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Lampshades Gain New Purpose as Indoor Air Purifiers Thanks to New Catalyst Coating

A close-up photo of a lit lamp and lampshade.
Credit: Minhyung Lee / Yonsei University.
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Researchers have developed a new catalyst coating for lampshades that can take the heat generated by lightbulbs and use it to break down harmful indoor air pollutants. The research was presented at the fall meeting of the American Chemical Society (ACS), held online and in person in San Francisco, California.

Sources of indoor air pollution

Away from vehicle exhaust fumes and clouds of pollen, you might think that the air indoors is beautifully clear, crisp and free of pollutants. But just because the pollution isn’t noticeable to our eyes and noses, that doesn’t mean that it isn’t there. 

Secondhand smoke, wood-burning heaters and incense can all lead to an increased concentration of particulate matter in the air that we breathe indoors. But many of the most important indoor air pollutants are airborne chemicals, also known as volatile organic compounds (VOCs).

VOCs are found in many everyday products, including air fresheners, spray deodorants, cleaning products and paints. Exposure to these VOCs in high amounts can cause eye and airway irritation, headaches and nausea. But even at lower levels, chronic exposure can be problematic. Those with asthma or a similar heightened sensitivity to chemicals, the elderly and the very young can also be more susceptible to irritation from VOCs circulating in the air.

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

The bright idea: using waste lightbulb heat to power a purifier

For those who are concerned about indoor air pollution, commercial air purifiers can be used to remove particulate matter and VOCs from the air. But these devices aren’t perfect.

“Conventional methods to remove VOCs from indoor air rely on activated carbon or other types of filters, which have to be replaced periodically,” said Minhyung Lee, a graduate student in Kim’s lab at Yonsei University.

Other options are based on the use of thermocatalysts, which chemically break down VOCs into different harmless compounds when they are activated by high temperatures, or photocatalysts that do the same when exposed to strong light. These can be an effective solution, but as Kim notes, these units are somewhat limited by the need for a separate heater or ultraviolet (UV) light source, which could cause further problems with unwanted byproducts down the road.

To find a way around this problem, Kim and colleagues began experimenting with simpler approaches. By exploiting the inefficiencies of halogen and incandescent bulbs – which convert only around 510% of the power they use into light, with the rest being emitted as heat – the researchers saw an opportunity to seamlessly integrate thermocatalyst-based air purifiers into the home. 

In a paper published last fall, the researchers demonstrated a proof-of-concept lampshade internally coated with thermocatalysts synthesized from titanium dioxide and small amounts of platinum. The lampshade was tested with a 100-watt halogen bulb in a test chamber containing air and acetaldehyde gas – a common VOC pollutant. Turning on the lamp quickly heated the shade to temperatures of around 250 °F, hot enough for the lampshade’s thermocatalyst layer to begin to break down the gaseous VOC.

“That heat is typically wasted, but we decided to use it to activate a thermocatalyst to decompose VOCs,” Kim said. “This was the first demonstration to utilize waste heat from lamp sources.”

Specifically, the lampshade was able to convert the acetaldehyde in the test chamber to acetic acid, then into formic acid and finally into carbon dioxide and water. Both of these acids are much milder than acetaldehyde, Kim says, with the small amounts of carbon dioxide also being harmless.

Building more practical thermocatalysts

After this successful demonstration, the researchers set about investigating ways to make their lampshade air purifiers more viable for general use.

In their new research, presented at ACS Fall 2023, the researchers report the development of new iron- and copper-based catalysts that can similarly break down VOCs without the need for expensive platinum additives.

The development of such a copper-based thermocatalyst that can be mounted inside of a lampshade for indoor use is particularly exciting, the researchers say, as copper is a natural disinfectant. This allows the lampshade air purifier to have dual-action, killing off airborne microorganisms through the copper’s anti-microbial properties as well as transforming dangerous VOCs into less harmful compounds.

Building on these discoveries, Kim said that the research group’s new focus is searching for similar materials that will enable this design to be used for LED bulbs – a more efficient type of lightbulb that wastes less energy to heat and is becoming increasingly popular. For this, they are developing photocatalysts that respond to the near-UV light that is emitted by white and daylight LED lightbulbs. Additionally, they are searching for more novel catalysts that might be capable of absorbing the light produced by lightbulbs and converting it into heat energy to activate a thermocatalyst. 

“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 said.

Reference: Lee M. Thermocatalytic oxidation of VOC through harnessing indoor waste heat. Presented as part of ACS Fall 2023; August 16, 2023; San Francisco, CA.

This article is based on research findings that are yet to be peer-reviewed. Results are therefore regarded as preliminary and should be interpreted as such. Find out about the role of the peer review process in research here. For further information, please contact the cited source.

This article is a rework of a press release issued by the American Chemical Society. Material has been edited for length and content.