Evaluating the role of carbon radicals on Photocatalytic Nitrogen Fixation on Titania
EMSL Project ID
50511
Abstract
Photocatalytic fixation of nitrogen by titania catalysts at ambient conditions has been reported for decades, yet the active site capable of adsorbing an inert N2 molecule at ambient pressure and the mechanism of dissociating the strong dinitrogen triple bond at room temperature remain unknown. Prior work by the team has probe this reaction using in situ near-ambient-pressure XPS and density functional theory to probe the active state of the rutile (110) surface. The experimental results indicate that photon-driven interaction of N$_2$ and TiO2 is only observed if adventitious surface carbon is present, and computational results show a remarkably strong interaction between N2 and carbon substitution sites that act as surface-bound carbon radicals. A carbon-assisted nitrogen reduction mechanism is proposed and shown to be thermodynamically feasible. The findings provide a molecular-scale explanation for the long-standing mystery of photocatlaytic nitrogen fixation on titania. The results also suggest that control of carbon-based active sites is critical for reproducibility in photocatalysis and may provide an efficient strategy for engineering more efficient photo(electro)catalysts for nitrogen fixation. Therefore, the guiding hypothesis for the work to be further investigated at PNNL is that carbon radicals driven nitrogen photofixation. We propose to study this using Electron paramagnetic resonance spectroscopy (EPR) and Temperature programmed desorption (TPD) experiment at PNNL.
Project Details
Project type
Exploratory Research
Start Date
2018-10-21
End Date
2019-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members