Highly active vanadium-based nitrogen carrier doped with transition metals during chemical looping ammonia synthesis

The current challenge in the advancement of chemical looping ammonia synthesis (CLAS) technology lies in the poor reaction efficiency of binary transition metal nitrogen carriers (NC), which are limited to a single type. A new type of VN NC modified through the doping with transition metals (Ni, Fe, Co) has been investigated. The loading of Ni, Co and Fe significantly enhances the capability of VN to catalyze the dissociation of H 2 and increased the quantity of surface nitrogen vacancies (Nv), thereby promoting the transformation of nitrogen lattice to produce NH 3 . Theoretical calculation indicated that the presence of Ni is also indicative of its role in promoting the decomposition of H 2 and improving the affinity of lattice nitrogen for H*. The addition of 25 wt% Ni as a dopant has a pronounced activation effect on the VN. This results in a substantial increase in the lattice nitrogen conversion rate from 3.3% to 49.2%. The rate of ammonia production escalated from 30.5 μmol g −1 ·h −1 to 508 μmol g −1 ·h −1 . The Ni-VN demonstrates a sustained selectivity of 87% towards NH 3 at 850 °C. After conducting 8 cycles of experiments, it was observed that the activity of Ni-VN did not exhibit a significant decrease. This study offers a novel viewpoint on the advancement and formulation of transition metal-based NC, which contributes to the progress of low-carbon, environmentally friendly synthetic ammonia technology.