Recently, our groupwas invited to co-author a Primer article titled “Methods for the Reduction and Oxidation of Nitrogen” with a number of international colleagues, including Professor Yang Shao-Horn from MIT, Professor Ib Chorkendorff from the Technical University of Denmark, Professor Ifan EL Stephens from Imperial College London, and Professor Andrew J. Medford from Georgia Institute of Technology. The article discusses the research techniques and methods in the field of nitrogen reduction and oxidation.

Nitrogen is one of the elements necessary for all forms of life. However, nitrogen molecules are extremely inert, and their reduction to ammonia or oxidation to nitrogen oxides requires overcoming large kinetic resistance. At present, the activation and conversion of nitrogen mainly relies on the industrial ammonia synthesis process dominated by the Haber-Bosch process. This process necessitates harsh reaction conditions, high energy consumption, and large CO₂ emissions, so it is in urgent need of upgrading. In recent years, green N₂ activation and conversion methods driven by renewable energy, namely low-pressure and low-temperature thermal catalytic ammonia synthesis, (photo) electrocatalytic nitrogen reduction and nitrogen oxidation, have received widespread attention from academia and industry. These studies are currently very challenging, especially in the (photo) electrocatalytic ammonia synthesis reaction, the yield and selectivity of NH₃ are both low, which makes the quantitative analysis of the product more difficult, and the results reported in the literature often have certain accuracy and repeatability problems. Therefore, it is necessary to establish a set of rigorous experimental methods.

In this article, the author first reviewed the development history of N₂ activation and conversion, and analyzed its reduction/ oxidation process driven by heat/ electricity/ light in combination with theoretical calculations; then, according to different N₂ activation and conversion methods, a set of step-by-step experimental guidance schemes was proposed, which detailed the experimental equipment, product detection methods, possible sources of pollutants, catalyst performance evaluation, analysis of experimental results, theoretical calculation methods, etc. According to this guidance scheme, the results reported in the literature were compared and analyzed. The author focused on the errors that are prone to occur in this research field and the corresponding solutions, and gave methods to improve experimental repeatability and strategies to reduce experimental costs. The article proposes that the important research field of N₂ activation and conversion requires more stringent experimental methods and technical standards to avoid false positive experimental results, thereby ensuring the correctness of the research direction and laying the foundation for the establishment of new technologies in the future.

This introductory article, titled "Methods for nitrogen activation by reduction and oxidation", was recently published in Nature Reviews Methods Primers, and a graphical summary of the introductory overview (PrimeView) was also distributed at the same time. Zhang Xilun, a 2014 doctoral student in DNL1901 of our institute, was responsible for writing the experimental technology and analytical methods for thermal catalytic synthesis of ammonia in the article, and summarized and analyzed the performance of the recently developed new catalysts. This work was funded by the National Natural Science Foundation of China's Science Center Project. (Text/Photo by Zhang Xilun)

Article link: https://doi.org/10.1038/s43586-021-00053-y