In Situ FT-IR/ATR Spectroelectrochemistry of Prussian Blue in the Solid State

Interfacial oxidation and reduction of Prussian Blue (PB), KFe[Fe(CN)6]‚nH2O (n ≈ 10), powder were probed in situ with Fourier transform infrared attenuated total reflection (FT-IR/ATR) spectroscopy. The combination of electrochemistry in the absence of liquid electrolyte with internal reflectance FT-IR spectroscopy was accomplished using a simple two-electrode sandwich-type cell in which a crystalline germanium served both as a working electrode and an infrared transparent element. Application of sufficiently large potential differences to sandwich electrodes led to oxidation and reduction of PB at opposing interfaces. The spectra, which were monitored by difference, clearly show changes in the cyanide stretching frequency range upon oxidation and reduction.