Nav: Home

Ammonia by phosphorus catalysis

January 16, 2019

More than 100 years after the introduction of the Haber-Bosch process, scientists continue to search for alternative ammonia production routes that are less energy demanding. Chinese scientists have now discovered that black phosphorus is an excellent catalyst for the electroreduction of nitrogen to ammonia. According to their study published in the journal Angewandte Chemie, layered black phosphorus nanosheets are a highly selective and efficient catalyst in this process.

Ammonia is an essential raw material in all industrial areas, from agriculture to fine chemicals and the pharmaceutical industry. For more than a century, it has been synthesized industrially by the Haber-Bosch process, in which nitrogen from air is reduced with hydrogen or synthesis gas under high pressure and temperature over a transition-metal catalyst. However, the energy demand of this process is so high that one to two percent of the global energy supply is devoted to industrial production of ammonia.

Researchers are in search of milder alternatives, which employ catalysts that operate under ambient conditions. Metal-free alternatives are especially desirable. A highly interesting candidate is phosphorus in its lowest reactivity, nontoxic form: black phosphorus. This material is a rising star in electronic applications because of its metallic-like appearance and unusual electronic properties. Moreover, its puckered two-dimensional sheet-like structure may provide the necessary edges and sites for adsorption and molecular activation.

With this idea in mind, researcher Haihui Wang at the South China University of Technology, Guangzhou, China, and colleagues, prepared thin layers of bulk black phosphorus, "by a facile liquid exfoliation method," as stated in their publication. The catalyst nanosheets were included in a carbon fiber electrode for electrolysis. To provide a nitrogen supply, a hydrochloride electrolyte solution was saturated with nitrogen.

On application of a voltage, the electrode readily and selectively produced ammonia from nitrogen, and the layered black phosphorus even outperformed "most nonmetallic and metal-base catalysts reported at present," added the authors. The extraordinary activity and selectivity of this material are explained by the structure and energetics of the phosphorus sheets.

What is so special about phosphorus? With theoretical calculations, the authors found that the zigzag arrangement in the phosphorus layers, in contrast to other layered or flat materials, provided ideal sites for nitrogen adsorption and the electronic structure at the edges was best suited for binding, activating, and reducing nitrogen by a low-energy pathway.

Having explained the extraordinary activity and selectivity of the layered black phosphorus catalyst, the authors admitted that--despite the generally good stability of black phosphorus under ambient conditions--its performance declined in the long term because of oxidation. "Thus, further improvements in preventing black phosphorus degradation in the electrolyte will be beneficial," they concluded.

This work opens up a novel and attractive application for black phosphorus. In electrocatalytic nitrogen reduction, the performance of black phosphorus is superior to other nonmetallic and even metallic catalysts, suggesting that this material may soon play a bigger role in electrocatalysis. In time, perhaps even the Haber-Bosch process will have a competitor.
-end-
About the Author

Prof. Haihui Wang is leader of the Membrane Science and Energy Materials group at the South China University of Technology, Guangzhou, China. The group seeks solutions for current environmental and energy problems through scientific and technological innovation, with a focus on membrane technology and new energy materials.

http://www.scut.hhwang.ycym.com/

Wiley

Related Nitrogen Articles:

'Black nitrogen'
In the periodic table of elements there is one golden rule for carbon, oxygen, and other light elements.
A deep dive into better understanding nitrogen impacts
This special issue presents a selection of 13 papers that advance our understanding of cascading consequences of reactive nitrogen species along their emission, transport, deposition, and the impacts in the atmosphere.
How does an increase in nitrogen application affect grasslands?
The 'PaNDiv' experiment, established by researchers of the University of Bern on a 3000 m2 field site, is the largest biodiversity-ecosystem functioning experiment in Switzerland and aims to better understand how increases in nitrogen affect grasslands.
Reducing reliance on nitrogen fertilizers with biological nitrogen fixation
Crop yields have increased substantially over the past decades, occurring alongside the increasing use of nitrogen fertilizer.
Flushing nitrogen from seawater-based toilets
With about half the world's population living close to the coast, using seawater to flush toilets could be possible with a salt-tolerant bacterium.
We must wake up to devastating impact of nitrogen, say scientists
More than 150 top international scientists are calling on the world to take urgent action on nitrogen pollution, to tackle the widespread harm it is causing to humans, wildlife and the planet.
How nitrogen-fixing bacteria sense iron
New research reveals how nitrogen-fixing bacteria sense iron - an essential but deadly micronutrient.
Corals take control of nitrogen recycling
Corals use sugar from their symbiotic algal partners to control them by recycling nitrogen from their own ammonium waste.
Foraging for nitrogen
As sessile organisms, plants rely on their ability to adapt the development and growth of their roots in response to changing nutrient conditions.
Inert nitrogen forced to react with itself
Direct coupling of two molecules of nitrogen: chemists from Würzburg and Frankfurt have achieved what was thought to be impossible.
More Nitrogen News and Nitrogen Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Meditations on Loneliness
Original broadcast date: April 24, 2020. We're a social species now living in isolation. But loneliness was a problem well before this era of social distancing. This hour, TED speakers explore how we can live and make peace with loneliness. Guests on the show include author and illustrator Jonny Sun, psychologist Susan Pinker, architect Grace Kim, and writer Suleika Jaouad.
Now Playing: Science for the People

#565 The Great Wide Indoors
We're all spending a bit more time indoors this summer than we probably figured. But did you ever stop to think about why the places we live and work as designed the way they are? And how they could be designed better? We're talking with Emily Anthes about her new book "The Great Indoors: The Surprising Science of how Buildings Shape our Behavior, Health and Happiness".
Now Playing: Radiolab

The Third. A TED Talk.
Jad gives a TED talk about his life as a journalist and how Radiolab has evolved over the years. Here's how TED described it:How do you end a story? Host of Radiolab Jad Abumrad tells how his search for an answer led him home to the mountains of Tennessee, where he met an unexpected teacher: Dolly Parton.Jad Nicholas Abumrad is a Lebanese-American radio host, composer and producer. He is the founder of the syndicated public radio program Radiolab, which is broadcast on over 600 radio stations nationwide and is downloaded more than 120 million times a year as a podcast. He also created More Perfect, a podcast that tells the stories behind the Supreme Court's most famous decisions. And most recently, Dolly Parton's America, a nine-episode podcast exploring the life and times of the iconic country music star. Abumrad has received three Peabody Awards and was named a MacArthur Fellow in 2011.