Electrosynthesis of Ni/Al and Mg/Al Layered Double Hydroxides on Pt and FeCrAlloy supports: Study and control of the pH near the electrode surface

摘要

The coating of substrate materials with different geometry (gauze, plate, foam) and composition (Pt and FeCrAlloy) with Layered Double Hydroxides (Ni/Al, Mg/Al) was performed using the base electrogeneration method. The pH established by the cathodic reduction of nitrates in the proximity of a Pt gauze was measured with a glass electrode. In order to study the morphology, composition, and structure of the electrodeposited solids, at first Pt plates were used as substrates; the characterization was performed by SEM/EDS and XRD. Lastly, the study was focused on the FeCrAlloy foam more complex substrate. The more negative the applied potential was, the higher the pH values measured were; however, very negative potentials (-1.1 to -1.3 V vs SCE) promoted the formation of H_2 bubbles. Optimum potential for precipitating Layered Double Hydroxides depended on their chemical composition and even if the potential applied was adequate for the formation of pure phases, SEM/EDS analyses revealed that a sequential precipitation occurred at long synthesis times.