NBEXP0018

=NBEXP0018 — Graphite/TiO2 films=

=Objective=

To make films identical to the graphene oxide/TiO2 films made in EXP0017 but with graphite in place of graphene oxide to see whether reduced graphite oxide gives superior films.

=Procedure=

1. Make and clean FTO slides 2. Measure resistivity of slides (3 points) 3. Make up graphite in ethanol solution. 1mg per 100 ml. 4. Make up 4mg/ml graphite/ST-01 TiO2 solution 5. Make up the following solutions: 6. Irradiate each solution under UV for 1 hour with stirring (known rate) & N2 bubbling (known rate?) 7. Deposit solutions onto FTO slides prepared earlier (program 'N') 8. Measure photocurrent, photovoltage & IV curves
 * Solution || ml graphite soln || ml TiO2 soln || ml ethanol ||
 * 1 || 0 || 1.0 || 4.0 ||
 * 2 || 0.3 || 1.0 || 3.7 ||
 * 3 || 0.6 || 1.0 || 3.4 ||
 * 4 || 0.9 || 1.0 || 3.1 ||
 * 5 || 1.2 || 1.0 || 2.8 ||
 * 6 || 1.5 || 1.0 || 2.5 ||
 * 7 || 1.8 || 1.0 || 2.2 ||
 * 8 || 2.1 || 1.0 || 1.9 ||

=Results=

Photocurrent results
(Baseline correction was performed using Fityk.) There is a clear degredation in the photocurrent differential over time.

This chart compares the relative generated photocurrent of each sample for each on/off cycle. It shows that 1. the variation between samples is not huge; for example sample 5 only generates about 5-8% more current than does Sample 1; 2. that the relative differences do not change much over time i.e. the degredation rate is similar for all samples.

Photovoltage results


Response of the graphite-TiO2 films to UV light. The positive voltage shift is small relative to the average baseline shift with different graphite loadings. The shape of the voltage shift pulse is reasonably consistent within each sample measurement but very variable when compared with the shape of the graphs of other samples. The variation of the baseline voltage or the shape of the peaks do not seem to correlate with the amount of graphite present in each sample.



Graph of the difference between the on- and off-peak measurements for each sample. The UV light was switched on at 120, 240, 360, 480, 600 and 720 seconds and off at 180, 300, 420, 540 and 780 seconds; the last 10 seconds of each on/off pulse (to allow for equilibration time) were used to calcluate the values for the above graph. For example, the values recorded from 230-240s (off cycle) were subtracted from 170-180 (on cycle) to calculate the differential for Pulse 1.

The voltage shift is generally less than +50mV. The values from sample 4 are highly variable (as can be seen from the raw data) and the very large error bar at Pulse 3 is also due to sample 4. The error bars are +/- 1 standard deviation.

The measurements over the entire 10 minutes were averaged and plotted above to see if the baseline shift correlates with graphene amount. There is no obvious correlation (linear, exponential etc.); there may be a characteristic V shape centered around sample 5, but the experiment would have to be repeated to see if this is the case.

=Discussion=

=Conclusion=

=Log=

=Tags=