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

Abstract

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)₆³⁻/Fe(CN)₆⁴⁻ 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.