【Haichuan Chemical Salary News Sharing】Qingdao University scholars achieve electrocatalytic nitrogen fixation to produce ammonia and nitrates at room temperature
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Nitrogen is the most abundant element in air and one of the basic elements that make up amino acids; it plays a crucial role in living organisms. How to achieve efficient nitrogen fixation has long been regarded as one of the \"holy grails\" of chemistry. Recently, Ding Xin, Zhang Lixue, and their colleagues from Qingdao University made significant progress in the field of electrocatalytic nitrogen fixation, reporting a bifunctional catalyst that enables the electrocatalytic reduction of nitrogen to ammonia and the oxidation of nitrogen to nitrates at room temperature.
Nitrogen in living organisms originates from biological nitrogen fixation enzymes and ammonium and nitrate produced by lightning. Industrially, ammonia (the main raw material for ammonium salts) primarily comes from the Haber–Bosch process developed 100 years ago, and ammonia is then used to synthesize HNO3 through the Ostwald process. However, the production conditions required for these two processes are extremely stringent; they consume large amounts of energy and generate significant amounts of greenhouse gases. It is therefore urgent to develop a more efficient and environmentally friendly nitrogen fixation process.
Electrocatalytic nitrogen fixation, which involves the electrochemical reduction of nitrogen to produce ammonia (NRR) using water and nitrogen, as well as the oxidation of nitrogen to produce nitric acid (NOR), allows for the conversion of electrical energy generated from renewable sources into ammonia or nitric acid – substances that are easy to store and transport. This approach ensures zero emissions of carbon dioxide, offering a new solution to the current severe energy and environmental problems. However, since this reaction involves the breaking of the N≡N bond in nitrogen (941 kJ mol-1), it is highly kinetically difficult to proceed. Furthermore, the presence of strong competitive reactions (water splitting reactions) severely limits the efficiency of electrocatalytic nitrogen fixation.
The team designed and synthesized a novel Fe-SnO2 catalyst, in which the iron element can be divided into oxygen-vacancy-anchored single-atom iron and lattice-doped iron, which are used respectively to enhance the adsorption and activation of nitrogen molecules on the catalyst surface and to improve the electrical conductivity of SnO2. Single-atom iron anchored by oxygen vacancies can **reduce the activation energy barrier for nitrogen molecules, thereby significantly enhancing the activity of NRR and NOR. In an acidic electrolyte, the NH3 yield of NRR reached 82.7 μg h-1 mgcat-1, with a Faradaic efficiency of 20.4%. Furthermore, in acidic electrolytes, this catalyst also exhibited excellent NOR catalytic activity (NO3- yield of 42.9 μg h-1 mgcat-1, Faradaic efficiency of 0.84%). This study provides new approaches for the design of efficient and stable electrocatalytic nitrogen fixation catalysts. This achievement was recently published in Angew. Chem. Int. Ed., with Zhang Linlin, a young teacher at Qingdao University, as the first author of the paper.
Research is good, but it’s unknown how long before it will be practical. New energy has been around for almost a hundred years, yet electric vehicles still can’t compete with those powered by gasoline