Heterogeneous catalysis in solution. Part 18. The catalysis by carbons of oxidation–reduction reactions

A mechanism of electron-transfer-through-the solid is proposed to account for the widespread catalysis by carbons of redox reactions in solution. Charcoal catalysis of the aqueous reaction between Fe3+ and I– ions was predicted, found, and studied kinetically. The activation energy of the heterogeneous process was only 24 kJ mol–1 compared with 100 kJ mol–1 for the homogeneous reaction. The [Fe(CN)6]3–+ I– reaction in water was found to be catalysed by carbons as well as by several phthalocyanines. Neither reaction was catalysed by solids such as SiO2 or Ba[SO4] which do not conduct electronically.