FAQ
These are questions that were commonly asked when we presented our project in various competitions and exhibitions. If you have burning questions, you might just find the answers to them here!
1.What is hematemesis and schizophrenia?
- hematemesis - vomiting of blood
- Schizophrenia - complex mental disorder (e.g. can’t differentiate whats real and unreal, cant think logically, cant behave normally, can’t have normal emotional responses)
2.Explain how the hydrothermal synthesis works.
- 2NaOH + TiO2 → 2Na+ + TiO32- + H2O (dissolving, giving nanosheets)
- By raising temp. the ratio of dissolved TiO3 2- to crystallized ones would change (more would dissolve rather than crystallized) (causing some layers of the nanosheets to be wider, this induces mechanical stress that makes it favourable for the sheets to curve into tubes)
- In fact, if temp. was raised to 170 degrees, we would get nanowires.
3.How much does synthesizing these nanotubes cost?
- 1kg TiO2 powder costs $200, we used only 4g
- 1 kg NaOH pellets costs $105, we only used a small amount to prepare the conc. NaOH
4.I see that u used methanol, wouldn't that be wasting methanol which can be used as fuel directly?
- 10% methanol is extremely difficult and costly to recover even by industrial standards, hence being able to fully utilize these resources would be highly beneficial.
5.Why SEM not TEM?
- We only need to ascertain its morphology to be that of nanotubes, SEM would be sufficient.
- Do not require TEM which is more expensive and requires more expertise to use
6.How does XRD works?
- X-rays are focused onto the crystalline material of the nanotubes
- X-rays then scattered and forms a spectrum with peaks of varying intensity
- From spectrum, conclude that crystalline structure of nanotubes is mainly rutile by comparing with standard spectrums
7.Does the remaining Cu in some of the solutions get precipitated out as brown solids which can be easily removed?
- Yes, remaining undeposited Cu2+ in the solution may have been reduced by photoexcited electron, giving Cu. However, as this amount is quite small, they may not be easily removed through filtering.
8.Approx., how long can the TiO2 nanotubes be used for Cu removal and Hydrogen production? (e.g. the time taken before one batch of nanotubes is saturated with Cu)
- Not sure, but we hypothesize that it would be quite fast as we did not measure the Cu2+ content over time (real-time analysis)
- depends on the ratio of TiO2 nanotubes to Cu2+, e.g. in the 100ppm solution whereby Cu2+ is largely in excess, saturation would occur extremely quickly.
9.What are the strengths of your project?
- Produces Clean water AND clean energy
- Nanotubes can be recycled
- Strives to be self-sustainable (hope to use hydrogen gas generated to fuel entire experimental procedure)
- Cheap utilization and synthesis
10.Can the TiO2 nanotubes be re-used?
- Yes, the nanotubes can be placed in regenerants to remove the copper/ heavy metal ions adsorbed onto it and then obtained through further reduction and filtration
11.What are the weaknesses to your project?
- Energy input vs output may be a concern - whether is it worth it to put in this certain amount of energy to achieve this certain amount of energy
- Saturation may occur easily when Cu2+ is in excess
12.Is the amount of hydrogen produced worth the inputs in the experiment (e.g. UV light)? (Energy input vs. Output)energy balance analysis?
- too small scale to conduct an energy balance analysis (have seeked expert advice about this), instead, our mentor suggested that we focus on improving efficiency on a small scale first
- It is green energy that is being produced.
- furthermore, very small amounts of TiO2 powder was used (4.00g to create stock solution) Should there be more TiO2 nanotubes used, we believe that hydrogen generation would significantly increase due to the presence of more water reduction sites.
- Carbon-sensitizing → lower bandgap → utilize solar energy
13.How would this technology be implemented?
- Through industrializing in a column in reactor (a segment in the reactor can be partitioned out to contain the suspension of TiO2 nanotubes, whereby water would pass through it several times for thorough purification)
14.Would it work on other heavy metal ions?
- In theory, yes - heavy metal ions are adsorbed onto the nanotubes through bonding to the hydroxyl groups on their surface
- But whether or not hydrogen generation would be promoted depends on the type of metal ion adsorbed (e.g. if the conduction band of the metal is higher than TiO2 then recombination would not be prevented--> hydrogen generation not increased)
15.What do you mean when you say you plan to carbon-sensitize the nanotubes? How does that increase the efficiency?
- by carbon sensitizing the nanotubes, it forms a photoactive layer, which greatly increases the power conversion efficiency from the sunlight. the carbon layer facilities exciton dissociation at the junction by charge transfer. as a photon is absorbed by the carbon layer, it induces an electron injection into the conduction band of titania. This helps to collect a greater spectrum of sunlight (refer to http://en.wikipedia.org/wiki/Hybrid_solar_cell from ‘Dye Sensitized’ subheading onwards
- so that sunlight can be used to power the photocatalytic hydrogen generation process (sunlight cheaper and readily available) instead of UV light
CLEARER EXPLANATION: Ti has 2 valence electrons whereas C has 4. Thus if some Ti were substituted with C, there would be 2 loosely held electron (more unstable--> higher energy level) on each C. This raises the material’s fermi level (highest energy of electron at ground state) and lesser energy would be needed to excite these electrons to the conduction band, thus solar light which is of lower energy can be utilized.
16.What do you mean by doping?
- Introducing another substance into the crystal structure of the nanotubes (substituting one oxygen atom with another), e.g. nitrogen as we have read from literature
- Either lowers energy level of conduction band or raise energy level of valence band, but unsure of how it goes about achieving this
1.What is hematemesis and schizophrenia?
