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FeF 3 /C nanocomposites, where FeF 3 nanocrystals had been dispersed into a porous carbon matrix, were successfully fabricated by a novel vapour-solid method in a tailored autoclave. Phase evolution of the reaction between the precursor and HF solution vapour under air and argon gas atmospheres were investigated. The results showed that the air in the autoclave played an important role in driving the reaction to form FeF 3 . The as-prepared FeF 3 /C delivered 134.3, 103.2 and 71.0 mA h g À1 of charge capacity at a current density of 104, 520, and 1040 mA g À1 in turn, exhibiting superior rate capability to the bare FeF 3 . Moreover, it displayed stable cycling performance, with a charge capacity of 196.3 mA h g À1 at 20.8 mA g À1 . EIS and BET investigations indicated that the good electrochemical performance can be attributed to the good electrical conductivity and high specific surface area that result from the porous carbon matrix.

In this work, a novel electrocatalyst, Mn 0.3 Ce 0.7 O 2 , with relatively high power performance has been, for the first time, proposed for metal/air batteries. The as-prepared samples are well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma (ICP) and nitrogen sorption experiments. Meanwhile, electrocatalytic activity towards the reduction of oxygen of Mn 0.3 Ce 0.7 O 2 is compared with those of the pure MnO 2 and CeO 2 . It is observed that the Mn 0.3 Ce 0.7 O 2 solid solution is well formed after the calcination. Electrochemical results show that Mn 0.3 Ce 0.7 O 2 exhibits much higher electrocatalytic activity in the oxygen reduction reaction (ORR) than pure MnO 2 under high discharge current density, which is probably attributed to the effective activation of molecular oxygen over the Mn 0.3 Ce 0.7 O 2 solid solution and higher surface area.

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