Efficient bottom-up synthesis of new perovskite materials for ammonia production
Scientists have found a method to synthesize a special perovskite, which can promote the formation of ammonia, and ammonia has important applications in fertilizer production and hydrogen energy. This new synthesis process can be carried out at a much lower temperature and in a shorter time than the traditional method of synthesizing perovskite oxide materials, and the produced perovskite is superior to all competitors in the production of ammonia.
Perovskite is a kind of synthetic material, its crystal structure is similar to the natural mineral calcium titanate. They have always been the subject of many studies, because they show exciting and unique characteristics, which can be adjusted according to their composition. One of their potential applications is as a catalyst for ammonia synthesis. In other words, specific perovskite can be put in a reaction chamber with nitrogen and hydrogen to promote the reaction of these gases to produce ammonia.
Ammonia is a useful substance, which can be used to produce chemical fertilizers and man-made chemicals, and even as a carrier of clean energy (in the form of hydrogen), which may be the key to environmental protection technology. However, the synthesis itself with ammonia and perovskite has various challenges.
The rate of ammonia synthesis is usually limited by the high energy required to decompose nitrogen molecules. Some researchers have successfully utilized some precious metals, such as ruthenium. In recent years, perovskite, which replaces some oxygen atoms with hydrogen ions and nitrogen ions, has been developed as an efficient catalyst for ammonia synthesis. However, traditional perovskite substitution synthesis usually needs to be carried out at high temperature (over 800 ° C) and for a long time (several weeks).
In order to solve these problems, in a recent study conducted by Tokyo Tech, a group of researchers led by Professor Masaaki Kitano designed a new method to synthesize this oxygen substituted perovskite at low temperature, with the chemical name of BaCeO3? XNyHz, and tested its performance as a catalyst for ammonia production. In order to achieve this goal, they made innovative changes in the perovskite synthesis process. The use of barium carbonate and cerium dioxide as precursors (or “components”) requires very high temperatures to combine them into alkali perovskite or BaCeO3, because barium carbonate is very stable. In addition, oxygen atoms must be replaced by nitrogen and hydrogen ions. On the other hand, the team found that the compound barium carbonate amide could easily react with cerium dioxide under the flow of ammonia gas to directly form BaCeO3? XNyHz low temperature and shorter time. Professor Kitano explained: “This is the first demonstration of bottom-up synthesis of this material called perovskite type oxynitride.”
The researchers first analyzed the structure of perovskite obtained by the proposed process, and then tested its catalytic performance for low-temperature ammonia synthesis under different conditions. This proposed material not only outperforms most of the most advanced competitors when combined with ruthenium, but also greatly outperforms all competitors when combined with cheaper metals such as cobalt and iron. This has huge advantages in terms of performance and related costs.
Finally, the researchers tried to clarify the mechanism behind the improvement of ammonia synthesis rate. In conclusion, the insights provided in this study provide a solution for the synthesis of other types of nitrogen and hydrogen ion replacement materials and the intelligent design of catalysts. “Our research results will pave the way for a new catalyst design strategy for low-temperature ammonia synthesis,” concluded Professor Kitano. These findings are expected to make the synthesis of useful materials cleaner and more energy-saving.