The Preparation Of VOPO₄·2H₂O And SnO₂/PANI Material And Their Capacitance Performance

Over the years, supercapacitors especially pseudocapacitors have attracted considerable attention considering their high power density,so the characterization and electrochemical performances of VOPO4?2H2O and SnO2/polyaniline were investigated in this paper..1. A systematic comparison of VOPO4·2H2O prepared by reflux and hydrothermal methods was carried out. The samples synthesized by both methods consisted lamellar particles. The material synthesized by reflux method showed a nummular morphology with an average diameter of about 5 ?m. However, the material synthesized by hydrothermal method exhibits a square platelet with an average diameter of about 10 ?m. The material synthesized by reflux method had better performance in the capacitance than that by hydrothermal method(102 F g-1),and its the specific capacitance was up to 202 F g-1 at 2 mV s-1 in 6 mol L-1 H3PO4 electrolyte. 67.4% of capacitance was maintained for the VOPO4?2H2O synthesized by reflux method. The energy density of VOPO4?2H2O supercapacitor synthesized by reflux method was 18.7 Wh kg-1 while the power densities was 290 W kg-1.2. A novel one-pot synthesis method is used to prepare SnO2 and SnO2/polyaniline nanocomposites. We found that the pure SnO2 synthesized by the(NH4)2S2O8 was solid ball with average diameter about o.2 um. On the contray, the SnO2 synthesized by the H2O2 was hollow ball. However, a PANI layer of SnO2/polyaniline nanocomposites synthesized by the(NH4)2S2O8 was coated on the solid SnO2 particles, with thickness in the range from 5 to 100 nm. The nanocomposites synthesized by the H2O2 occurred together. The specific capacitance of SnO2/polyaniline composite synthesied by the(NH4)2S2O8 was up to 193 F g-1at0.5 A g-1, its energy density was 22.4 Wh kg-1 at 240.9 W kg-1 in 1 mol L-1 H2SO4 electrolyte. The properties were superior than the corresponding SnO2, after 5000 cycles, the capacitance retention was 94.8%.3. A one-pot synthesis method is used to prepare SnO2 and SnO2/polyaniline nanocomposites. The synthesis conditions of SnO2/polyaniline were investigated including temperatures(room temperature and ice-bath) and oxidant((NH4)2S2O8,Na2S2O8 and K2S2O8). We found that all the sameples showed the similar shape, the irregular nanostructured PANI layer is coated on the surface of SnO2 hollow ball. The specific capacitance of SnO2/polyaniline composite synthesied by the(NH4)2S2O8,Na2S2O8 and K2S2O8 were 239 F g-1 ? 230 F g-1 ? 280 F g-1 under ice-bath,respectively,which is higher than that in the room temperature.The results showed that the materials synthesized by K2S2O8 under ice-bath had higher energy density and power density, which is 32.6 Wh kg-1 and 241.6 W kg-1 at 0.5 A g-1, after 5000 cycles,its capacitance retention was lower the other samples which was 87.9%.