Effect of the Synthesis Route and Fe Presence on the Redox Activity of Ni in Layered Double Hydroxides

Pt electrodes coated with a Ni/Al or Ni/Fe layered double hydroxide (LDH) were studied to investigate whether the presence of Fe and the extent of crystallinity affect the performance of the Ni centers as redox mediators for oxidizable compounds. The LDHs were synthesized by both a chemical and an electrochemical method, which allowed the obtainment of thin and well-adherent LDH films having similar morphology but a different crystallinity degree. Fe centers were not electroactive but they influenced the electroactivity of Ni, shifting the redox potential to less anodic values and increasing the percentage of the electroactive Ni sites. The LDHs prepared by electrodeposition were more conductive than the chemically synthesized LDHs, and, when Fe was the trivalent metal, the electronic conductivity was further increased. The highest electrocatalytic efficiency, evaluated taking glucose as model compound, was obtained for the electrodes coated with the electrochemically synthesized LDHs.