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Air pollution is becoming a growing worldwide issue, as pressures to tackle emissions build and scientists find more evidence of the negative impact of various atmospheric molecules on human and environmental health.
To tackle this problem, a group of scientists working under the Graphene Flagship initiative has developed a graphene-based photocatalyst that they have proven to be effective at downgrading at least 70% more nitrogen oxide (NOx) than current methods can achieve. It is thought that this innovation will be key to reducing air pollution by lowering levels of NOx that is added to the atmosphere by burning fossil fuels.
Titania nanoparticles are currently used in coatings to help reduce atmospheric nitrogen oxides. However, the new approach that uses a graphene titania photocatalyst will vastly improve the impact of these coatings on reducing the greenhouse gases that cause global warming.
The Growing Problem of Atmospheric Pollution
Air pollution is being deemed a public health emergency by the World Health Organization (WHO) director, Dr. Maria Neira. It is estimated that air pollution claims the lives of over 7 million people each year. Put into perspective, that is more than the combined deaths attributed to HIV, malaria, and tuberculosis.
As the world’s population grows, and more rural areas are urbanized, the demand for power increases. While governments across the globe are setting goals to switch to clean energy alternatives to stop adding more greenhouse gases into the atmosphere, some of these initiatives will take years to see countries fully adopting clean energy.
In the meantime, the combustion of fossil fuels continues to add harmful gases into the air, with traffic being a major contributor to this kind of pollution. Nitrogen oxides, along with volatile compounds, are the main cause of air pollution-related deaths, which currently account for around one in nine mortalities.
Technology is being called upon to address this problem. For a number of years, researchers have dedicated themselves to exploring new ways to safely remove harmful pollutants from the atmosphere, giving people cleaner air to breathe.
Graphene’s Role in Clean Energy
Back in 2004, scientists at the University of Manchester discovered and isolated graphene for the first time. Graphene is a single layer of graphite, an allotrope of carbon, that is just one atom thick. It was the first two-dimensional material to be discovered, and because of this, as well as its unique and impressive qualities of being extremely thin, incredibly strong, flexible, and an excellent thermal conductor with high chemical stability, research into potential applications of the material subsequently boomed.
Clean energy is just one of the numerous fields that have already greatly benefited from developments using graphene. Its properties already make it highly suitable for use in next-generation electronics. This has inspired scientists to investigate how graphene can be used in new, clean technologies.
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Graphene is being used successfully in new solar panels, making them ultra-thin and flexible, and most importantly, highly efficient. Graphene membranes have been created to artificially mimic photosynthesis by conducting protons when illuminated by sunlight, harvesting solar energy to create hydrogen.
Recent research has also revealed that graphene’s hexagonal atomic structure makes it ideal for filtering atoms, meaning it could have an application in preventing greenhouse gases from being added into the atmosphere by processes that rely on combustion.
A team at MIT recently published a paper describing how graphene can be added into photovoltaic cells to convert power at higher efficiencies than current technologies.
Graphene is being looked to again to create a composite material for use as a coating with the aim of downgrading atmospheric nitrogen oxide.
What is the Graphene Flagship Project?
Graphene Flagship is a partnership between teams at the University of Bologna, the University of Cambridge, CNR, Eindhoven University of Technology, Politecnico di Milano, the Israel Institute of Technology, Italcementi HeidelbergCement Group, and NEST.
In a paper published in the journal Materials Today: Proceedings, the team discusses how a graphene-titania composite material was created that is proven to be more efficient in conducting the process of photodegradation in comparison with bare titania.
Titania is the most commonly used photocatalytic material. It has long been used to create composite materials with photocatalytic properties. Increasingly, photocatalysis is being focused on as a method of reversing the negative impact of human activity on the environment by reducing the volume of greenhouse gases in the atmosphere.
The process does not use up the photocatalysts and is activated by solar energy, making it a viable solution to reducing greenhouse gas emissions in the long-term.
Developing a Graphene Titania Photocatalyst
To produce the coating with enhanced photocatalytic properties, the team developed a graphene-titania nanocomposite. The researchers created graphene via the process of liquid-phase exfoliation of graphite, which they did in the presence of nanoparticles of titania, and in the absence of any other materials apart from water.
This process formed a new graphene-titania nanocomposite. The team then used this to create a coating that can be added onto the surface of various materials, resulting in the passive photodegradation of air pollutants.
The idea is to paint buildings with the coating, where the nanocomposite could work on breaking down the high levels of emissions in city atmospheres. The products of the photodegradation process then sit on the building’s surface until they are naturally washed away by wind or rain.
In testing the new photocatalyst, the team found it to be successful at downgrading 70% more NOx and 40% more rhodamine B (used as a model for volatile organic pollutants) than current photocatalytic coatings.
Future Impact of Graphene on Climate Change
The team witnessed excellent results of the graphene titania photocatalyst in powder form. It is predicted that the powder could be easily applied to a variety of composite materials, including concrete. If this new form of concrete were to see widespread adoption, then the levels of emissions could be significantly reduced, helping to limit the detrimental impact of climate change.
The construction industry could be significantly influenced in the future by innovations such as those developed by the Graphene Flagship Project and others as the pressure to combat emissions increases. In addition, the graphene industry will continue to be fueled by its growing list of applications in clean technology and more.
References and Further Reading
A graphene coating on buildings could reduce air pollution. Air Quality News. Pippa Neill. https://airqualitynews.com/2019/12/09/a-graphene-coating-on-buildings-could-reduce-air-pollution/
Air pollution: everything you should know about a public health emergency. The Guardian. Damian Carrington. https://www.theguardian.com/environment/2018/nov/05/air-pollution-everything-you-should-know-about-a-public-health-emergency
Environmental applications of titania-graphene photocatalysts. Science Direct. Marisol Faraldos, Ana Bahamonde. https://www.sciencedirect.com/science/article/abs/pii/S0920586117300299
Photocatalytic activity of exfoliated graphite-TiO2 nanoparticle composites. Nanoscale. Gloria Guidetti, Eva Pogna, Lucia Lombardi. https://pubs.rsc.org/en/content/articlelanding/2019/nr/c9nr06760d/unauth#!divAbstract
Photocatalytic Activity of Graphene – Titania Nanocomposite. Materials Today: Proceedings. A.K. Akhila, P.S. Vinitha, N.K. Renuka. https://www.sciencedirect.com/science/article/pii/S2214785318310460
Proton transport in graphene shows promise for renewable energy. Phys.org. University of Manchester. https://phys.org/news/2018-01-proton-graphene-renewable-energy.html
Smog-eating graphene composite reduces atmospheric pollution. Graphene Flagship. https://graphene-flagship.eu/news/press/Pages/Press.aspx#/news/smog-eating-graphene-composite-reduces-atmospheric-pollution-388860