Kinetics Of NiSO₄-Co（NO₃）₂-Ammonium Hydroxide Reaction For The Preparation Of Ni-Co-O Composite

The Ni-Co-O composites, as a new electrode material of supercapacitors, have drawn much attention in recent years due to their advantages such as low costs, good electrochemical performance and environmental-friendly nature. Current scientific research of Ni-Co-O composite is mainly focused on the improvement of its electrochemical property and synthesis method. However, there is little theoretical research on the synthesis mechanism. Therefore, the kinetics of the coprecipitation reaction and pyrolysis reaction in the preparation of Ni-Co-O composite by NiSO4-Co(NO3)2-ammonium hydroxide system is of great importance and was investigated in this study. The main work is as follows:(1) The reactive crystallization kinetics of the coprecipitation reaction by NiSO4-Co(NO3)2-ammonium hydroxide system was investigated under continuous steady state. Results showed that the growth rate of crystal product was size-dependent. The MJ2、MJ3、ASL、Bransom、CR size-dependent growth rate models were discussed based on the theory of population balance. It was found that the MJ3 model was the best one. In addition, the growth rate equation of different residence time and ratio of reactants was determined by using the MJ3 model.(2) The kinetics of the thermal decomposition process for the precursors produced at Ni:Co=1:0,3:1,2:1,1:1,0:1, respectively, was investigated by TG (DSC) techniques with different heating rates. The methods of Kissinger, Coats-Redfern and Flynn-Wall-Ozawa (FWO) were used to solve the parameters of thermal decomposition dynamics,including activation energy, the pre-exponential factor and reaction order. The thermal decomposition reaction kinetics at different ratio of reactants were determined as G(a)=-1n(1-a) for cobalt and G(α)=(1-a)-1-1 for nickel and nickel/cobalt complexes.