An insight into the electrochemical behavior of Co/Al layered double hydroxide thin films prepared by electrodeposition

A detailed study aimed at clarifying the electrochemical behavior of Co/Al-LDH thin films, prepared on Pt electrode by electrodeposition at −0.9 V, has been carried out. Reproducible thin and homogeneous films with variable amounts of LDH coated on the electrode surface have been achieved by varying the electrodeposition time (t = 5, 10, 30 and 60 s): 29.2 ± 0.7, 37.9 ± 1.4, 55.1 ± 2.1 and 62.5 ± 4.3 μg cm−2, respectively. X-ray diffraction, spectroscopic techniques and the electrochemical quartz crystal microbalance analysis have been used to give an insight into the phase changes occurring when the as-prepared Co/Al-LDH thin films were oxidized and reduced by cycling the potential between 0 and 0.6 V/SCE in 0.1 M KOH. Our experiments demonstrate that the irreversible oxidation peak observed in the first cycle corresponds to the transformation of the Co(II)/Al-LDH phase in a γ-Co(III)OOH like phase. This resulting phase is stable under cycling and shows a pseudo-capacitive behavior with an estimated specific capacitance of 500 F g−1.

► Co layered double hydroxide thin films are prepared by electrodeposition. ► Electrochemical oxidation in alkaline solution lead to an irreversible phase transition. ► The resulting γ-Co(III)OOH like phase is highly stable under cycling. ► It shows a pseudo-capacitive behavior with a specific capacitance of 500 F g−1.