Dinitrogen fixation by alkali and alkaline earth hydride composites under plasma

The development of alternative methods for sustainable dinitrogen (N 2 ) fixation to ammonia (NH 3 ) is a cutting-edge research area. The presence of external stimuli, such as non-thermal plasma, can boost the activation of the inert N 2 molecules under ambient temperatures and pressures, thereby generating value-added products such as NH 3 or other nitrogen-containing compounds. Binary alkali metal hydrides such as NaH and KH have recently shown intriguing properties in the plasma nitrogen fixation process. Herein we report the different chemical behaviors of a series of hydride composites consist of potassium hydride (KH) and alkaline earth metal hydride (MgH 2 , CaH 2 , SrH 2 , and BaH 2 ) under nitrogen plasma conditions. A nitrogen-relayed mechanism has been proposed to understand the different nitrogen fixation behaviors on these hydride composites. Under this scenario, KH is responsible for plasma N 2 fixation to form surface NH 2 species, which subsequently migrate and react with MgH 2 , CaH 2 , and SrH 2 to form N and NH species, respectively. This work enriches the plasma chemistry of metal hydrides , and provides a strategy to enhance the amounts of fixed nitrogen of single hydride material under nitrogen plasma conditions. • Alkali and alkaline earth metal hydride composites exhibit different behaviors under nitrogen plasma. • A nitrogen relayed mechanism has been proposed for the KH/AeH 2 composite. • The fixed nitrogen on KH undergoes different fates depending on the alkaline earth metal hydride it is combined with.