Electrochemical synthesis and photoelectrochemical characterization of copper hexacyanoferrate (II) deposited on n-Si(1 0 0)

• We examined the nucleation and growth mechanisms of K2Cu[Fe(CN)6] on silicon.
• The photoelectrochemical behaviour of silicon/Cu[Fe(CN)6] interface was studied.
• Light is required for observing the redox process on silicon/Cu[Fe(CN)6] interface.
• Thinner films of K2Cu[Fe(CN)6] present higher electrochemical reversibility.
• We obtained the diffusion coefficient for K+ ions in the K2Cu[Fe(CN)6] film.

In this study, we examined the synthesis and characterization of copper hexacyanoferrate (II) on an n-Si(1 0 0) substrate. The copper hexacyanoferrate (II) was formed in the following stages: (i) deposition of metallic copper on an n-Si(1 0 0) electrode using an electroless process and (ii) electrooxidation of the copper film in a solution containing Fe(CN)64− ions. In the first stage, a study using a potential step method was performed, and the corresponding nucleation and growth mechanisms were determined. A morphologic analysis of the deposits obtained at different potentials was performed using atomic force microscopy. The results were consistent with a 3D progressive nucleation with diffusion-controlled growth. Electrochemical characterization under illumination demonstrated a charge transfer process due to the photogenerated holes in the valence band of silicon. Afterwards, the diffusion coefficient of the potassium ions and rate constants of the electrochemical processes were determined. Finally, this research is designed to increase the understanding of this system for its possible use in an electrochemical storage device that can be loaded in situ via the photovoltaic action of the doped silicon.