Anchoring Bond between Ru and N Atoms of Ru/Ca2NH Catalyst: Crucial for the High Ammonia Synthesis Activity

Key functions for the stability and activity of Ru catalysts for ammonia synthesis were examined by X-ray absorption fine structure (XAFS) experiments. Ru K-edge XAFS measurements were carried out for two Ru catalysts, Ru/Ca2NH and Ru/CaNH, which include N atoms in the supports. The stable Ru N bond was observed in the Ru/Ca2NH catalyst, but not in the Ru/CaNH catalyst, which was also supported by theoretical calculations in terms of Ru anion bond strength. The bond observed in the Ru/Ca,NH works to anchor the Ru nanoparticles to the Ca2NH support, and the activity has been maintained. Formation of anchoring bonds between catalyst particles and supports is essential to create highly active and long lasting catalysts.