Mn3o4

Synthesis of mixed manganese-ruthenium oxides was based on the hydrothermal route of DeGuzman et al. who prepared manganese oxides, 20 but with the addition of KRuO 4 as oxidant, as well as KMnO 4 , to oxidise Mn 2+ . A solution of 0.2945 g (0.001864 moles) KMnO 4 in 5 mL of water, was added to a solution of 0.44 g (0.0026 moles) MnSO 4 •H 2 O in 1.5 mL of water and 0.7112 g concentrated H 2 SO 4 was added to give a final concentration of 1 mol dm -3 H 2 SO 4 . Varying amounts of KRuO 4 were substituted for the KMnO 4 (as described in the Results and Discussion section). The mixtures were then heated in 20 ml Teflon-lined Parr autoclaves, at a temperature of either 100 °C or 200 °C, for 24 hours. The solid products were recovered by centrifuge, washed with deionised water and dried at 80 °C in air. All chemicals were used as provided by Sigma-Aldrich. For the XANES spectroscopy experiments, the reference materials Mn(NO 3 ) 2 , Mn 2 O 3 , Mn 3 O 4 , MnO 2 , Ru(acac) 3 were also purchased from Sigma-Aldrich at the highest available purity and their identity confirmed using powder XRD, while the material La 4.87 Ru 2 O 12 was synthesised as in our previous work. 19a