Electrodeposition of Prussian Blue/Carbon Nanotubes Composites at a Liquid-Liquid Interface

The interface between two immiscible liquids has long being used for the study of interfacial ion and electron transfer reactions or for the synthesis and assembly of materials. In this work, Prussian blue (PB -Fe4[Fe(CN)6]3) was electrodeposited over a free-standing carbon nanotube (CNT) film assembled at a liquid-liquid (L/L) interface formed between water and 1,2-dichlorobenzene (Figure 1). With a four-electrode cell, the interface polarization was performed through both cyclic voltammetry and chronoamperometry. PB was formed by heterogeneous reaction using species in aqueous phase and iron from CNTs cavities, generating a stable CNT/PB composite. Aqueous phase of K3[Fe(CN)6] showed to be unstable under applied conditions, decomposing during PB synthesis. However, K4[Fe(CN)6] presented a more stable behavior thus suitable for composite preparation. The modification of the interface through electrodeposition was monitored by in situ Raman spectroelectrochemsitry. PB formation was confirmed by a shift and an increase of CN stretching modes due to iron coordination to nitrogen and arise of resonant Raman effect, as well as changes in CNT bands due modification of their walls by PB deposition and a p-doping due components interaction. The obtained CNT/PB composite formed at the biphasic system was stable and electrochemically active at the L/L interface, making it suitable for applications not only after transfer to a desired substrate but also in situ at the L/L interface itself.