Probing the Possibilities: Advancing Photocatalyst Applications

Photocatalyst is a general term for semiconductor materials with photocatalytic function represented by nano-scale titanium dioxide. The representative photocatalyst material is titanium dioxide, which can produce strong oxidizing substances under light irradiation, and can be used to decompose organic compounds, some inorganic compounds, bacteria and viruses.

Photocatalyst Materials

The commonly used photocatalyst semiconductor materials are titanium dioxide. ZrO₂, ZnO, CdS, WO₃, Fe₂O₃, PbS, SnO₂, ZnS, SrTiO₃, and SiO₂ are also photocatalyst materials. Since 2000, it has been found that some nano-noble metals (platinum, rhodium, palladium, etc.) have better photocatalytic properties.

Research Findings of Photocatalysts

Photocatalyst materials based on zinc oxide have been discovered as early as the 1930s. In 1967, Akira Fujishima, a graduate student of the University of Tokyo working under the guidance of Associate Professor Kenichi Honda, discovered that the electrolysis of water could be carried out by irradiating titanium dioxide electrodes with light, that is, the "Honda-Fujishima Effect",  which opened the door to the application of titanium dioxide in the field of photocatalysis. In 1972, Nature published Fujishima and Honda's research on photocatalysis in the field of photolysis of water, which opened a new chapter in photocatalysis research.

In 1976, Garey et al. pioneered the application of photocatalysts in the field of environmental protection, using photocatalysis to degrade pollutants in water. Since then, expanding the application field of semiconductor photocatalyst materials in life sciences and converting light energy into other energies has become the main research direction.

In 2015, a Japanese company developed a new type of photocatalyst particle, which is expected to solve the problem of water shortage. The particles are composed of zeolite particles and titanium dioxide particles, which are fully mixed in the sewage under ultraviolet irradiation, so that the sewage can be purified to a drinkable level. The new photocatalyst water purification equipment is quite simple and efficient, and can purify up to 3 tons of water a day. Efficient and clean photocatalyst materials have attracted people's attention in the era of energy saving.

Efficacy and Application of Photocatalysts

Air purification

The photocatalyst generates hydroxyl radicals after being exposed to light, and reacts with organic substances in the air to form non-toxic inorganic substances, which can effectively decompose formaldehyde, benzene, ammonia, convert them into H₂O and CO₂, and oxidize and remove ammonia nitrogen compounds, sulfides and various odors in the atmosphere, and play the role of air purification. Experimental studies have shown that the degradation of air pollutants by photocatalysts is related to their concentration. Formaldehyde at low concentrations can be completely decomposed into H₂O and CO₂ by photocatalysts, while at higher concentrations, it is first oxidized into intermediates such as HCOOH, and then in decomposed into H₂O and CO₂.

Antibacterial material

The photocatalyst sol is coated on the surface of building tiles by pulling, spinning, spraying, smearing, and then baked to form a solid photocatalyst film on the surface of the tiles. This photocatalytic tile has the functions of decomposing oil stains, sterilizing bacteria, and can be used on the walls of kitchens and bathrooms. Experimental test results show that the number of bacteria survival on antibacterial ceramic products is less than 1% of that of ordinary ceramic products. This antibacterial effect can effectively prevent the reproduction and growth of bacteria on dark, damp, and difficult-to-clean sanitary ware, and can prevent urine scaling and foul odors, and has great market potential.

Wastewater treatment

Under the condition of light, the photocatalyst can make the hydroxyl, halogenated, carboxylic acid and other substances in the water undergo redox reaction and gradually degrade, and finally become harmless small molecular substances. Under sunlight irradiation, the removal efficiency of olive oil wastewater treated with nano-TiO₂-loaded sepiolite reached 80%.

Anti-ultraviolet products

Nano-photocatalyst has a strong ability to scatter and absorb ultraviolet rays, and convert this light energy into chemical energy, so it has the functions of anti-ultraviolet and preventing fading and aging. TiO₂ photocatalyst, especially the harmful mid- and long-wave ultraviolet rays, has a strong absorption ability, and can pass through visible light. It is non-toxic, tasteless, and non-irritating. In addition, it can be colored at will and is cheap. Therefore, it is widely used in sunscreen cosmetics.

Disease treatment

The latest application of photocatalysis is for disease treatment, and the photocatalytic mosquito trap developed by Akira Fujishima has already been used in areas where malaria is rampant.

Alfa chemistry is a reputable provider of diverse photocatalysts, including acridines catalyst, carbazoles catalyst, iridium catalyst, and ruthenium catalyst, that are essential for efficient and sustainable chemical reactions in various research and industrial applications.