Hydrogen sulfide detection by poly(methylene blue) modified highly oriented pyrolytic graphite electrode

The electropolymerization of phenothiazine derivative, methylene blue (MB), on the surface of a basal plane highly oriented pyrolytic graphite (HOPG) was studied. Highly oriented pyrolytic graphite electrodes modified with the polymeric methylene blue (HOPG/pMB) was prepared by potential cycling in aqueous electrolyte solution containing a dissolved monomeric form of MB. The electrocatalytic activity of the electrode toward hydrogen sulfide was examined. In the presence of hydrogen sulfide, a new oxidation peak at potential about +0.340 V (vs. SCE) has arisen. No current signals corresponding to the hydrogen sulfide oxidation are observed in the absence of pMB on the electrode surface.