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

The coating of substrate materials with different geometry (gauze, plate, foam) and composition (Pt andFeCrAlloy) with Layered Double Hydroxides (Ni/Al, Mg/Al) was performed using the base electrogenera-tion method. The pH established by the cathodic reduction of nitrates in the proximity of a Pt gauze wasmeasured with a glass electrode. In order to study the morphology, composition, and structure of theelectrodeposited solids, at first Pt plates were used as substrates; the characterization was performedby SEM/EDS and XRD. Lastly, the study was focused on the FeCrAlloy foam more complex substrate. Themore negative the applied potential was, the higher the pH values measured were; however, very neg-ative potentials (−1.1 to −1.3 V vs SCE) promoted the formation of H2bubbles. Optimum potential forprecipitating Layered Double Hydroxides depended on their chemical composition and even if the poten-tial applied was adequate for the formation of pure phases, SEM/EDS analyses revealed that a sequentialprecipitation occurred at long synthesis times.