Effect of metal nitrate concentration on the electrodeposition of hydrotalcite-like compounds on open-cell foams

Mg/Al hydrotalcite-like compounds were deposited on FeCrAlloy open-cell metal foams by the electro-base generation method in metal nitrate baths of different concentration (0.03, 0.06 and 0.10 M, Mg/Al = 3/1). The modifications of both electrochemical and chemical processes by the electrolyte concentration were investigated. For comparison purposes, experiments were carried out in KNO3 solutions and using FeCrAlloy plates as working electrodes. The reduction processes followed a surface reduction behaviour and were slowed down by the solid deposition or the ineffective solution replenishment at the electrode interface, being more remarkable with more concentrated baths. Hydrotalcite-like, brucite and probably gibbsite phases were deposited at − 1.2 V vs SCE for 100–2000 s. The metal nitrate concentration determined both OH− production by nitrate reduction and OH− consumption by precipitation of cations, these processes not only governed the amount of solid deposited and its distribution on the support but also the solid growth mechanism, crystallinity of the phases and intercalating anions inside the hydrotalcite.