Abstract:
We have investigated the formation of ammonia (NH
3) from atomic N and water (H
2O) on a rutile(R)-TiO
2(110) surface using the temperature-programed desorption method. The formation of NH
3 can be detected after coadsorption of atomic N and H
2O on the R-TiO
2(110) surface, desorbing from the 5-fold coordinated Ti
4+ (Ti
5c) sites at about 400 K, demonstrating that the NH
3 formation on R-TiO
2(110) is feasible at low surface temperature. During the process, both hydroxyl groups at the bridging oxygen rows and H
2O on the Ti
5c sites contribute to the formation of NH
3, which are affected by H
2O coverage. At low H
2O coverage, the direct hopping of hydrogen atoms may be the dominant process for hydrogen transfer; while H
2O-assisted hydrogen atoms diffusion may be preferred at high H
2O coverage. Our result will be of significant help to get a deeper insight into the fundamental understandings of hydrogenation processes during the NH
3 synthesis.