Reactions of NH2 Species with Hydrogen and NO on the Pt(100)-(1×1) Surface
The Journal of Physical Chemistry B
, E-ISSN: 1520-5207
Boreskov Institute of Catalysis, Prosp. Akademika Lavrentieva 5, Novosibirsk 630090, Russian Federation
The formation of the NH2,ads amino species and its further reactions with hydrogen and NO on the unreconstructed Pt(100) surface were studied by means of high-resolution electron energy loss spectroscopy (HREELS) and temperature-programmed reaction (TPR) spectroscopy. The NH2,ads amino species forms during the reaction between Hads and NO at 300 K. NH2,ads can be oxidized by NO at a temperature higher than 260 K. The reaction at T ≥ 300 K results in the evolution of N2 and water. An essential amount of Nads accumulates on the surface after the reaction at ∼260 K and desorbs as a low-temperature TPR peak of N2 at 320 K. TPR in a saturated coadsorption layer of NOads and NH2,ads prepared at 100 K shows an “explosive” behavior, manifesting itself in the evolution of narrow TPR peaks of N2 and H2O at ∼370 K. TPR in an unsaturated coadsorption layer of NOads and NH2,ads proceeds at a much lower temperature of <300 K, resulting in the “nonexplosive” desorption peaks of N2 and H2O. The reaction between the NH2,ads and Hads species in the temperature range of 350−470 K results in ammonia evolution. At T < 400 K, NH3 forms through the addition of a hydrogen atom to NH2,ads and competes with the Hads recombination. At higher temperature, >400 K, the dissociation of NH2,ads serves as a source of hydrogen atoms for the NH2,ads hydrogenation, leading to the parallel evolution of ammonia along with N2 and H2. The mechanism of the formation of NH2,ads species and its further reactions with NO and hydrogen on the Pt(100)-(1×1) surface are discussed in detail.