Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - nanoPhotoMat (Development of nano-Photocatalytic Materials for Indoor Air Purification and Odour Elimination)

Teaser

Air pollutants severely affect people’s life quality and life expectancy. Long time exposure to air pollution causes serious health problems, such as heart diseases, cancer, asthma, allergy, irritation and lost productivity. Indoor air contaminants arise from both outside...

Summary

Air pollutants severely affect people’s life quality and life expectancy. Long time exposure to air pollution causes serious health problems, such as heart diseases, cancer, asthma, allergy, irritation and lost productivity. Indoor air contaminants arise from both outside and indoor sources. Indoor volatile organic components (iVOCs) that were generated each time household and cleaning products are used, continuously accumulated inside due to poor ventilation. Considering we typically spend 90% of our time at interior places, we are faced with a serious problem in our daily life. So, it has been crucially important that recent technological advances should bring innovative solutions to eliminate the indoor air pollutants as well as odour riddance.
Our aim is to develop an air purifier for which elimination of the indoor volatile organic compounds (iVOCs) is the main purpose. There are several air purifiers available in the global consumer market, but only a few of them are able to mineralize VOCs. The ones which implemented photocatalytic oxidation (PCO) technology are promoted generation of ozone and led to release of by-products which are more hazardous than the initial reactants.
In this project, we studied the PCO technology with the purpose of understanding the degradation mechanisms of iVOCs and we worked on optimization of the system towards preventing the release of hazardous by-products.
- The main objective of this study was to develop an air purifier with PCO technology where indoor VOCs degraded to water and carbon dioxide.
- The state-of-the-art synthesis of well-developed mesoporous TiO2-based photocatalysts with specific structural properties, such as high surface area (106 m²/g) and large pore volume (0.2 cm³/g) was achieved.
- By doping TiO2 nanoparticles with a cheap earth metal, Fe, we could prepare visible-light active photocatalytic materials instead of conventional UV-active photocatalytic materials.
- Low-power and eco-friendly (ozone free) light sources were selected to activate the photocatalytic materials at visible region.
- Different configurations for PCO system were examined to provide uniform air flow and effective illumination over catalyst surfaces.
- We investigated the reaction mechanisms of different types of chemicals (aliphatics, aromatics etc.) on two different crystal surfaces of anatase TiO2 that were An(101) and An(001),
- We derived PCO reaction pathways for formaldehyde, and benzene oxidation with the help of DFT studies. Reaction enthalpies and activation barriers of the each reaction steps were calculated.
- Performance tests of the PCO units were conducted at room conditions where the suppressing effect of high humidity on PCO reaction was observed.

Work performed

The main objective of this project was to develop the next generation air purifiers, in which PCO technology would allow elimination of a variety of hazardous indoor air pollutants, and bad odour caused by such pollutants, when illuminated by low-power light sources on-the-fly. To achieve our goal, we worked on the development of more ordered and interconnected photocatalytic materials, and therefore, we synthesized the photocatalytic element in-house and operate them under visible light. The main outcomes of this study were:
• A new chemistry laboratory was set up at Arçelik Central R&D facilities for the synthesis of photocatalytic materials and also for the performance tests of both benchmarks and home-made air purification systems.
• We developed mesoporous pure anatase TiO2-based materials with high surface area and large pore volume in powder form.
• Sol of photocatalytic materials could be successfully coated on quartz surfaces.
• The synthesis materials were able to absorb visible light between 400 and 800 nm.
• In plate-like reactor design, uniform air flow distribution and effective illumination could be sustained which led to effective use of catalyst surfaces during PCO reaction.
• Visible light sources (0.1-1.4 W/m2) had very low irradiance power compared to UV light sources (270 W/m2).
• Formaldehyde could be easily degraded to CO2 and H2O on anatase TiO2 surfaces in both experimental studies and theoretical DFT calculations.
• We showed that formaldehyde combustion was more favourable on An(101) TiO2 than An(001).
• Apparent barrier between the reaction steps of cyclic structure of formaldehyde (-CH2-O-) and water adsorption became lower when Fe was doped on TiO2. Moreover, the whole combustion cycle stayed at exothermic region in case of Fe/TiO2 An(001).
• Degradation of aromatic rings (benzene and toluene) was slower than aliphatics (i.e. n-hexane) on anatase TiO2 surfaces.
• Experimentally, benzene degradation was more difficult than toluene on anatase TiO2.
• We proved with DFT studies that both adsorption and the ring opening reactions of benzene on anatase TiO2 surfaces was very difficult. This might be the reason for the slower conversion of benzene than toluene in experimental studies.
• We predicted that although benzene could be adsorbed on the TiO2 anatase surfaces, it was probably very easily desorbed either being benzene molecule or most probably forming phenol.
In this project, we established a collaboration with Dr. Olus Ozbek from Yeditepe University to investigate the formation of intermediate products of PCO reaction, to derive reaction pathways and to calculate the energy required to overcome the activation barriers of rate-determining steps.

Dissemination of the project:
I took part in a twitter chat on 4th of July 2017. The event organized by MSCA Team. I answered the questions of the researchers, who were interested and keen to apply for MSCA-IF grant in the Society & Enterprise panel.
I made a presentation at my former university (Middle East Technical University) to around 60 B.Sc. students. I talked about my career path and experiences gained till now, and explained the scope of my MSCA project and the planned studies for the short- and long- term.
I joined to an interview for the Horizon Magazine and we talked about the effect of air pollution to human health and how we looked at the problem towards bringing a viable solution. The article can be tracked from the link: https://horizon-magazine.eu/article/artificial-forest-air-and-light-based-chemical-reactions-tackle-indoor-pollution.html

Final results

We aimed by this project to develop an energy efficient and environmental-friendly air purifier prototype where indoor volatile organic components could be eliminated by PCO technology. Beyond that, it is in our knowledge that air pollution is not only caused by the release of VOCs, but there are also other factors to be considered, such as particulate matters with different sizes and types, and inorganic gases at elevated concentrations. Therefore, Arçelik Company Central R&D division conducts several other projects on air purification, which are initiated in the course of my project by benefiting from the outcomes of this research. I believe that the outcomes of all these work will bring a big social impact because each of us deserves to breathe clean air at any time of the day regardless of the location. Although we targeted developing an air purifier for a room-size (ca. 30 m3) places, the technology can be much easily used on a bigger scale than a room-size application, for example as a residential air purification system for supplying clean air to multiple buildings.

Website & more info

More info: http://www.arcelikglobal.com/en/.