Hydrolysis of Al for hydrogen production: A joint experimental and first-principles density functional theory investigation

Efficient and environmentally friendly H₂ production is one of the most pressing challenges that face modern energy science. Hydrolysis of water over metals is used as an affordable and sustainable method for H₂ production. Due to its abundance, low cost, and low toxicity, aluminum (Al) is a promising candidate material to be used for water dissociation. In this work, we investigate using impedance measurements, XRD, SEM, and hydrogen volume measurement methods, the H₂ evolution reactions from Al wires and Al powder in a NaOH solution. The experimental results are interpreted with the help of first-principles density functional theory (DFT) calculations. Our results shed light on several important aspects of the reaction's mechanism, such as the removal of the native oxide and the evolution of the surface morphology. We computationally design a six-step reaction mechanism that describes the erosion of the surface and release of Al(OH)₄ ⁻. Our results indicate that the reaction proceeds with low activation barriers at the initial stages, but these barriers increase as more H₂O molecules adsorb and dissociate on the surface. We observe that factors controlling the rate-determining step, and the computed activation barrier, compare well with the experimentally derived values.