Sodium Cobalt Metaphosphate as an Efficient Oxygen Evolution Reaction Catalyst in Alkaline Solution

Sodium cobalt metaphosphate [NaCo(PO₃)₃] has CoO octahedra (CoO₆) and shows superior oxygen evolution reaction (OER) activity in alkaline solution, comparable with the state‐of‐the‐art precious‐metal RuO₂ catalyst. OER catalysts of this metaphosphate are prepared by combustion (Cb) and solid‐state (SS) methods. The combustion‐assisted method offers a facile synthesis and one‐step carbon composite formation. Unusually high catalytic activity was observed in NCoM‐Cb‐Ar and could be due to chemical coupling effects between NaCo(PO₃)₃ and partially graphitized carbon. This novel electrocatalyst exhibits very small overpotential of 340 mV with high mass activity of 532 A g^?1. Good charge transfer abilities and chemical coupling between NaCo(PO₃)₃ and amorphous carbon gives the OER activity in NCoM‐Cb‐Ar.     

Porous,hollow Li<Subscript>1.2</Subscript>Mn<Subscript>0.53</Subscript>Ni<Subscript>0.13</Subscript>Co<Subscript>0.13</Subscript>O<Subscript>2</Subscript> microspheres as a positive electrode material for Li-ion batteries

A porous, hollow, microspherical composite of Li₂MnO₃ and LiMn_1/3Co_1/3Ni_1/3O₂ (composition: Li_1.2Mn_0.53Ni_0.13Co_0.13O₂) was prepared using hollow MnO₂ as the sacrificial template. The resulting composite was found to be mesoporous; its pores were about 20 nm in diameter. It also delivered a reversible discharge capacity value of 220 mAh g^?1 at a specific current of 25 mA g^?1 with excellent cycling stability and a high rate capability. A discharge capacity of 100 mAh g^?1 was obtained for this composite at a specific current of 1000 mA g^?1. The high rate capability of this hollow microspherical composite can be attributed to its porous nature.

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Ultra-rapid combustion synthesis of Na<Subscript>2</Subscript>FePO<Subscript>4</Subscript>F fluorophosphate host for Li-ion and Na-ion insertion

Exploring soft-chemistry synthesis of Fe-based battery cathode materials, we have optimized combustion synthesis as an ultra-rapid approach to produce Na₂FePO₄F fluorophosphate cathode. It yields nanoscale, carbon-coated target product by annealing (at 600 °C) for just 1 min. The purity of the material crystallizing in the orthorhombic structure was confirmed by powder X-ray diffraction pattern and XPS analysis, while the morphology was studied by scanning electron microscopy. The as-synthesized material exhibits good electrochemical performance delivering a first discharge capacity of more than 70 mAh/g at C/10 rate versus both Li⁺/Li and Na⁺/Na, hence acting as an efficient host for both Li-ion and Na-ion insertion. Combustion synthesis can be employed as an economic route for synthesis and rapid screening of various phosphate-based insertion materials.     

Aqueous spray-drying synthesis of alluaudite Na2+2xFe2−x(SO4)3 sodium insertion material: studies of electrochemical activity,thermodynamic stability,and humidity-induced phase transition

Journal of Solid State Electrochemistry - In pursuit of high-energy density sodium insertion materials, polyanionic frameworks can be designed with tuneable high-voltage operation stemming from...