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 composes 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 hole (h+) and electron (e-) induce the formation of aggressive species such as hydroxyl or superoxide radicals from the moisture and atmospheric oxygen. These species are strong enough to oxidize and decompose organic materials or smelling gas and kill bacteria (see Fig 1). Several metal
The hydroxyl radical is the most important reactive species responsible for the destruction of the organic pollutant.
1.2.1.2. Sonolytic
That familiar fizzing you hear when you drop an Alka Seltzer tablet into a glass of water is the result of a chemical reaction, and chemical reactions are extremely prevalent when it comes to what living things do to carry out life processes. In addition, environmental conditions can alter the results of chemical reactions, and in this lab, we will be answering the
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.
The purpose of the experiment is to study the rate of reaction through varying of concentrations of a catalyst or temperatures with a constant pH, and through the data obtained the rate law, constants, and activation energies can be experimentally determined. The rate law determines how the speed of a reaction occurs thus allowing the study of the overall mechanism formation in reactions. In the general form of the rate law it is A + B C or r=k[A]x[B]y. The rate of reaction can be affected by the concentration such as A and B in the previous equation, order of reactions, and the rate constant with each species in an overall chemical reaction. As a result, the rate law must be determined experimentally. In general, in a multi-step reac...
In this experiment, the calcium carbonate was in the form of marble chips. The calcium carbonate reacted with hydrochloric acid when the acid was poured into marble chips. Due to calcium carbonate’s higher reactivity, it displaced hydrogen in the hydrochloric acid. As a result, products of calcium chloride, carbon dioxide and water were formed. As the chemical reaction occurred, the water in the measuring cylinder was displaced and gas bubbles that were blowing out represented carbon dioxide.
The Change in O2 Bubbles Produced When Changing the Environment of an Enzyme. Introduction Lab 5 Exploring Enzyme Activity. We are provided a chance to understand how the enzyme catalase can turn a toxic product hydrogen peroxide into a non-toxic product. We will be utilizing a potato in this experiment because it contains the enzyme catalase.
In order to gain strong insight into the surface chemistry of silica we have perform a thorough literature search. Our goal is to identify the pioneer research performed on silica and silica supported catalyst. Particular interest lies in silica-water-cobalt and silica-alcohol-cobalt systems. This study is both on macro and micro level so that a complete theoretical base can be established. From this theoretical knowledge, key areas to look upon will be identified and a design of experiments will be established. The goal is to develop a both efficient and effective product (catalyst) using a novel methodology developed from past research.
An Investigation into the Decomposition of Hydrogen Peroxide Aim: To investigate the rate of decomposition of H2O2 with different amounts of catalyst (MnO2). Hypothesis: When H2O2 and a catalyst are mixed together, the catalyst would break down H2O2 into water and oxygen. This will result in bubbles being produced. With the data of these oxygen bubbles, the rate at which H2O2 decomposed could be found out. 2H2O2 (l) à2H2O + O2 The controlwould be to maintain the same temperature (room temperature) and to use the same amount of hydrogen peroxide (10ml) in all the tubes.
Predictions may be made about the suitability of possible catalysts by assuming that the mechanism of catalysis consists of two stages, either of which can be first:
Photosynthetic pigments are essential for life because they allow photosynthesis to occur by capturing sunlight which is then used alongside carbon dioxide and water to form organic compounds such as glucose and oxygen. The pigments allow the conversion of light energy to chemical energy which other organisms can benefit from. Oxygen is utilised by other organisms in aerobic respiration. The different pigments present in the chloroplasts allow a wide variety of wavelengths of light to be absorbed for efficient photosynthesis and provide colours to the plant to attract pollinators.
1999, 71, 181-215. Minear, R., Amy, G.. Water Disinfection and Natural Organic Matter: History and Overview. ACS Symposium Series -. 1996, 649, 1-9. Richardson, S. Water Analysis: Emerging Containments and Current Issues. Journal of Analytical Chemistry. 2003, 75, 2831-2857.
Plontke, R. (2003, March 13). Chemnitz UT. TU Chemnitz: - Technische Universität Chemnitz. Retrieved April 1, 2014, from http://www.tu-chemnitz.de/en/
Haldar et al. Hybrid Colloidal Au-CdSe Pentapod Heterostructures Synthesis and Their Photocatalytic Properties. Appl. Mater. Interfaces 2012, 4, 6266-6272
Today, the phenomenon has many practical applications such as alarm systems that activate when the flow of light is interrupted. Photoelectricity also helps explain the physics of photosynthesis, by which plants make their own food. It's truly evident that the photoelectric effect and its explanation played an important historical role in science.
The output phosphor, made of zinc cadmium sulfide, is where the electrons produced through photoemission will interact and produce light. It is extremely important that the path of the electrons from the photocathode to the output phosphor be precise.
There are many different ways that we as the earths population are destroying the environment. For example, the tall cooling towers used by industries. They do not remove pollutants but simply push them higher into the atmosphere, in this way they reduce their concentration at that particular area. The pollutants may then travel over large distances and produce negative effects in areas far away from the original site.