Lab 5

May 9th, 2014

Today our lab consisted of light absorption and Photoelectrochemical (PEC) testing.

Figure 1. Light Source

The first stage of the lab was calculating the light absorption of our substrates. Since the actual absorption rate is difficult to test by itself, it was estimated through calculating the reflection and transmission percentages and subtracting those values from the total light emitted onto the substrate. The machine in Figure 1 was used to produce the light source into a fiber optic cable which could concentrate the light onto the substrate.

Figure 2. Setup for
Transmission testing

Figure 3. Setup for
Reflection testing

The transmission percentage was tested first using the setup in Figure 2. The substrate was placed in between the two black blocks in the path of the light produced from the fiber optic cable. The light transmitted was calculated by measuring the amount of light that passed through the substrate.

The reflection percentage was found using the setup in Figure 3. The substrate was placed inside the black cylinder. This was done in order to make sure that only the light transmitted through the substrate escaped and allowed for the light reflected to be measured through the output cable. 

From calculating the reflection and transmission percentages of the light emitted, the light absorbed could be estimated through subtracting those percentages from 100%.

Figure 4. PEC Testing
Setup

The final stage of the lab was the PEC testing. This test was conducted by placing the substrates in a solution of Sodium Hydroxide inside the illuminated cube setup seen in Figure 4. The illumination provided a light source for the substrate to produce a voltage, acting as an anode, and driving the water splitting reaction through the Platinum cathode. No actual water splitting was conducted, however the efficiency of the substrate was measured through the final current read through the cathode giving us an idea of how much power could be produced through the substrate and therefore, how much hydrogen could be produced.