Higher‐order derivative spectroelectrochemical measurement of ferrocene dissolved into water‐in‐salt electrolyte solution

Ferrocene was dissolved in a water‐in‐salt solution containing a high concentration of a supporting electrolyte. Open‐circuit potential, electronic absorption spectra, and cyclic voltammetry revealed that a part of the dissolved ferrocene existed as ferrocenium ions. Spectroelectrochemical measurements and higher‐order derivative spectra revealed that the water‐in‐salt electrolyte aqueous solution is an excellent medium for electrochemical and spectroscopic measurement of redox‐active species with water insolubility.