What is Zinc Sulfide Photocatalyst?
Zinc Sulfide (ZnS) is a semiconductor material that has recently gained significant attention as a potential photocatalyst. Photocatalysts are substances that harness the energy from light to catalyze a chemical reaction, and therefore play an important role in potential renewable energy solutions such as solar power.
In this respect, ZnS shows considerable promise due to its unique optical and electronic properties. This includes a wide band gap energy that allows it to absorb a significant quantity of the solar spectrum, as well as good thermal stability and high sensitivity to light.
Importantly, ZnS is environmentally friendly and abundant, making it a cheaper and more sustainable option compared to some other photocatalysts. It has been applied in various fields such as photocatalytic degradation of pollutants, hydrogen generation by water splitting, CO2 reduction, and sensors. However, the relatively fast recombination rate of photo-generated electron-hole pairs in ZnS needs to be further researched for its optimal utilization.
Why ZnS is Used as a Photocatalyst?
Zinc sulfide (ZnS) is used as a photocatalyst due to its unique properties. ZnS has a wide bandgap and strong photo-absorption capability, making it sensitive to both visible and UV light. As a photocatalyst, it can facilitate chemical reactions upon absorbing light without being consumed or undergoing any permanent chemical change. This makes it suitable for use in various applications like water treatment, air purification, self-cleaning surfaces, and solar energy conversion. Moreover, ZnS is environmentally friendly and non-toxic, which makes it a preferable choice over other materials.
What is the Photocatalytic Activity of ZnS?
ZnS is known for its photocatalytic activity which refers to its ability to absorb light and then use that energy to initiate chemical reactions. It is particularly effective in the ultraviolet range, where it can absorb the light and use it to break down organic compounds or pollutants.
It has been studied for its potential uses in environmental cleanup, specifically for the degradation of organic pollutants, bacteria killing, and even for photocatalytic hydrogen production from water.
However, the photocatalytic activity of ZnS is hampered by its fast recombination of photoinduced electron-hole pairs. To improve the photocatalytic efficiency, modifications are usually needed, such as doping with other elements, creating composites with other materials, or creating specific nanostructures.
It's important to note that photocatalytic activity can vary based on several factors such as particle size, crystalline structure, and the presence of impurities or defects. Therefore, the photocatalytic performance of ZnS can vary significantly depending on its synthesis method and treatment.
What are the Synthesis Methods of Zinc Sulfide Photocatalyst?
ZnS photocatalysts, due to their excellent photocatalytic activity and stability, have aroused widespread interest in the field of environmental protection. Here is a brief description of various synthesis methods of ZnS photocatalyst:
1. Hydrothermal Synthesis Method: This is a common method to synthesize ZnS photocatalyst. It involves autoclaving a solution containing zinc salt and sulfide at a certain temperature.
2. Precipitation Method: This method involves precipitation of Zn2+ and S2- salts in an aqueous solution to form ZnS precipitates. The precipitates are then calcined to form ZnS photocatalysts.
3. Solvothermal Synthesis Method: This method uses a solvent under high temperature and pressure. It helps in synthesizing high purity ZnS nanocrystals. The size and shape of the particles can be easily controlled by altering the temperature, reaction time, or types of solvents.
4. Microwave-assisted Hydrothermal Method: In this method, the microwave radiation is used to accelerate the reaction. This enables the synthesis of ZnS nanocrystals in a shorter time and at a lower temperature as compared to conventional methods.
5. Sol-gel Method: In this process, a gel-like precursor is prepared by dissolving zinc salts in a suitable solvent and then adding a sulfur source. After aging, drying, and calcining steps, ZnS photocatalyst is formed.
All these methods have their own advantages and disadvantages; the choice of method would depend on the specific requirements like particle size and shape, purity, and yield.
Reference
- Lin, M.H.; et al. The study of near-band-edge property in oxygen-incorporated ZnS for acting as an efficient crystal photocatalyst. ACS omega 3.6 (2018): 6351-6359.
