Effect of Potassium Doping on the Surface Structure and Ammonia Synthesis Activity of Co/MgO

The development of effective catalysts for ammonia synthesis under mild conditions is crucial for the mitigation of global warming. Recently, supported Co catalysts have been of great interest, and it is important to investigate the doping effects of basic promoters, such as potassium (K), having strong electron-donating properties. Here we show that even a small amount of K doping (K/(K + Mg) = 0.5-1 mol %) to Co/MgO increases the ammonia synthesis rate of Co/MgO by twice. Moreover, our results revealed that the reduction conditions, such as the temperature and time, strongly affect the amount, chemical state, and arrangement of K species, thereby significantly impacting the NH₃ synthesis activity. The findings of this research will contribute to understanding of the effect of alkaline promoters on Co catalysts used for various reactions.