No abstract

We describe the simple preparation of octahedral Mn 3 O 4 nanomaterials with a typical diameter around 300-400 nm using a one step dealloying of MnAl alloy at room temperature. The as-made sample exhibits high performance as an anode material for Li-ion batteries. Electrochemical measurements reveal that the Mn 3 O 4 octahedra have an ultralong cycle life with capacity retentions of 81.3% and 77.8% after 500 cycles at 100 and 300 mA g À1 , respectively. Moreover, the Mn 3 O 4 octahedra deliver a stable capacity at a high rate of 1000 mA g À1 with a good rate capability. The as-made Mn 3 O 4 octahedra exhibit great potential for application as anode materials for Li-ion batteries with the advantages of unique performance and easy preparation.

Synthetically tuning the surface properties of many oxide catalysts to optimize their catalytic activity has been appreciably challenging given their complex crystal structure.Nickelate oxides (e.g., La2NiO4+δ) are among complex, layered oxides with great potential toward efficiently catalyzing chemical/electrochemical reactions involving oxygen (oxygen reduction, ammonia oxidation). Our theoretical calculations show that the surface structure of La2NiO4+δ plays a critical role in its activity, with (001)-Ni oxide terminated surface being the most active. This is demonstrated through the effect on the energetics associated with surface oxygen exchange -key process in reactions involving oxygen on these oxides. Using a reverse microemulsion method, we have synthesized La2NiO4+δ nanorod-structured catalysts highly populated by (001)-Ni oxide terminated surfaces. We show that these nanostructures exhibit superior catalytic activity toward oxygen exchange/reduction as compared to the traditional catalysts, while maintaining stability under reaction conditions. The findings reported here pave the way for engineering complex metal oxides with optimal activity.

A nanoporous PdNi (NP-PdNi) alloy with uniform structure dimension is easily fabricated by one-step mild dealloying of a PdNiAl precursor alloy. NP-PdNi consists of an interconnected nanoscaled network backbone and bicontinuous hollow channels in all three dimensions with a typical ligament size of around 5 nm. Electrochemical measurements indicated that the NP-PdNi alloy has superior electrocatalytic activity towards oxygen reduction reaction (ORR) with much higher specific and mass activities as well as higher methanol tolerance compared with Pt/C catalysts. Importantly, NP-PdNi suffers less loss of the ORR activity and the electrochemical surface area of metal upon 5000 potential cycles in acid solution than Pt/C, indicating a better catalytic durability. The NP-PdNi alloy holds great application potential as a cathode electrocatalyst in the fuel cell related technology with unique ORR performance, high structure stability, and easy preparation.