08-16-2023

Special coating transforms a lampshade into an air purifier

Earth.com staff writer

Indoor air pollution has found a new adversary: a team of scientists led by Yonsei University has recently developed lampshades coated with a special catalyst that can convert harmful indoor air contaminants into innocuous compounds.

This technology works both with halogen and incandescent lamps, and efforts are in progress to make it compatible with LED lights as well.

Volatile organic compounds

The innovation primarily focuses on volatile organic compounds (VOCs) – the major culprits behind indoor air pollution, encompassing substances like acetaldehyde and formaldehyde, which emanate from sources such as paints, cleaning agents, air refreshers, plastics, furniture, and even during cooking.

“Although the concentration of VOCs in a home or office is low, people spend more than 90 percent of their time indoors, so the exposure adds up over time,” said principal investigator Hyoung-il Kim, an expert in Civil and Environmental Engineering at Yonsei.

“Conventional methods to remove VOCs from indoor air rely on activated carbon or other types of filters, which have to be replaced periodically,” added Minhyung Lee, a postgraduate researcher from Kim’s team.

A simpler solution

According to Lee, there are other devices that eradicate VOCs using thermocatalysts activated by heightened temperatures or photocatalysts sensitive to light. However, the majority of these devices need either an additional heating unit or ultraviolet (UV) light, both of which could introduce undesirable byproducts.

By contrast, the new technique uses just a regular visible light source that also emanates heat – such as a halogen or incandescent light – complemented by a lampshade infused with a thermocatalyst.

Halogen lamps transform only about 10 percent of the consumed energy into light, while the rest becomes heat. Incandescent bulbs fare even lower, emitting five percent light and 95 percent heat. “That heat is typically wasted, but we decided to use it to activate a thermocatalyst to decompose VOCs,” Kim explained.

How it works

Last year, the scientists formulated thermocatalysts using titanium dioxide supplemented with a small amount of platinum and applied them to an aluminum lampshade’s inner surface, which was then positioned over a 100-watt halogen bulb in an experimental setting with air and acetaldehyde gas.

Upon switching the light on, the lampshade’s temperature rose to around 250 degrees Fahrenheit, sufficient to trigger the catalysts and break down acetaldehyde.

During this oxidation process, the VOC was initially converted into acetic acid, then into formic acid, and ultimately into harmless carbon dioxide and water. The experts also discovered that formaldehyde can be decomposed under the same conditions and that the technique works with incandescent bulbs.

“This was the first demonstration to utilize waste heat from lamp sources,” Kim said. Earlier studies and even a few market-available lamps largely depended on photocatalysts activated by light to combat indoor air pollution.

Future research

Venturing further, Kim and his team are exploring cost-effective alternatives to platinum. Preliminary results suggest that iron or copper-based catalysts can be effective against VOCs. Given that copper possesses disinfectant properties, Kim is optimistic about its potential to neutralize airborne germs.

Now, the challenge is to expand this revolutionary lampshade concept to LEDs, which are a fast-growing segment of the lighting industry. However, unlike their halogen and incandescent counterparts, LEDs do not produce sufficient heat to trigger thermocatalysts.

Hence, Kim’s group is now working on creating photocatalysts responsive to the near-UV radiation from LEDs, along with other catalysts that can convert some of the LEDs’ visible light into heat.

“Our ultimate goal is to develop a hybrid catalyst that can utilize the full spectrum produced by light sources, including UV and visible light, as well as waste heat,” Kim concluded.

This study was presented at the American Chemical Society (ACS) Fall 2023 convention (August 13-17).

More about VOCs

VOCs, or Volatile Organic Compounds, are chemicals that evaporate easily at room temperature. They’re found in many everyday products like paints, cleaning agents, and even some cosmetics.

When released into the air, they can cause health issues and contribute to smog and pollution. It’s a good idea to use products with low or no VOCs and ensure proper ventilation when using products that might contain them.

Short-term exposure can lead to: