Hydrogen Production from Water Splitting using Nanotubes
Lastly, equal volume of methanol was added to each of the 4 solutions to create a 10% methanol mixture containing the Cu-TiO2 nanotubes. The total volume of each of the 4 solutions was 205 ml. The solutions were then placed into a self-designed reactor, one at a time, in order to measure the amount of hydrogen gas the various solutions Cu-TiO2 nanotubes could produce. Each of the hydrogen production test lasted for 1 hour. The self-designed reactor can be described by the following image: |
The photocatalytic reaction was performed in an inner-irradiation Pyrex reactor with a 400 W high pressure Hg lamp (Riko, UVL-400HA) as the light source. The peak wavelength of the lamp was centred at 365 nm. To maintain a constant reactor temperature at 25 °C, a quartz jacket, which was cooled with recycled water, was employed to cover the lamp. This separated the lamp and the solution physically. A magnetic stirrer was placed at the bottom of the reactor to ensure homogeneity of the suspension during reaction.
Gas produced via the photocatalytic reaction was first collected by a water displacement gas trap, from which the volume of the trapped gas can be determined. The mass of the water displaced by the hydrogen gas was also recorded every 2 minutes using a data-logger to measure the rate of hydrogen production. To ensure that the displacement is caused only due to hydrogen gas, the water placed in the displacement jar contained NaOH so as to remove the CO2 produced during photocatalysis. A small volume of the gas was periodically extracted by a gas tight syringe, through a silicon septum on the gas trap for gas chromatography (GC) analysis. The hydrogen concentration was then evaluated using an Agilent 7890A GC with a thermal conductivity detector (TCD) and a HP-PLOT MoleSieve/5A column. With reference to the standard TCD curve for hydrogen gas, the amount of hydrogen produced was also calculated.
Gas produced via the photocatalytic reaction was first collected by a water displacement gas trap, from which the volume of the trapped gas can be determined. The mass of the water displaced by the hydrogen gas was also recorded every 2 minutes using a data-logger to measure the rate of hydrogen production. To ensure that the displacement is caused only due to hydrogen gas, the water placed in the displacement jar contained NaOH so as to remove the CO2 produced during photocatalysis. A small volume of the gas was periodically extracted by a gas tight syringe, through a silicon septum on the gas trap for gas chromatography (GC) analysis. The hydrogen concentration was then evaluated using an Agilent 7890A GC with a thermal conductivity detector (TCD) and a HP-PLOT MoleSieve/5A column. With reference to the standard TCD curve for hydrogen gas, the amount of hydrogen produced was also calculated.
Owning to the limitation of off-line GC analysis, air trespass was inevitable, leading to viewable peaks of O2 and N2. However, since the ratio of detected O2 and N2 corresponded exactly to that of ambient surrounding air and neither O2 nor N2 was supposed to be produced during the photocatalytic reaction, both gases were deemed adventitious and the concentration of H2 was calculated without their due consideration. This figure presents a standard GC-TCD spectrum of the gas product. Note that helium was used as the carrier gas; hence H2 peak was negative and relatively small. The area above the negative peak for hydrogen gas was then used to calculate the amount of hydrogen gas produced for each of the 4 spectrums in comparison with the standard spectrum.