Photocatalyst is a generic term for photo-semiconductor materials with photocatalytic function represented by nano-scale titanium dioxide. It is coated on the surface of the substrate and under the action of light, it has a strong catalytic degradation function: it can effectively degrade toxic and harmful in the air. Gas; can effectively kill a variety of bacteria, and can detoxify and harmless toxins released by bacteria or fungi; meanwhile, it also has deodorizing and antifouling functions.
In 1972, Professor Honichi Kenta and PhD student Akira Fujishima of the University of Tokyo in Japan discovered that the use of light to irradiate a titanium dioxide electrode can perform the electrolytic reaction of water. This is the "Hondo-Fujishima effect" of the ***.
In Japan, a chemical material similar to this photocatalytic effect under light is named " photocatalyst ".
International scientific name (Photocatalyst) = Photo (Photo) + catalyst (catalyst).
Therefore, the photocatalyst can also be called a photocatalytic material.
Photocatalysts will produce a photocatalytic reaction similar to photosynthesis under the irradiation of light. It catalyzes water or oxygen in the air into hydroxyl radicals (· OH) and superoxide anion radicals (O2 ·), which are highly oxidizing, and active. Oxygen (HO2 ·, H2O2) and other photo-living groups with extremely strong oxidizing ability, the energy of these photo-living groups is equivalent to a high temperature of 3600K, and has strong oxidizing properties.
These strong oxidizing groups can effectively decompose various organic compounds and some inorganic substances with unstable chemical bonds, and can destroy the cell membrane of bacteria and the protein carrier of coagulation virus.
Photocatalyst materials mainly include nano-TiO2, ZnO, CdS, WO3, Fe2O3, PbS, SnO2, ZnS, SrTiO3, SiO2, etc. Since 2000, it has been found that some nano-precious metals (platinum, rhodium, palladium, etc.) have better photocatalytic performance. But because most of them are prone to chemical or photochemical corrosion, and the cost of precious metals is too high, they are not suitable as photocatalysts for domestic air purification.
Among all photocatalyst materials, nano-TiO2 not only has high photocatalytic activity, but also has the advantages of resistance to acid and alkali corrosion, chemical corrosion, non-toxicity, etc., the price is also moderate, and the cost-effectiveness is high. Therefore, nanometers are mostly used in the market. Titanium dioxide is the main raw material.
Nano-titanium dioxide (TiO2) is a semiconductor, which mainly has three crystal structures: Anatase, Rutile, and Brookite. Among them:
Plate titanium crystals have poor stability and are generally considered to have no photocatalytic activity.
Anatase type crystals have stronger photocatalytic performance than rutile type crystals, weather resistance and adhesion are also very good, nano-inorganic coating is stable, and the market price is higher than rutile type crystals.
Nano-sized zinc oxide (ZnO) has a particle size between 1-100 nm. It is a new type of high-functional fine inorganic product oriented to the 21st century. Capable of absorbing and scattering ultraviolet rays, using its wonderful properties in light, electricity, magnetism, sensitivity, etc., it can manufacture gas sensors, phosphors, rheostats, ultraviolet shielding materials, image recording materials, piezoelectric materials, varistor, high efficiency Catalysts, magnetic materials and plastic films. It has a wide range of applications in the fields of rubber, ceramics, textiles, printing and dyeing, and national defense.
Nanometer zirconia (ZrO2) is a high-purity white powder, which is odorless and tasteless. It is monoclinic at low temperatures and tetragonal at high temperatures. Has a high refractive index (refractive index 2.2) and high temperature resistance. It has good thermochemical stability, high temperature conductivity and high high temperature strength and toughness, and has good mechanical, thermal, electrical, and optical properties. HT-ZrO-01 is monoclinic, and HT-ZrO-02 is tetragonal. Nano-sized zirconia particles are small in size and are very stable oxides. They have the properties of acid resistance, alkali resistance, corrosion resistance, and high temperature resistance. They can be used in functional ceramics and structural ceramics, and gem materials.