Figures index

From

Electrochromism of Methylviologen (Paraquat)

N. Aristov, A. Habekost

World Journal of Chemical Education. 2015, 3(4), 82-86 doi:10.12691/wjce-3-4-1
  • Figure 1. Reaction cell with incandescent lamp (left) and luxmeter (right)
  • Figure 2. N-methyl viologen CV at different scan rates (50, 100, 300 mV/s) on Pt electrodes. The arrow shows the direction of scan rate increase. The bold curve shows the CV measured at 50 mV/s but only between -0.5 V and -1.0 V
  • Figure 3. Total light transmission as a function of applied linearly increasing/decreasing voltage between 0 and -1.5 V and back to 0 V.
  • Figure 4. A single cycle taken from Figure 3. The dashed vertical line marks the voltage turning point at -1.5 V (90 s). The solid vertical lines mark the onsets (from left to right) of reactions 1 (colorless to blue), 2 (blue to yellow), 3 (yellow to blue), and 6 (blue to colorless). The novice might need to be alerted to the fact that the potentials at which the color changes start to happen do not correspond to the peak-current potentials in the CV. The CV peak-current potentials show at which potential the reactions are most efficient, not the ones at which they can start to occur
  • Figure 5. UV/vis-spectrum of viologen, measured eight times at 20-second intervals, with an applied potential of -0.9 V
  • Figure 6. Total light transmission (solid curves) and measured voltage (dashed curves) of an FTO/Vio/FTO cell. Top: Applied voltage is -0.9 V starting at 8 s to about 25 s, then switch off of voltage to 0 V. Bottom: Applied voltage is 0 V up to 180 s, then electrolysis at -1.5 V between ~180 s and ~200 s, then switch off of electrolysis potential back to 0 V. At the electrolysis voltage of -0.9 V in the top panel viologen neutrals cannot form; but they can in the bottom panel