Solar Powered Hydrogen Generation Via Carbon-Doped TiO2 Anodes
University of Delaware
Titanium dioxide has excellent qualities as a photocatalyst, yet it only absorbs light in the ultraviolet region. Narrowing the band gap via doping can increase the percentage of solar light it can utilize. When incorporated into a photoelectrochemical cell as an anode, it promotes water splitting, producing oxygen and hydrogen without any harmful byproducts. Pulsed laser deposition has proved useful for tailoring the bandgap of TiO2 by doping with nitrogen. The same technique is now being utilized to study the effect of carbon doping. Deposition experiments were conducted using a KrF excimer laser (λ = 284 nm), heating the substrate to 600ºC under 100 mTorr total gas mixture pressure, for 20 minutes of a 1.8 J/cm^2 laser fluence using a 1.6 cm substrate to target distance. Carbon dioxide did not introduce carbon into the TiO2 lattice due to the overabundance of oxygen. Methane proved to be a more successful carbon precursor. Crystallinity, a shift in preference between anatase and rutile, a red shift in band gap, and changes in thickness and grain size were observed. Visible light activity did not increase, however, due to the formation of intermediate stages in the band gap. This leads to the conclusion that carbon doping by itself is insufficient and co-doping of nitrogen and carbon should be attempted in future research.