Hydrogen production using aluminum-water splitting: A combined experimental and theoretical approach

Hydrogen generation from aluminum hydrolysis with NaOH as an activator is investigated experimentally. A theoretical model is developed using the Density Functional Theory (DFT) and a one-dimensional transport model formalism. The effects of NaOH concentration and reaction temperature on hydrogen production rates are investigated. The kinetic parameters calculated by DFT are used in the COMSOL transport equations and compared. A transport model is implemented for a reaction-diffusion problem of water over the Al surface. The activation barrier increases as the reaction progresses and adsorption of H2O molecules is limited due to space constraints. The reaction rate constants depend on temperature, species convection, and vibrational frequency. The three chemical reaction steps have activation barriers ranging from 7.72 to 61.75 kJ/mol. The activation barrier of the first H2O dissociation step is Ea,1 = 7.72 kJ/mol, whereas the second and third steps have activation barriers of Ea,2 = 15.44 kJ/mol and Ea,3 = 61.75 kJ/mol, respectively. The estimated DFT harmonic vibrational frequency of H2O stretching mode is 3788 cm−1.