- hematemesis - vomiting of blood
- Schizophrenia - complex mental disorder (e.g. can’t differentiate whats real and unreal, cant think logically, cant behave normally, can’t have normal emotional responses)
2.Explain how the hydrothermal synthesis works.
- 2NaOH + TiO2 → 2Na+ + TiO32- + H2O (dissolving, giving nanosheets)
- By raising temp. the ratio of dissolved TiO3 2- to crystallized ones would change (more would dissolve rather than crystallized) (causing some layers of the nanosheets to be wider, this induces mechanical stress that makes it favourable for the sheets to curve into tubes)
- In fact, if temp. was raised to 170 degrees, we would get nanowires.
3.How much does synthesizing these nanotubes cost?
- 1kg TiO2 powder costs $200, we used only 4g
- 1 kg NaOH pellets costs $105, we only used a small amount to prepare the conc. NaOH
4.I see that u used methanol, wouldn't that be wasting methanol which can be used as fuel directly?
- 10% methanol is extremely difficult and costly to recover even by industrial standards, hence being able to fully utilize these resources would be highly beneficial.
5.Why SEM not TEM?
- We only need to ascertain its morphology to be that of nanotubes, SEM would be sufficient.
- Do not require TEM which is more expensive and requires more expertise to use
6.How does XRD works?
- X-rays are focused onto the crystalline material of the nanotubes
- X-rays then scattered and forms a spectrum with peaks of varying intensity
- From spectrum, conclude that crystalline structure of nanotubes is mainly rutile by comparing with standard spectrums
7.Does the remaining Cu in some of the solutions get precipitated out as brown solids which can be easily removed?
- Yes, remaining undeposited Cu2+ in the solution may have been reduced by photoexcited electron, giving Cu. However, as this amount is quite small, they may not be easily removed through filtering.
8.Approx., how long can the TiO2 nanotubes be used for Cu removal and Hydrogen production? (e.g. the time taken before one batch of nanotubes is saturated with Cu)
- Not sure, but we hypothesize that it would be quite fast as we did not measure the Cu2+ content over time (real-time analysis)
- depends on the ratio of TiO2 nanotubes to Cu2+, e.g. in the 100ppm solution whereby Cu2+ is largely in excess, saturation would occur extremely quickly.
9.What are the strengths of your project?
- Produces Clean water AND clean energy
- Nanotubes can be recycled
- Strives to be self-sustainable (hope to use hydrogen gas generated to fuel entire experimental procedure)
- Cheap utilization and synthesis
10.Can the TiO2 nanotubes be re-used?
- Yes, the nanotubes can be placed in regenerants to remove the copper/ heavy metal ions adsorbed onto it and then obtained through further reduction and filtration
11.What are the weaknesses to your project?
- Energy input vs output may be a concern - whether is it worth it to put in this certain amount of energy to achieve this certain amount of energy
- Saturation may occur easily when Cu2+ is in excess
12.Is the amount of hydrogen produced worth the inputs in the experiment (e.g. UV light)? (Energy input vs. Output)energy balance analysis?
- too small scale to conduct an energy balance analysis (have seeked expert advice about this), instead, our mentor suggested that we focus on improving efficiency on a small scale first
- It is green energy that is being produced.
- furthermore, very small amounts of TiO2 powder was used (4.00g to create stock solution) Should there be more TiO2 nanotubes used, we believe that hydrogen generation would significantly increase due to the presence of more water reduction sites.
- Carbon-sensitizing → lower bandgap → utilize solar energy
13.How would this technology be implemented?
- Through industrializing in a column in reactor (a segment in the reactor can be partitioned out to contain the suspension of TiO2 nanotubes, whereby water would pass through it several times for thorough purification)
14.Would it work on other heavy metal ions?
- In theory, yes - heavy metal ions are adsorbed onto the nanotubes through bonding to the hydroxyl groups on their surface
- But whether or not hydrogen generation would be promoted depends on the type of metal ion adsorbed (e.g. if the conduction band of the metal is higher than TiO2 then recombination would not be prevented--> hydrogen generation not increased)
15.What do you mean when you say you plan to carbon-sensitize the nanotubes? How does that increase the efficiency?
- by carbon sensitizing the nanotubes, it forms a photoactive layer, which greatly increases the power conversion efficiency from the sunlight. the carbon layer facilities exciton dissociation at the junction by charge transfer. as a photon is absorbed by the carbon layer, it induces an electron injection into the conduction band of titania. This helps to collect a greater spectrum of sunlight (refer to http://en.wikipedia.org/wiki/Hybrid_solar_cell from ‘Dye Sensitized’ subheading onwards
- so that sunlight can be used to power the photocatalytic hydrogen generation process (sunlight cheaper and readily available) instead of UV light
CLEARER EXPLANATION: Ti has 2 valence electrons whereas C has 4. Thus if some Ti were substituted with C, there would be 2 loosely held electron (more unstable--> higher energy level) on each C. This raises the material’s fermi level (highest energy of electron at ground state) and lesser energy would be needed to excite these electrons to the conduction band, thus solar light which is of lower energy can be utilized.
16.What do you mean by doping?
- Introducing another substance into the crystal structure of the nanotubes (substituting one oxygen atom with another), e.g. nitrogen as we have read from literature
- Either lowers energy level of conduction band or raise energy level of valence band, but unsure of how it goes about achieving this