Fe(CN)63−/Fe(CN)64− redox in the interlayer determined by the charge density of ZnnCr-layered double hydroxides

Redox of Fe(CN)63− and Fe(CN)64− in the ZnCr layered double hydroxide interlayer has been investigated. The conversion from Fe(CN)63− to Fe(CN)64− or from Fe(CN)64− to Fe(CN)63− in the ZnCr-LDH interlayer has been confirmed, depending on the Zn:Cr molar ratio. Both Fe(CN)63− and Fe(CN)64− are observed in all samples no matter whether the initial anion is Fe(CN)63− or Fe(CN)64− before precipitation. Deconvolution of the FTIR band around 2100 cm−1 reveals that the relative amount of Fe(CN)64− and Fe(CN)63− in the LDH interlayer is considerably dependent on the Zn:Cr molar ratio. In brief, Fe(CN)64− is preferred at the ratio of 2:1 while there is more Fe(CN)63− in the ratio of 4:1. Therefore, it is our hypothesis that the charge density of the hydroxide layer is a key factor that directs the redox of Fe(CN)63−/Fe(CN)64−. The possible redox processes have also been proposed.