SHArK Abstract/Summary

SHArK (Solar Hydrogen Activity Research Kit) with Pipette Method: Distributed research project examines how electrochemical responsiveness of metal oxides to visible light varies with concentration and droplet size.

The SHArK project is a distributed research project begun at the Univ. of Wyoming. It hopes to find a combination of metal oxides that will absorb visibile light and spilt water with the absorbed energy.

This research explores the potential of Cobalt, Aluminum, and Iron oxides as catalysts for spliting water into O2 and H2 gas using only sunlight. It also explores the effect of varying droplet size and metal nitrate concentration when using the pipette method to prepare test plates for the SHArK project.

A hydrogen-based economy will not be feasible without a more efficient method of producing hydrogen gas. The SHArK project is a distributed research project that engages high school and undergraduate students. In the pipette method metal nitrates in acidic solution are pipetted onto a conducting glass plate and are then baked in an oven at 500 degrees celsius for 24 hours. While in the oven, the metal nitrates oxidize to metal oxides. The plates are then rinsed and placed in a small aquarium-like tank in .1 molar sodium hydroxide solution. An electrode is connected to the plate, a counter electrode is connected to a graphite rod which is submerged in the electrolyte solution. A voltage is applied across these two electrodes. This applied voltage is called the bias. Each plate is usually scanned twice, one with a positive .5 volt bias and once with a negative .5 volt bias. Electronics controlled by a computer measure the current passing through the circut in miliAmps. Electrochemical activity of the metal oxides is examined by analyzing changes in current in the circut. When the detected current increases it is assumed that an n-type metal oxide is donating electrons to the current and thus increasing the current. When the detected current decreases it is assumed that a p-type metal oxide has opened up a hole and electrons have sank into it and thus decreasing the current. A 532 nm (which is actually a frequency-doubled 1064nm CO2 laser IIRC) green laser pointer is used to test the metal oxides for visibile light-induced electrochemistry. The laser is mounted on a LEGO(Registered Trademark) platform and LEGO Mindstorms(R) robotics control two mirrors that reflect the laser beam onto the test plate. The computer software imagines the plate as a grid of 180 collumns and 180 rows for a total of 32,400 individual data points per scan. For each data point, the computer turns on the laser, records the current, turns off the laser, and tells the robotics to move the mirrors to aim the laser at the next point. The robotics move the laser beam like a typewriter; single steps to the right until they reach the end of a row, then a long step back to the left hand edge, and a single step down. The computer ouputs a text file consisting of 32,400 numbers which is then processed using an open source program called imageJ which in turn assigns a color to each value and creates a 180 pixel by 180 pixel image of the scan. Each plate generates two images; one scanned with a positive bias and the other with a negative bias. Because the SHArK project is a distributed research project, it's website is also home to it's results database. Anyone can view the results so far of the project if they create a user account and all researchers can post their results to the main results archive.