higher than 0.65 M and first order kinetics at concentrations below 0.75 M has been confirmed. Two different heterogeneous kinetic models are verified for NaAlO2 aqueous solutions. The activation energy (E-a) of the process with NaAlO2 is 71 kJ mol(-1), confirming a control by a chemical step. A mechanism unifying the behavior of Al corrosion in NaOH and NaAlO2 solutions is presented. The application of this process could reduce costs in power sources based on fuel cells that nowadays use hydrides as raw material for hydrogen production. (C) 2008 Elsevier B.V. All rights reserved.