Boosting Efficient Ammonia Synthesis over Atomically Dispersed Co-Based Catalyst via the Modulation of Geometric and Electronic Structures

• Main Authors: Jiang, L. (Author), Jiang, Y. (Author), Lin, J. (Author), Peng, X. (Author), Qi, H. (Author), Wang, C. (Author), Wang, X. (Author), Zhang, T. (Author), Zheng, L. (Author), Zhou, Y. (Author)
• Format: Article
• Language: English
• Published: Chinese Chemical Society 2022
• Subjects: ammonia synthesis; coordination number; electron transfer; geometric structure; intermediate species
• Online Access: View Fulltext in Publisher
• ISBN: 20965745 (ISSN)
• DOI: 10.31635/ccschem.021.202100912

Ammonia (NH3) synthesis at mild conditions is of great significance, while the significant bottleneck of this process is the activation of N2 to realize the desired NH3synthesis performance, which requires deep insight and rational design of active sites at the atomic level. Here, were synthesized atomically dispersed Co-based catalysts with different Co-N coordination numbers (CNs) to explore the coordination-sensitive NH3synthesis reaction for the first time. Our studies showed that Co-based catalysts increased the NH3synthesis rate gradually with a decrease in CN. The Co-N2 catalyst exhibited the highest NH3synthesis rate of 85.3 mmol gCo -1 h-1 at 300°C and 1 MPa, which outperformed most of the previously reported Co-based catalysts. Various characterizations and theoretical calculations demonstrated that atomically dispersed Co catalyst with low CN could generate more unoccupied Co 3d charges and tetrahedral cobalt(II) sites. The unoccupied Co 3d charge, in turn, promoted the electron donation from the Co active center to the antibonding π-orbital (π*) of N2 and expedites N2 hydrogenation. Furthermore, the Co-N2 catalyst with more tetrahedral cobalt(II) sites could effectively facilitate the desorption of N-containing intermediate species (such as*NH3and*N2H4) to obtain a high NH3synthesis rate. © 2022 CCS Chemistry.All right reserved.