Laser-Induced Photocatalysis and its Applications in Petrochemicals ...

120100Methanol yield (µmol)80604020Figure 400 10 20 30 40 50 60 70 80 90 100Time (min)Hydrogen production in the presence and absence of methane overWO 3 .3.2 Photocatalytic splitting of water for generation of hydrogenTo study the photocatalytic splitting of water, pure (WO 3 , NiO, Fe 2 O 3 and TiO 2 )and doped photocatalysts, optimized amount of photocatalyst (determined from the procedurementioned earlier) was suspended in 60 ml of distilled water whereas for water splittingstudies in the presence of metal ions, the optimized amount of the catalyst was suspended in60 cm 3 solution of respective metal ion. For this purpose, a 10 ppm solution of each metal ionwas prepared by dissolving the stoichiometric amount of each metal nitrate in 1000 cm 3 ofdoubly distilled de-ionized water. In order to keep the minimum optical effects i.e. selfabsorptionof laser light by the metal ion, the strength of the solutions was selected at 10ppm.An inert atmosphere was produced by purging argon gas at a high flow rate of 200ml/min for a period of 15 minutes. The purpose of such a high flow rate was to remove all thedissolved oxygen. The progress of argon purging was studied by analyzing the gas samplefrom the dead volume of reaction chamber. All the reactions were carried out in argonenvironment and at room temperature. The other important parameters i.e. the stirring rateand beam diameter were kept constant during all measurements.SHIMADZU gas chromatograph (GC-17A) equipped with a thermal conductivitydetector (TCD) and a 30m molecular sieve 5A “PLOT” column was used to analyze thegaseous products of photocatalytic process. Argon was used as carrier gas in GC and also aspurge gas to remove dissolved oxygen from the photocatalytic reactor. The injector, columnand detector temperatures were kept at 50 o C, 50 o C and 100 o C respectively. Keeping in viewthe high concentration of O 2 in the air, the product gases were analyzed by carefullyremoving 100µl of the sample from the dead volume of the cell by using a gas tight syringe.