Nano-sized Mn oxides on halloysite or high surface area montmorillonite as efficient catalysts for water oxidation with cerium(iv) ammonium nitrate: support from natural sources.

We used halloysite, a nano-sized natural mineral, and high surface area montmorillonite as supports for nano-sized Mn oxides to synthesize efficient water-oxidising catalysts. The composites were synthesized by an easy and simple procedure, and characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction spectrometry. Halloysite has low amounts of hydroxyl groups on its surface, thus it causes better dispersion of Mn oxides. The water-oxidising activities of these composites were also measured in the presence of cerium(iv) ammonium nitrate. Considering the low-cost, environmentally friendly precursors, simple synthesis and efficiency for water oxidation, the composites are promising catalysts in artificial photosynthetic systems.