Updates from the recent research shows researchers were able to overcome the bottleneck in ammonia synthesis through changes in the rate-determining step.
Industrial production of ammonia is mainly through the Haber-Bosch process, were nitrogen is fixed using the reducing agent hydrogen. Ammonia is essential for manufacturing of fertilizers and most nitrogen-containing organic chemicals. The process of production, however, requires harsh conditions and high temperatures and accounts for 1.5 percent of all energy consumption worldwide. This makes the process both necessary but requires an urgent need for sustainable and less energy-intensive solutions to produce ammonia.
An alternative to the traditional process known as the electrocatalytic N2 reduction reaction, uses water as the hydrogen source and is powered by renewable electricity. This process however, had substantial energy loss during the process and the activation of the inert nitrogen-nitrogen triple bond at the rate-determining step remained a challenge.
By this standard, the scientist from the Soochow University in Suzhou, China set out to discover a highly active catalysts that could alter the rate-determining step of electrochemical ammonia synthesis is expected to be an ideal candidate for ammonia synthesis.
Recent research published in the Beijing-based National Science Review; the team demonstrated their success in altering the rate-determining step of ambient ammonia synthesis by deliberate introduction of cobalt single clusters as electron-donating promoter in nitrogen-doped carbon. This process was able to achieve outstanding yield rate of ammonia. This new strategy would greatly reduce the energy loss of the system and cut down the fundamental cost, thus contributing to future practical applications.
Prof. Tao Qian said, "When chemically adsorbed on the cobalt cluster, N2 is spontaneously activated and experiences a significant weakening of the nitrogen-nitrogen triple bond due to the strong electron backdonation from the metal to the N2 antibonding orbitals, and the N2 dissociation becomes an exothermic process over the cobalt single cluster."
"Thus, the rate-determining step has been successfully shifted from the usual N2 activation to the subsequent hydrogenation with only a small energy barrier of 0.85 eV."
The team’s research has paved the way for potential future development of electrocatalysts for sustainable N2 reduction reaction systems.