Improvement of the capacitive performances for Co-Al layered double hydroxide by adding hexacyanoferrate into the electrolyte.

This paper reports on the improvement on the capacitive properties of Co-Al layered double hydroxide (Co-Al LDH) by adding hexacyanoferrate(II) and (III) solely or jointly into 1 M KOH aqueous solution. Owing to the high reversibility, the Fe(CN)(6)(3-)/Fe(CN)(6)(4-) ion pair acts as an electron relay at the electrode/electrolyte interface during charge and discharge by coupling in the redox transition of Co(II)/Co(III) in the Co-Al LDH electrode. Electrochemical impedance spectra and Tafel curves provide direct evidences with decreased charge-transfer resistance and increased exchange current density in the alkaline solution containing hexacyanoferrate ions, respectively.