Low temperature ammonia synthesis from atomic N and water on rutile TiO2(110)

Abstract

We have investigated the formation of ammonia (NH3) from atomic N and water (H2O) on a rutile(R)-TiO2(110) surface using the temperature-programed desorption method. The formation of NH3 can be detected after coadsorption of atomic N and H2O on the R-TiO2(110) surface, desorbing from the 5-fold coordinated Ti4+ (Ti5c) sites at about 400 K, demonstrating that the NH3 formation on R-TiO2(110) is feasible at low surface temperature. During the process, both hydroxyl groups at the bridging oxygen rows and H2O on the Ti5c sites contribute to the formation of NH3, which are affected by H2O coverage. At low H2O coverage, the direct hopping of hydrogen atoms may be the dominant process for hydrogen transfer; while H2O-assisted hydrogen atoms diffusion may be preferred at high H2O coverage. Our result will be of significant help to get a deeper insight into the fundamental understandings of hydrogenation processes during the NH3 synthesis.