Electrocatalytic reaction, catalytic autoxidation, and supported catalytic autoxidation of sulfur oxoanions by FeTSPP and Mn(4-TMPyP)

Abstract

The electrocatalysis of the sulfur oxoanions SO 3 2− and S 4O 6 2− by the catalyst FeTSPP were investigated in aqueous solution at room temperature. The water-soluble iron tetrakis(4-sulfonatophenyl) porphine (FeTSPP) uses an electrochemical process to oxidize Fe IIITSPP or the iron(III) dimer (TPPS)Fe IIIOFe III(TPPS) to the Fe III(TSPP ·+) species. FeTSPP can perform the electrocatalytic oxidation of sulfite to sulfate. FeTSPP shows two redox couples and can perform both electrocatalytic oxidation and reduction of sulfite when the pH is ca. 2.0, and the ratio of electrocatalytic reduction to electrocatalytic oxidation I pcat I Pd = 3 . FeTSPP can also perform the electrocatalytic reduction of S 4O 6 2− to S 2O 3 2− through the Fe ITSPP species. Mn(4-TMPyP) can perform the electrocatalytic oxidation of sulfite only through the Mn IV(4-TMPyP) species. NaSH can be electrocatalytically oxidized through both the Mn III(4-TMPyP) and Mn IV(4-TMPyP) species, but each reaction has different electrocatalytic efficiencies. Mn(4-TMPyP) acts as a catalyst in the autoxidation of SO 3 2− to sulfate in the presence of oxygen. Mn(4-TMPyP), supported on a zeolite molecular sieve, has been used effectively as a catalyst in the autoxidation of SO 3 2− to sulfate in the presence of oxygen at room temperature in an aqueous solution.