The Electrochemical Properties And Modification Of LaFeO₃Nanopowder In Alkaline Solution

Perovskite-type oxide (ABO₃) have electrochemical reaction activity in alkalinesolution, its characteristics of low cost, easy activation and high discharge capacity(380-620mAh/g) make it may applied to high-energy Ni/MH batteries in the future.But the electrochemical reaction dynamics performance of the oxide is poor, and thereis still a lack of clear and systematic understanding of its electrochemical hydrogenstorage behavior and mechanism. Therefore, in order to improve dynamic performanceand have in-depth understanding of the electrochemical hydrogen storage behavior ofthe the ABO₃oxide materials, nano-crystalline powders LaFe₁-xM_xO₃(M=Co, Ni; x=0,0.2,0.4,0.6,0.8,1.0) and its coated samples were prepared by soft chemical methods.The materials testing methods of XRD, FT-IR, Uv-vis and TEM, and theelectrochemical testing techniques of charge-discharge, linear polarization andconstant potential step were employed to characterize the crystal structure, morphology,components, absorption properties and electrochemical performance of samples.Moreover, the electrochemical behavior before and after UV excitation ofLaFe₁-xNi_xO₃electrodes were studied. The research results are listed as follows.The LaFeO₃remains the orthorhombic perovskite structure and its dischargecapacity rised obviously after coating CeO₂or Pd. With the content(0%³%) of CeO₂or Pd increasing, the discharge capacity increased at first then decreased, it reached themaximum when the content of CeO₂was2%(258mAh·g-1) or the content of Pd was1%(306mAh·g-1). The electro-catalytic activity of LaFeO3electrode was wellimproved with the coating of CeO₂or Pd.As the substitute amount of Co increasing, the main structure of LaFe₁-xCo_xO₃(x=0-1.0) powders changed from orthorhombic to rhombohedral, the molecular volumedecreased, the grain size increased. Electrochemical studies have shown that, withincreasing of x, the discharge capacity of LaFe₁-xCo_xO₃electrodes increased first andthen decreased, the electrical conductivity increased, the Ioand D decreased. When x=0.4, the best electrochemical performance of the the LaFe₁-xCo_xO₃electrodes wereobtained, its discharge capacity reaches the maximum (356.7mAh·g-1).As the Ni substitute amount x increasing, the phase structures of LaFe₁-xNi_xO₃transform from orthorhombic to rhombohedral type, the both molecular volumes andthe grain sizes decreased. Electrochemical experimental results show that, with increasing x of Ni doping, the discharge capacity of LaFe₁-xNi_xO₃electrodes increasedgradually before the UV excitation, while the discharge capacity and Iosignificantlyenhanced under visible light irradiation. After the UV excitation, the largest dischargecapacities could be up to483.1mAh·g-1and the Ioincreased by a wide margin from3.54¹1.58(mA·g^-1) to8.37⁴0.11(mA·g^-1).