Solar Water Splitting
9 Pages Posted: 10 Jul 2017
Date Written: March 3, 2014
85% of current energy consumption is by fossil fuels which produce CO2. We need a clean fuel to replace fossil fuels. Hydrogen serves as a clean fuel which can be produced by water splitting using renewable energy sources. Semiconductors have potential to meet the thermodynamic requirement to split water. Semiconductors have electrical conductivities between those of metals and insulators. Those have an energy level gap where no electronic state exists. This gap separates the valence and conduction bands. This gap is the band gap. Band gap defines which types of light the semiconductor can absorb. Band gap was measured by a UV-Visible Spectroscopy. This technique measures the percentage reflectance of the material. The Tauc equation was used to measure the absorption of the material from the reflectance data. Tauc plots will show the band gap of the material. A solar simulator was used as the source for sunlight. Movement of electrons from valence band to conduction band produces current upon light absorption. Photo current has been measured using Potentiostat at different voltages. The positive end of the potentiostat was connected to working electrode(semiconductor) and negative terminal was connected to counter electrode (platinum). Copper oxide, silicon and titania were tested for water splitting as these materials are cheap and abundantly available. As copper oxide has band gap in the visible region it has shown to absorb maximum portion from sunlight compared to silicon and titania. From the current-voltage plots it has been observed that copper oxide showed better photocurrents than silicon and titania.
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