#nitrogen oxides

An improved wearable, stretchable gas sensor using nanocomposites

A stretchable, wearable gas sensor for environmental sensing has been developed and tested by researchers at Penn State, Northeastern University and five universities in China.

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The sensor combines a newly developed laser-induced graphene foam material with a unique form of molybdenum disulfide and reduced-graphene oxide nanocomposites. The researchers were interested in seeing how different morphologies, or shapes, of the gas-sensitive nanocomposites affect the sensitivity of the material to detecting nitrogen dioxide molecules at very low concentration. To change the morphology, they packed a container with very finely ground salt crystals.

Image - Matt Buck, flickr

A Freedom of Information request has shown that the UK government does not know the level of emissions from diesel trains.

The Press Association asked the Department for Transport for figures detailing the annual output of nitrogen oxides, but was told the information was not available.

Approximately 29% of the UK’s train fleet is diesel, although Rail Minister Jo Johnson has unveiled plans for all diesel-only trains to be phased out by 2040.

Speaking in February, Johnson said, ‘If that seems like an ambitious goal, it should be and I make no apology for that. After all, we’re committed to ending the sales of petrol and diesel cars by 2040. If we can achieve that, then why can’t the railway aspire to a similar objective?

‘I am calling on the railway to provide a vision for how it will decarbonise. And I expect the industry to report back by the autumn.’

Successive governments have attempted to electrify more track, but this can be expensive. In March, the National Audit Office released a report outlining how the cancellation of the electrification of the Midland mainline was for financial reasons.

Trolleybuses and Urban Pollution

I reported on MP John Redwood’s thoughts on controlling urban pollution on the 20th April.  In recent years, many cities have returned to the previously old fashioned idea of electric trams.  These are good, but have the disadvantage that they need a lot of disruptive and expensive infrastructure.  The city of Nottingham is an excellent example of this.

Another “old fashioned” approach is the trolleybus, which does not need rails and hence is much cheaper and easier to install.  The first of the pictures above shows a London trolleybus before the system was finally withdrawn in 1962.  I remember riding on them.  They were very quiet and virtually free of pollution at the place of operation. 

Each vehicle had a crew of two: the driver and the conductor.  The latter was responsible for collecting fares, public safety and replacing the electric connection when it fell off the wires, which was a frequent occurence.  They were therefore equipped with a very long pole and it could take several minutes to reconnect the electric supply with this pole.

I was going to conclude that, if this problem could be solved, the trolleybus would be a major part of the answer to urban pollution.  However, on searching for photographs, I found several modern versions, including one from Naples (please see the second picture above).  If you have any experience of modern trolleybuses, please share them here.

A Bochum-based team has developed a new process for zinc oxide layers that can be used for nitrogen oxide sensors as well as protection layer on plastic.

The application of zinc oxide layers in industry is manifold and ranges from the protection of degradable goods to the detection of toxic nitrogen oxide gas. Such layers can be deposited by atomic layer deposition (ALD) which employs typically chemical compounds, or simply precursors, which ignite immediately upon contact with air, i.e. are highly pyrophoric. An interdisciplinary research team at Ruhr-Universität Bochum (RUB) has now established a new fabrication process based on a non-pyrophoric zinc precursor that can be processed at temperatures low enough to allow plastics to be coated. The team published their report in the journal "Small," where it was featured as the cover story in the edition from 4 June 2020.

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Depositing ultra-thin layers

In order to produce a sensor for nitrogen dioxide (NO2), a thin layer of nanostructured zinc oxide (ZnO) must be applied to a sensor substrate and then integrated into an electrical component. Professor Anjana Devi's team used ALD to apply ultra-thin ZnO layers on such sensor substrates.

Used in an Internal combustion engine, the heat of hydrogen combustion will still produce nitrogen oxides, yes?

Yes, it can. Hydrogen internal combustion engines are designed to have near zero emissions, but they cannot be eliminated completely. There are mechanisms to reduce NOx emissions, such as exhaust gas recirculation, but I’m not sure how effective they are.

Excerpt from this New York Times story:

A rule proposed by the Environmental Protection Agency on Friday could better protect communities against pollution from natural gas plants.

For the first time in almost two decades, the rule would update emission limits of nitrogen oxides, a group of gases that are harmful air pollutants produced from burning fossil fuels. The emissions can contribute to asthma and respiratory infections, especially in children, older people and those who are immunocompromised.

“These stronger standards are necessary to better protect nearby communities’ health, and the power sector has already shown that the additional pollution controls can affordably and reliably do the job,” said Joseph Goffman, the E.P.A.’s assistant administrator for air and radiation, in a statement.

The proposal was created to limit nitrogen oxide emissions from all new turbines built at power plants and industrial facilities, along with any existing turbines that are modified or reconstructed after the proposal takes effect.

The stricter standards could also lead to reductions in other types of pollution, like particulate matter and ozone, by lowering the amount available to react with other volatile organic compounds.

“Ultimately, the healthiest option for families across the nation is for power plants to stop burning fossil fuels altogether and for utilities to invest in clean and reliable renewable energy,” said Holly Bender, the Sierra Club’s chief energy officer, in a statement.

Ozone (O3) is a molecule made up of three atoms of oxygen (O), and is mostly found in the stratosphere, where it protects us from the Sun’s harmful ultraviolet (UV) radiation. Although it represents only a tiny fraction of the atmosphere, ozone is crucial for life on Earth. Ozone in the stratosphere—a layer of the atmosphere between 15 and 50 kilometers (10 and 31 miles) above us—acts as a shield to protect Earth’s surface from the sun’s harmful ultraviolet radiation. Without ozone, the Sun’s intense UV radiation would sterilize the Earth’s surface.