The extensive use of fossil fuels in industrial and transportation have arisen some issues for the environment such as air pollution, rises in sea level and frequency of extreme weather events. In order to lessen those negative effects of using fossil fuels, a sustainable source of renewable energy is needed to achieve the zero-carbon emission target. Toward this goal, the development of energy transportation based on the interconversion of the chemical compounds known as ‘energy carriers’ is highly important. Among the candidates for energy carriers, ammonia is promising because of several attractive features it possesses including zero carbon content, high energy density, low flammability and readily transported as a liquid. Ammonia is also produced globally on a huge scale (>150 million tons annually) by the Haber-Bosch process. While reduction of dinitrogen to ammonia by molecular complexes has been extensively studied, the reverse reaction, ammonia oxidation to dinitrogen using molecular complexes remains far less explored. However, this situation is rapidly changing, as four molecular catalyst systems were reported in 2019 for oxidation of ammonia to dinitrogen. Although recent scientific progress on oxidation of ammonia by molecular complexes has provided new insights into reactivity and catalyst design, there are several fundamental scientific challenges that present in the quest of designing efficient catalyst, including how to cleave three N−H bonds, form a bond between two nitrogens, and release of dinitrogen to complete the catalytic cycle. Therefore, this talk evaluates the challenges of designing molecular catalyst for oxidation of ammonia and highlight recent key contributions in this burgeoning area of research.
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