Photocatalytic Production of Hydrogen Peroxide by Tris(2,2‘-bipyridine) Ruthenium(II) Using Humic Acids as Electron Donor

The photosensitized production of H2O2 by tris(2,2‘-bipyridine) ruthenium(II) complex [Ru(bpy)32+] was enhanced ∼120-fold by the presence of humic acid (HA). It was found that methyl viologen (MV2+) as a redox mediator in this system was required to produce H2O2. Moreover, in the present system, H2O2 was not produced in the absence of formic acid. The presumed role of formic acid is to reduce the oxidized HA. The reducing ability of HA assisted the photocatalytic reaction of Ru(bpy)32+. In addition, the results of the effect of inorganic salt on H2O2 production suggest that the binding abilities of Ru(bpy)32+ and MV2+ with HA are determinant in the enhancement of H2O2 production.