Effect of copper (II) chloride as an activator on reducing the incubation time in hydrogen generation from the reaction of aluminum with water
摘要
Hydrogen generation through the reaction of aluminum with water offers a promising pathway for clean energy production. However, the formation of a passive oxide layer on aluminum particles significantly delays hydrogen evolution by extending the incubation period before reaction initiation. In this study, to decrease this incubation time, the effect of copper (II) chloride (CuCl2) as a chemical activator was investigated. Experimental tests were conducted at two isothermal temperatures, 35 °C and 45 °C, with and without the addition of 0.2 g CuCl2 (20 wt% relative to Al). Without CuCl2, the incubation times were recorded as 3000 min at 35 °C and 160 min at 45 °C. Upon addition of CuCl2, incubation times were drastically reduced to 40 min at 35 °C and 25 min at 45 °C. Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), and X-Ray Diffraction (XRD) analyses were employed to characterize the aluminum surfaces. SEM and EDS analyses confirmed the formation of cracks in the protective oxide layer and deposition of metallic copper on aluminum surfaces, supporting the proposed galvanic replacement mechanism. The significant decrease in incubation time arises from the galvanic displacement reaction between Al atoms and Cu2+ ions, driven by the difference in standard reduction potentials. Aluminum donates electrons and oxidizes to Al3+, while Cu2+ ions are reduced and precipitate as metallic copper on the aluminum surface. The heterogeneous deposition of copper induces localized stresses, structural instability, and microcrack formation within the passive alumina layer, allowing water to penetrate to the aluminum core earlier. These results demonstrate that CuCl2 can serve as an efficient, low-cost, and easily applicable activator to significantly accelerate hydrogen generation from aluminum–water reactions, especially at low temperatures.