Photon to current change process: 1. Ruthenium compound Photo-Sensitizers adsorbed on the Titanium Oxide surface absorb photon flux falling on it. 2. The Photo-Sensitizers are energized from the ground position (S) to the energized position (S∗) due to the MLCT (metal ligand charge transfer) change. The energized electrons are inserted into the conduction band of the Titanium Oxide electrode, consequential in the oxidation of the Photo-Sensitizer S + hν →S∗ [1] S∗ → S+ +e− (Titanium Oxide) [2] 3. Inserted electrons in the conduction band of Titanium Oxide are moved b/w Titanium Oxide Nano-particles with dispersal towards the back contact (TCO) and therefore arrive at the counter electrode via the exterior load and wires. 4. The oxidized photo-sensitizer (S+) receives electrons from the I− ion redox mediator, regenerating the ground condition (S), and I− is oxidized to the oxidized condition, I3−. S++e− →S [3] 5. The oxidized redox mediator, I3−, disperses toward the counter electrode and is re- reduced to I− ions. I3− + 2e− →3I− [4] In general, without permanent chemical transformation, electric power is generated The performance of a Dye Sensitized Solar Cell is majorly based on 4 energy levels of the element: • the energized state (approximately LOWEST UNOCCUPIED MOLECULAR ORBITAL) and the • ground state (HIGHEST OCCUPIED MOLECULAR ORBITAL) of the Photo-Sensitizer, • the Fermi level of the Titanium Oxide electrode, w... ... middle of paper ... ...to-current concentration for monochromatic irradiation, λ is the wavelength, and Θ is the monochromatic light intensity. As shown in the above figure, solar cells sensitized by the Ru complex Photo-Sensitizers can efficiently convert visible light to current. N3 dye (RuL2(NCS)2) responds to light from 400 to 800 nm, and black dye (RuL’(NCS)3) responds to the near-IR region up to 950 nm. • The INCIDENT PHOTON-TO-CURRENT CONVERSION EFfiCIENCY of the N3 dye- sensitized solar cell reaches 80% at 550 nm and exceeds 70% in the region from 400 to 650 nm. Taking into consideration losses due to light reflection and absorption by the TCO substrate, the internal photon-to-current conversion efficiency is effectively 90 to 100%, indicating high performance of the DYE SENSITIZED SOLAR CELL . INCIDENT PHOTON-TO-CURRENT CONVERSION EFfiCIENCY is also given by the following equation
Therefore any changes in the cell are ascribable to the working electrode. The control of potential of working electrode with respect to reference electrode is equivalent of the controlling of energy of electrons within the working electrode. As shown in Fig. 1.3, scanning the potential in the negative direction makes the electrode a stronger reductant, whereas scanning the potential in the positive direction makes it a better
Using the spectrophotometer, the absorption of each sample was measured by scanning the wavelengths. After calibrating the spectrophotometer with the blank test tube, each sample was placed into the spectrophotometer and read at 360nm. Observations were continued for each pigment sample increasing the wavelength by 20nm increments. Once these absorbance values were recorded, absorption spectra for each pigment were graphed.
When conducting Part B, formation of precipitate, change in color, difference in temperature and gaseous reactions all took place. However unlike Part A more responsive results were recorded.
The “blue-bottle” experiment demonstrates a redox reaction. This is one of the most common reactions in chemistry. Redox reactions are the movement of electrons from one substance to another. The word “redox” comes from the concepts of reduction and oxidation. Reduction is the intake of an electron by an atom. Oxidation is the opposite. It is the loss of an electron by an atom. These two reactions go hand in hand because in a chemical reaction, one reaction cannot happen without the other.
Varying the n value carries out the experiment. Absorbencies of each of the ZLn complexes are obtained. The sum of the concentrations of the metal, Z, and the ligand, L, are kept equal. With the ratio of the ligand to the metal in the solution with the maximum absorbance for the ZLn complex, the value of n can be determined as well as the composition of ZLn.
Oxidation-reduction reactions can be used to stereochemically control and produce many different organic molecules. The oxidation step in this process increases the number of carbon oxygen bonds by losing a hydrogen and breaking that bond. Through the reduction step, carbon-oxygen bond is broken and the hydrogen is returned.
Online, Chemistry, ed. "Solar Powering the World." Solar Energy (Photovoltaic Cells). 29 July 2008 .
When introduced into an ionic solution, positively charged ions will be electrostatically attracted to the anode and the negatively charged ions will be electrostatically attracted to the cathode. This act of moving ions means that charges are able to move from anode to the cathode and complete the circuit. These moving ions are essentially the same as moving electrons (electricity). This process of putting electrodes into a solution, using a direct electric current (D.C.), and separating chemicals based on their charge is known as electrolysis
This is the first reaction in the Harcourt Essen experiment. The iodine is oxidised to produce I2 wh...
