Simultaneous formation of Prussian Blue and copper hexacyanoferrate from a solution of Cu2+ and K3[Fe(CN)6] in presence of HAuCl4

• Electrosynthesis of CuHCF from solution of Cu2+, [Fe(CN)6]3− and HAuCl4 was studied.
• Simultaneous deposition of PB and CuHCF from solution of Cu2+, [Fe(CN)6]3− and HAuCl4.
• Cyclic voltammogram of deposited film shows pairs of redox peaks of PB and CuHCF.
• UV–Visible spectrum of deposited film shows absorption band of PB with λmax ∼ 700 nm.

An investigation predominantly by electrochemical techniques is conducted on copper hexacyanoferrate (CuHCF) film deposition on glassy carbon (GC) electrode from a solution of Cu2+ and [Fe(CN)6]3− ions in presence of HAuCl4. We observed that the potentiodynamic electrosynthesis of CuHCF from KNO3 solution containing Cu2+ and [Fe(CN)6]3− ions resulted in the co-deposition of Prussian Blue (PB), if HAuCl4 was present in the solution. The observations were supported by electrochemical techniques and UV–Visible spectroscopy. Recently, Yu et al. (J. Electroanal. Chem., 2010) reported potentiodynamic electrosynthesis of compact and uniform CuHCF nanoparticles on GC electrode under the synergic action of EDTA and HAuCl4 from a solution containing Cu2+, K3[Fe(CN)6], EDTA and HAuCl4 by cycling the electrode potential between 0.9 V and −0.2 V. HAuCl4 was used to improve the deposition of CuHCF on the electrode surface. However, Yu et al. did not report the formation of PB during the potential cycling on GC electrode in a supporting electrolyte solution containing Cu2+, K3[Fe(CN)6], EDTA and HAuCl4. Therefore, the present investigation is of more interest and importance as the potentiodynamic electrosynthesis of PB on GC electrode was reported from an acidic solution of K3[Fe(CN)6] in presence of HAuCl4 by cycling the potential between 0.0 V and 1.0 V (Senthil Kumar et al. Chem. Mater., 2007). These finding demonstrated that it is not possible to electrosynthesise a “pure” CuHCF by potentiodynamic method from a solution of Cu2+, [Fe(CN)6]3− and AuCl4- ions, because PB is deposited during the synthesis.