Hydrogen production via corrosion of aluminum alloys: Influence of alloy composition, pH, and temperature

Abstract

With growing concerns over fossil fuel depletion and environmental pollution, the need for clean, renewable energy sources has never been more critical. Among the promising alternatives, hydrogen stands out as a high-energy, sustainable, and environmentally friendly fuel. In this context, the current study investigates a laboratory-scale method for producing hydrogen gas through the corrosion of three aluminum alloys (Al 2024, Al 6061, and Al 7075) in acidic (HCl) and alkaline (NaOH) solutions at varying concentrations and temperatures. The research employs hydrogen evolution (HE), weight loss (WL), and potentiodynamic polarization (PDP) techniques, alongside optical imaging, to analyze surface changes in the alloys under different experimental conditions. The results clearly demonstrated that hydrogen production increased significantly with increasing concentrations of both HCl and NaOH. However, it wasn’t just the alloy’s chemical composition driving this reaction-the internal structure played a crucial role. The type, distribution, and behavior of intermetallic compounds (IMCs) within each alloy had a major impact on hydrogen production. Among the tested alloys, Al 7075 produced the most hydrogen in acidic conditions (HCl), primarily due to the selective dissolution of Zn- and Mg-rich IMCs. In contrast, Al 2024 showed the highest hydrogen output in alkaline environments (NaOH), a result attributed to the catalytic influence of its Cu-rich phases. These differences highlight the importance of alloy microstructure in optimizing hydrogen generation efficiency. The PDP measurements further confirmed that the corrosion behavior of the alloys in both HCl and NaOH environments is governed by cathodic control, with the corrosion mechanism remaining consistent despite increasing solution concentrations. Additionally, elevated temperatures significantly boosted hydrogen production rates, facilitated by the alloys' relatively low apparent activation energies, which enhanced their susceptibility to corrosion and hydrogen release. The economic aspect of aluminum alloys was considered and correlated with their hydrogen generation efficiency.