Azo compounds are those having R-N=N-R΄ functional group, where R and R΄ can be either aryl or alkyl. It is a derivative of Diazene (Diimide) NH=NH, where both the hydrogen replaced by hydrocarbonyl group e.g PhN=NPh (Azobenzene or diphenyldiazene). The N=N is called as azo group. As a consequence of π – delocalization phenyl azo compounds have vivid colour like red, yellow and orange, due to this, it is used as a dye and known as azo dye [3]. Azo compounds have been incorporated into a wide variety of materials and molecular architectures, dendrimers, polymers and molecular glasses. Due to clean and efficient photochemical isomerisation and substantial change in material properties during light irradiation it has been investigated as an active
Although Solar Energy is a flexible source of where energy could be directly or indirectly converted into forms of energy, it’s still not perfect. With its inefficiency, scientists are trying to find alternative solution to store solar cells for as long as possible. The main process of capturing solar energy happens at the nanoscale. With solar cells, it gets more efficient the tinier it gets. The converting rate of solar energy is equally price competitive as fossil fuel, with a dollar per watt of solar energy. With the help of nanotechnology, it could help raise solar energy conversion efficiency and help lower costs making it the ultimate method of raw energy conversion. To make sure the process of generating energy is kept at a low cost and energy output...
When a metal cation (M) reacts with a ligand (L) a complex forms. The ligand acts as a Lewis base in the reaction and forms a coordinate covalent bond as the ligands lone pair goes to an empty orbital within the metal. To illustrate this: xM + yL → MxLy where x and y are stoichiometric ratios. To determine the ratios it is possible to use Job’s method. Also known as continuous variance, Job’s method carefully used reactant mixtures such that the total moles and volumes of reactants are constant [Harris, 2010].When just enough of the metal and ligand react the most product is formed. Measuring the absorbance of each solution, the absorbance can be plotted versus a mole fraction of metal or ligand. Using the two resulting equations the mole ratio can be determined. Absorbance is measured by ultraviolet-visible spectroscopy. This method uses visible light and ultraviolet light to excite an electron within a molecule. This will release a photon colored as what colors the molecule doesn’t absorb as the electron returns to its previous energy level. The UV-vis spectroscopic machine then uses this to measure absorbance [Misra 2002]. In this experiment, iron (II) will react with 1, 10-phenanthroline (shown below) to form iron (II)-phenanthroline. This reaction is shown as:
Photocatalysis Photocatalysis is a rapidly developing field of research with a high potential for a wide range of industrial applications, which include mineralization of organic pollutants, disinfection of water and air, production of renewable fuels and organic syntheses. The word “photocatalysis” is of Greek origin and is composed of two parts : the prefix “photo” (phos : light) and the word “catalysis” (katalyo : break apart,decompose). The main difference between a conventional thermal catalyst and a photocatalyst is that the former is activated by heat whereas the latter is activated by photons of appropriate energy. Photocatalysis refers to the oxidation and reduction reactions on semiconductor surfaces, mediated by the valence band holes and conduction band electrons, which are generated by the absorption of ultraviolet or visible light radiation. Pairs of photo-generated holes (h+) and electrons (e-) induce the formation of aggressive species such as hydroxyl or superoxide radicals from the moisture and atmospheric oxygen.
Cyclic voltammetric and amperometic measurements will be performed to measure and detect the current at the working electrode and plotted versus the applied voltage. Electrochemical window of working electrode and electrolyte solution can examine the oxidation/reduction peak of redox species. If absence of redox analyte the cyclic voltammogram will form rectangular shape as voltage constantly varies the current will get to steady state. GO (0.5 g/mL) will be added in to 0.05M Sodium Perborate (PBS) solution. 30 continuous Cyclic voltammograms will be executed in the potential range between 0 to -1.5 V while scan rate at 30 mV/s. A cathodic peak will emerge at -1.0 V with an onset potential of -0.75 V during first cathodic potential scan. Cathodic peak will be disappearing completely after several cycles.
This is commonly prepared using the Adams fusion method. Iridic acid (H2IrCL6 .xH2O) NaNO3 is mixed with a solvent such as ethanol at 70oC for about 6 hours and then heated to 500oC for an hour [2]. This process should produce pure iridium oxide. The problem, however, is that iridium is expensive, according to one source the current price of iridium is 970 USD/troy ounces. this has led to the use of catalyst supports to reduce the amount of iridium oxide to be used. According to Polonsky et al 2012, this support needs to be cheap and easily accessible. He goes on to explain that using a support is beneficial in crystalline size is reduced and homogeneity of the catalyst is improved, the catalytic activity is improved and that the catalyst supported particles are larger and hence have more active sites. The author also summarises that the three most important aspects to look at when choosing an electrocatalyst should be long-term stability, high specific surface area and decent electron conductivity. To this end, many supports are being examined such as TaC (tantalum carbide) and TiO2 just to name a few. The Adams fusion method is modified to include the support chosen [3]. In the works on Polonsky et al, 2012 it is observed that the Adams fusion method is altered such that different weight percentages of the support and the iridium oxide electrocatalyst are synthesized