Perovskites are a class of synthetic materials that have a crystalline structure similar to that of the naturally occurring mineral calcium titanate. They have been the subject of many studies because they exhibit exciting and unique properties that can be tuned according to their composition. One of their potential applications is as catalysts for the synthesis of ammonia. In other words, specific perovskites can be placed inside a reaction chamber with nitrogen and hydrogen to promote the reaction of these gases to form ammonia.
Ammonia is a useful substance that can be employed in the production of fertilizers and artificial chemicals, and even as a clean-energy carrier (in the form of hydrogen), which may be key in eco-friendly technologies.
However, there are various challenges associated with the synthesis of ammonia and perovskites themselves.
The synthesis rate for ammonia is generally limited by the high energy required to dissociate nitrogen molecules. Some researchers have had some success using precious metals, such as ruthenium.
Recently, perovskites with some of their oxygen atoms replaced by hydrogen and nitrogen ions have been developed as efficient catalysts for ammonia synthesis. However, the traditional synthesis of perovskites with such substitutions usually has to be carried out at high temperatures (more than 800°C) and over long periods of time (weeks).
To address these issues, in a recent study carried out at Tokyo Tech, a group of researchers led by Prof. Masaaki Kitano devised a novel method for the low-temperature synthesis of one of such oxygen-substituted perovskites with the chemical name BaCeO3?xNyHz and tested its performance as a catalyst to produce ammonia.
To achieve this, they made an innovative alteration to the perovskite synthesis process. The use of Barium carbonate and Cerium dioxide as precursors (or "ingredients") involves a very high temperature would be required to have them combine into the base perovskite, or BaCeO3, because Barium carbonate is very stable.
In addition, one would then have to substitute the oxygen atoms with nitrogen and hydrogen ions. On the other hand, the team found that the compound Barium amide reacts easily with Cerium dioxide under ammonia gas flow to directly form BaCeO3?xNyHz at low temperatures and in less time (Fig. 1). "This is the first demonstration of a bottom-up synthesis of such a material, referred to as perovskite-type oxynitride-hydride," explains Prof. Kitano.
The researchers first analyzed the structure of the perovskite obtained through the proposed process and then tested its catalytic properties for the low-temperature synthesis of ammonia under various conditions.
Not only did the proposed material outperform most of the state-of-the-art competitors when combined with ruthenium, but it also vastly surpassed all of them when combined with cheaper metals, such as cobalt and iron (see Fig. 2). This represents tremendous advantages in terms of both performance and associated cost.
Finally, the researchers attempted to elucidate the mechanisms behind the improved synthesis rate for ammonia. Overall, the insight provided in this study serves as a protocol for the synthesis of other types of materials with nitrogen and hydrogen ion substitutions and for the intelligent design of catalysts.
"Our results will pave the way in new catalyst design strategies for low-temperature ammonia synthesis," concludes Prof. Kitano. These findings will hopefully make the synthesis of useful materials cleaner and more energy efficient.
Kazuhide Hasegawa | EurekAlert!
Tiny quantum sensors watch materials transform under pressure
13.12.2019 | DOE/Lawrence Berkeley National Laboratory
Light, strong, and tough: Researchers at the University of Bayreuth discover unique polymer fibres
13.12.2019 | Universität Bayreuth
Vaccinia viruses serve as a vaccine against human smallpox and as the basis of new cancer therapies. Two studies now provide fascinating insights into their unusual propagation strategy at the atomic level.
For viruses to multiply, they usually need the support of the cells they infect. In many cases, only in their host’s nucleus can they find the machines,...
More than one hundred and fifty years have passed since the publication of James Clerk Maxwell's "A Dynamical Theory of the Electromagnetic Field" (1865). What would our lives be without this publication?
It is difficult to imagine, as this treatise revolutionized our fundamental understanding of electric fields, magnetic fields, and light. The twenty original...
In a joint experimental and theoretical work performed at the Heidelberg Max Planck Institute for Nuclear Physics, an international team of physicists detected for the first time an orbital crossing in the highly charged ion Pr⁹⁺. Optical spectra were recorded employing an electron beam ion trap and analysed with the aid of atomic structure calculations. A proposed nHz-wide transition has been identified and its energy was determined with high precision. Theory predicts a very high sensitivity to new physics and extremely low susceptibility to external perturbations for this “clock line” making it a unique candidate for proposed precision studies.
Laser spectroscopy of neutral atoms and singly charged ions has reached astonishing precision by merit of a chain of technological advances during the past...
The ability to investigate the dynamics of single particle at the nano-scale and femtosecond level remained an unfathomed dream for years. It was not until the dawn of the 21st century that nanotechnology and femtoscience gradually merged together and the first ultrafast microscopy of individual quantum dots (QDs) and molecules was accomplished.
Ultrafast microscopy studies entirely rely on detecting nanoparticles or single molecules with luminescence techniques, which require efficient emitters to...
Graphene, a two-dimensional structure made of carbon, is a material with excellent mechanical, electronic and optical properties. However, it did not seem suitable for magnetic applications. Together with international partners, Empa researchers have now succeeded in synthesizing a unique nanographene predicted in the 1970s, which conclusively demonstrates that carbon in very specific forms has magnetic properties that could permit future spintronic applications. The results have just been published in the renowned journal Nature Nanotechnology.
Depending on the shape and orientation of their edges, graphene nanostructures (also known as nanographenes) can have very different properties – for example,...
03.12.2019 | Event News
15.11.2019 | Event News
15.11.2019 | Event News
13.12.2019 | Physics and Astronomy
13.12.2019 | Physics and Astronomy
13.12.2019 | Materials Sciences