At present, the novel coronavirus is still continuing, causing a certain degree of impact on industries and enterprises, but also affecting the hearts of people from all walks of life. Under such circumstances, China Semiconductor Lighting Network and Jingzhi Toutiao, under the guidance of the National Semiconductor Lighting Engineering R&D and Industry Alliance and the third Generation Semiconductor Industry Technology Innovation Strategic Alliance, started to share knowledge during the epidemic.

I. Introduction to photocatalysis technology

The discovery of photocatalysis came in 1972 when Akira Fujijima of the University of Tokyo first discovered that titanium dioxide (TiO2) irradiated by ultraviolet light could undergo a sustained REDOX reaction of water to produce hydrogen. The Effect became known as the Honda-Fujishima Effect, a combination of the names of Professor Fujijima and his advisor at the time, ---- Kenichi Hondo, president of Tokyo Polytechnic University.

1. Introduction to photocatalytic technology

(1) The subject of photocatalysis is an emerging interdisciplinary research field of catalytic chemistry, photochemistry, semiconductor physics, materials science and environmental science.

(2) When the semiconductor is excited by ultraviolet light (wavelength less than 380nm), photogenerated electrons and electron holes are generated;

(3) The electron hole capacity reaches 3.0eV, which is equivalent to the energy at 15,000 degrees

(4) Photogenerated electrons have the properties of reduction, can reduce aquatic hydrogen, direct electricity generation - solar cell - energy utilization;

(5) Photogenic holes are highly oxidizing and can degrade or mineralize pollutants and kill bacteria and viruses -- environmental applications.

Oxidability:F2＞·OH＞O3＞H2O2＞MnO4-＞Cl2

Photocatalysis can effectively degrade almost all organic matter

Mineralize compounds containing sulfur, nitrogen and phosphorus

Efficient sterilization and disinfection

2. Principle of photocatalytic sterilization and disinfection

Hydroxyl radicals and active ionic oxygen produced by photocatalyst can oxidize bacteria and virions through the following oxidation mechanisms: coenzyme A oxidation mechanism, cell wall (membrane) destruction mechanism, DNA& RNA genetic material destruction mechanism photocatalytic sterilization, has the traditional inorganic antibacterial incomparable excellent sterilization effect, has the advantages of persistence, broad spectrum, heat resistance, no resistance, thorough sterilization, but also has the advantages of non-toxic, tasteless, no irritation to the skin, no consumption, can be used again.

It is worth noting that after the inactivation of bacterial viruses, the remains of bacteria and viruses are made of basic elements, and photocatalysis can efficiently decompose the remains and remove them. There is an endotoxin in medicine that can be broken down by photocatalysis.

There are many literatures at home and abroad on photocatalytic sterilization, including tuberculosis, hepatitis B, conventional bacteria, viruses, etc., which have been demonstrated at the mechanism, application and laboratory level, showing no problem in the effect.

2. Evaluation of photocatalytic effect

As for the evaluation, first of all, there will be the problem of standards. Compared with international standards, the current domestic standards on photocatalysis are not sound. In terms of air purification, water purification, self-cleaning of photocatalytic materials, antiviral, UV light sources for photocatalysis, there are very few standards, and they are not mandatory standards. Especially the part of violet light, not including LED UV light source.

There are still some problems in the existing standard test evaluation of photocatalysis, including: there is a big gap between the test conditions and the actual use conditions, which cannot reflect the effect of the actual use scenario; Few test institutions accept the national standard certification, unable to give effective test report.

From the perspective of Guangdong Nengjing, we designed our own photocatalytic reactor according to the national standard of air purifier. The structure is shown as follows:

With such a reactor, we tested some formaldehyde in a cube in the lab, and then bacteria, and then viruses. On the basis of sufficient data, the adaption of catalyst and light source is carried out. Once stabilized, we turn it into a standard photocatalytic unit and put it into our purification equipment to test the actual level of use of the purifier or sanitizer.

It is worth mentioning that the test found that within an hour, a cubic bin of formaldehyde degradation efficiency can be more than 90%. It should be noted that you may have some knowledge about photocatalysts and photocatalysis, and you may have read many reports. One value that should not be ignored is the action time. Some manufacturers do tests, can do more than 99% of the photocatalyst, but the action time is more than 24 hours, even up to 48 hours or 72 hours, the efficiency will be very low.

Since then, we have conducted tests on other harmful gases, such as tribenzene harmful gases, including toluene, xylene, etc., and the typical odor gases, including ammonia, sulfur dioxide, hydrogen sulfide, etc., have a relatively solid experimental basis and experimental data support for photocatalytic materials to remove industrial waste gas and deodorization. Some tests have also been done on bacteria, and the results are also very good.

The mass production equipment structure is very simple, made of equipment, for Staphylococcus albus, H3N2 influenza virus killing efficiency is relatively high.

Structure of photocatalytic air treatment equipment

Three, the existing UV sterilization technology comparison

In the ultraviolet part, there are actually two reactions: ultraviolet photolysis and ultraviolet photolysis. Because the shorter the wavelength and the higher the frequency of ultraviolet light, the greater the energy brought by the light wave itself. Once this energy exceeds the energy between organic matter or compound or cell bond itself, certain photolysis effect will be produced.

The UVC band of ultraviolet mercury lamp is mainly concentrated in 254nm and 185nm, because the mercury source can only excite these two wavelengths with relatively high peaks. At 185nm band, the photolysis effect of ultraviolet mercury and photoozonation effect will appear, so when sterilization with 185nm ultraviolet lamp, photolysis and photoozonation effect related to the bactericidal efficiency of the wavelength of the light source will appear. So it's sometimes difficult to tell whether 185nm mercury lamps are light source sterilization, photolysis sterilization, or photoozone sterilization.

But one thing is certain, the shorter the wavelength, the greater the energy of the light wave, the greater the attenuation efficiency, so the effect of the long distance will be weaker.

UV purification technology comparison

Fourth, UVA LED photocatalytic market application

UV LED has brought great technical advantages to photocatalysis, from the energy intensity and energy density has improved by more than one order of magnitude, unit area has reached 40 to 50 milliwatts per square centimeter without any problems.

Technical advantages of UVA-LED for photocatalysis

The third generation semiconductor technology of low power high photoelectrical efficiency narrow band UVA LED UV light source photocatalytic technology has many advantages:

Sterilization is widely popular and strong ability, no drug resistance, decomposition thoroughly; The thorough mineralization of toxic organic matter can be efficiently degraded; High efficiency, long life; Simple maintenance, running cost bottom; No pollution, non-toxic, health safety, environmental friendly.

Analysis of empty market demand

According to experience, we can divide the empty market into civil, commercial, medical, industrial, military and other big industries. Different application scenarios have different purification requirements. Many existing solutions and technologies are unable to solve the problem. You can refer to your own experience.

In general, the ultraviolet light source based on the third generation semiconductor material brings a new revolution to the whole photocatalysis technology. For example, an order of magnitude increase in the energy of the light source; Life, environmental safety performance has been a qualitative leap; It brings a new opportunity for the research and application of photocatalysis. Leveraging the huge industrial market of environmental protection, general health and virus prevention; The elimination of backward materials and technologies (mercury, activated carbon, etc.) has brought a solid technical foundation.

Application of photocatalytic technology

Guangdong Yueneng Jing Environmental Protection Technology Co., LTD

The company has fully independent intellectual property rights, research and development and preparation of new environmental protection materials, design and manufacture of new environmental protection equipment of high-tech environmental protection enterprises. And was recommended by the third generation semiconductor Alliance LED the drafting of the "photocatalytic purification UVA LED technology Requirements" industry standard.