Photocatalytic Hydrogen Production Via Water Splitting Using Different Gold-Based Catalysts

Abstract

In order to avoid serious environmental and economic damages from energy use, humans must stop using fossil fuels altogether, as soon as possible. One possible strategy to cut the dependence of fossil fuels and, at the same time create a new economic force, is to develop a hydrogen based energy economy. A potentially viable way forward is to produce H2 from water by combining solar energy and heterogeneous photocatalysts. For these reasons the objectives of this investigation were: 1) synthesize a high surface area TiO2 nanowires (NWs) catalyst in the rutile phase, 2) incorporate different amount of gold nanoparticles into the as-synthesized catalyst and into the commercial form of TiO2 (Degussa P-25) using a chemical reduction method, 3) produce hydrogen via water splitting using visible and ultraviolet light. The hypotheses of the study were: a) The catalyst with the biggest surface are will produce the biggest amount of hydrogen, and b) The gold nanoparticles will enhance the hydrogen production and will allow the use of visible light, diminishing the semiconductor’s band gap and working as an electron trap. Interestingly, the incorporation of gold nanoparticles into the titania surface enhanced the surface area in both P25 and TiO2 NWs. The hydrogen production obtained by using Au/P25 catalysts was measured to be 800 μmolg-1h-1 under irradiation at 400 nm and 1,436 μmolg-1h-1 using Au/TiO2 NWs at the same wavelength. Both of the hypotheses were correct and all the objectives achieved. The characterization of the synthetized compounds were performed with: 1) X-ray diffraction (XRD) to confirm the crystalline form of the TiO2 synthetized nanowires. 2) Field emission Scanning Electron Microscopy (FESEM), to confirm the morphology of the synthetized compound. 3) Brunauer, Emmett and Teller (BET) instrument to measure the surface area of the gold based nanowires and the commercial TiO2 form P-25. 4) The hydrogen production was measured using a Gas Chromatographer with a Thermal Conductive detector (GC-TCD) attached to a solar simulator. 5) Ultra Violet Visible spectroscopy (UV-VIS) was used to obtain the absorption spectrums of the synthetized TiO2 rutile phase nanowires before and after the gold deposition. Finding renewable sources of energy is one of the biggest challenges of the 21st century and this investigation contributes into that.