Experimental and theoretical studies of ammonia generation: Reactions of H2 with neutral cobalt nitride clusters
Abstract
Ammonia generation through reaction of H2 with neutral cobalt nitride clusters in a fast flow reactor is investigated both experimentally and theoretically. Single photon ionization at 193 nm is used to detect neutral cluster distributions through time-of-flight mass spectrometry. ComNn clusters are generated through laser ablation of Co foil into N2/He expansion gas. Mass peaks ComNH2 (m = 6, 10) and ComNH3 (m = 7, 8, 9) are observed for reactions of H2 with the ComNn clusters. Observation of these products indicates that clusters ComN (m = 7, 8, 9) have high reactivity with H2 for ammonia generation. Density functional theory (DFT) calculations are performed to explore the potential energy surface for the reaction Co7N + 3/2H2 → Co7NH3, and a barrierless, thermodynamically favorable pathway is obtained. An odd number of hydrogen atoms in ComNH3 (m = 7, 8, 9) probably come from the hydrogen molecule dissociation on two active cobalt nitride clusters based on the DFT calculations. Both experimental observations and theoretical calculations suggest that hydrogen dissociation on two active cobalt nitride clusters is the key step to form NH3 in a gas phase reaction. A catalytic cycle for ammonia generation from N2 and H2 on a cobalt metal catalyst surface is proposed based on our experimental and theoretical investigations.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Sep 24, 2012
- Source ID
- 10.1063/1.4754158
Entities
People
- Elliot R. Bernstein
- Shi Yin
- Yan Xie
Organizations
- Air Force Office of Scientific Research
- Colorado State University
- National Science Foundation