The material of the photocatalyst, which are the photocatalysts

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There are many materials that can be used as photocatalysts in the world, including titanium dioxide, zinc oxide, tin oxide, zirconium dioxide, cadmium sulfide and other oxide sulfide semiconductors, among which titanium dioxide has become the world's most popular nano photocatalyst material because of its strong oxidation ability and stable and non-toxic chemical properties. In the early days, cadmium sulfide and zinc oxide were also used as photocatalyst materials, but due to the unstable chemical properties of these two, photodissolution will occur at the same time as photocatalysis, and the dissolution of harmful metal ions has certain biological toxicity, so developed countries have rarely used them as civil photocatalytic materials, and some industrial photocatalytic fields are still used.

Titanium dioxide is a semiconductor with three crystal structures: anatase, rutile, and plate perovskite, among which only the anatase structure and rutile structure have photocatalytic properties.

Including titanium dioxide, zinc oxide, tin oxide, zirconium dioxide, cadmium sulfide and other oxide sulfide semiconductors.

Photocatalytic materials refer to a class of semiconductor catalyst materials required for photochemical reactions that occur under the action of light through this material.

A typical natural photocatalyst is chlorophyll, which promotes the synthesis of carbon dioxide and hydration in the air into oxygen and carbohydrates in the photosynthesis of plants. In general, nano photocatalyst technology is a kind of nano bionic technology, which is used in many cutting-edge fields such as environmental purification, self-cleaning materials, advanced new energy, cancer treatment, and high-efficiency antibacterial.

Both photocatalysis and metal catalysis are methods of promoting the reaction rate, but they differ in the following ways:

1.Different types of catalysts: photocatalysis uses semiconductor materials or dyes and other substances that can absorb visible light, eliminate potatoes or ultraviolet rays and produce electron-hole pairs as catalysts; Metal catalysis, on the other hand, uses metal ions and synthetic organic coordination systems as catalysts.

2.The reaction conditions are different: photocatalysis needs to be irradiated at a specific wavelength in order to excite the electron-hole pairs to react. Metal catalysis, on the other hand, is usually performed at room temperature, and the reaction rate can be controlled by adjusting the reaction conditions such as temperature, pressure, etc.

3.Different application fields: due to its special properties, photocatalysis is mainly used in environmental pollution control, water treatment, new energy development and other fields; Metal catalysis is widely used in organic synthesis, pharmaceutical manufacturing and fine chemicals.

4.Different reaction mechanisms: Although both methods accelerate the reaction rate by increasing the concentration of active intermediates, there are differences in the specific reaction mechanisms.

For example, in the process of oxygen reduction, photooxygenation will generate free radical hydroxyl groups (·OH), which will degrade pollutants; When copper ions are involved in amide bond cleavage, Cu(II) and Cu(I) cycles and other complex structures may be formed.

In conclusion, while both methods can promote the reaction rate and have some overlap, they often complement each other in practice. But there are still significant points of difference between them.

The applications of photocatalysis are as follows:

Photocatalytic energy converts solar energy into chemical energy, such as photolysis of water to produce hydrogen, photoreduction of carbon dioxide, etc., if it can be applied on a large scale, it will effectively alleviate the above contradictions. In addition, photocatalysis can also use solar energy to degrade organic pollutants, reduce heavy metal ions, and achieve self-cleaning, so it is also an ideal environmental pollution control technology. Photocatalysis has shown great application prospects in the fields of energy and environmental protection.

Photocatalysis has become one of the most active research directions in the field of scientific research due to its characteristics of using light energy residue and room temperature to complete deep reactions, and has won many important awards in basic research in this field. Especially since the discovery of the Honda-Fujishima effect, semiconductor photocatalytic technology has attracted a large number of scholars to engage in scientific research in this field.

With the expansion and depth of the research concept, photocatalytic research has been expanded to many fields such as energy, health, environment, pollution control, and synthesis. It is believed that photocatalytic technology will eventually bring great benefits to our lives because of its broad prospects.

Photocatalytic ozone oxidation is a new technology applied to air pollution control, the principle of which is to use the characteristics of photocatalyst catalyst to excite reactive oxygen species under ultraviolet irradiation, form a series of free radicals, and convert harmful substances into harmless substances through oxidation reaction.

Nanophotocatalysts are the nemesis of pollutants, and their mechanism of action is simply (as shown in the figure below): nanophotocatalysts are stimulated by the irradiation of a specific wavelength of light"Electron a hole"Yes (a high-energy particle), this kind"Electron a hole"After the action on the surrounding water and oxygen, it has a strong redox ability, which can directly decompose formaldehyde, benzene and other pollutants in the air into harmless and odorless substances, as well as destroy the cell wall of bacteria, kill bacteria and decompose its silk mesh bacteria, so as to achieve the purpose of eliminating air pollution. Specifically, if the energy of a photon is greater than the bandgap width of the semiconductor, the electrons (e-) in the valence band will be excited to the conduction band, and holes (h+) will be generated in the valence band.

Photogenerated holes have a strong oxidizing ability to attack socks, and photogenerated electrons have a strong reducing ability, and they can migrate to different locations on the surface of the semiconductor to undergo redox reactions with the pollutants adsorbed on the surface.

The theoretical basis for the use of nano-semiconductor particles [1] as photocatalysts is that, on the one hand, the quantum size effect widens the semiconductor energy gap, and the conduction band potential becomes more negative, while the valence band potential becomes more positive. This gives it a stronger redox capacity; On the other hand, the specific surface area of nanoparticles is much larger than that of conventional materials, and the surface area of nanomaterials the size of a grain of rice will be equivalent to the size of a football field. Moreover, the smaller the particle size, the smaller the chance of electron-hole recombination, and the better the effect of charge separation, which leads to the improvement of catalytic activity.

The new oxygen nanocatalytic decomposition technology is prepared by sintering nano-scale titanium dioxide materials with ultra-large specific surface area and lightweight carbon substrates through a special process, and the mass production of the materials has been completed, thus completely solving the problem of low efficiency of traditional catalytic technology.