Mn oxide/nanodiamond composite: A new water-oxidizing catalyst for water oxidation

Herein, we report nanosized Mn oxide/nanodiamond composites as water-oxidizing compounds. The composites were synthesized by easy and simple procedures by the reaction of Mn(ii) and MnO₄^- in the presence of ND (1), the reaction of MnO₄^- and ND at different temperatures (2 and 4) and by the simple mixing of Mn-Ca oxide and ND (3). The compounds were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectrometry, Fourier transform infrared spectroscopy and atomic absorption spectroscopy. The water-oxidizing activities of these compounds were also considered in the presence of cerium(iv) ammonium nitrate. A Mn oxide/nanodiamond resulting from the reaction of MnO₄^- and ND shows a turnover frequency of ∼1 (mmol O₂/mol Mn.s). However, other Mn oxide/nanodiamond composites show lower activity toward water oxidation.