Co/S co-doped Mn3O4-based sulfur-oxide nano-flakes catalyst for highly efficient catalytic reduction of organics and hexavalent chromium pollutants

Abstract

Co/S co-doped Mn3O4 bimetal sulfur-oxide nano-flakes catalyst, Co/S-Mn3O4 or MnCoOS, with excellent catalytic reducing performance, was successfully prepared via a feasible method and characterized by different testing techniques. The existence of heterovalent Co2+/Co3+ and Mn2+/Mn3+ states in Co/S-Mn3O4 enhances the electron lifetime and facilitates fast electron transfer, which speeds up the chemical pollutant reduction reaction. Likewise, the valence transition between Co2+/Co3+ and Mn2+/Mn3+ makes the Co/S co-doped in Mn3O4 catalyst increase its electrochemically active surface sites. The MnCoOS catalyst labeled as MnCoOS-3 exhibits good long-term stability and electrochemical performance. The Co/S-Mn3O4 catalytic performance was also tested for the reduction of 4-nitrophenol (4-NP), methyl orange (MO), rhodamine (RhB), methylene blue (MB), and hexavalent chromium Cr(VI). The results exhibited that the MnCoOS-3 catalyst prepared with n(Mn):n(Co):n(C2H5NS) = 1:1:1 had the best catalytic activity, with 10 mg it ultimately reduced 100 ml of 10 ppm 4-NP, 20 ppm MO, RhB, and MB, and 50 ppm Cr(VI) within 12, 10, 10, 20, and 24 min, respectively. Therefore, Co/S co-doped Mn3O4 catalysts have excellent catalytic potential application merits in reducing chemical pollutants.