Dynamic nitroxyl formation in the ammonia oxidation on platinum via Eley–Rideal reactions

Abstract

For over 90 years, nitroxyl (HNO) has been postulated to be an important reaction intermediate in the catalytic oxidation of ammonia to NO and its by-products (N, NO), but never proven to form or exist on catalytic surfaces. Here we show evidence from reactive ion beam experiments that HNO can form directly on the surface of polycrystalline Pt exposed to NHvia Eley-Rideal abstraction reactions of adsorbed NH by energetic O and O projectiles. The dynamic formation of HNO in a single collision followed up by prompt rebound from the surface prevents subsequent reactive interactions with other surface adsorbates and enables its detection. In addition to HNO, NO and OH are also detected as direct products in what constitutes the concurrent abstraction of three surface adsorbates, namely NH, N, and H, by O projectiles with entirely predictable kinematics. While its relation to thermal catalysis may be tenuous, dynamic HNO formation could be important on grain surfaces of interstellar or cometary matter under astrophysical conditions.

In situprobing of Pt/TiO2activity in low-temperature ammonia oxidation

“…[1][2][3][4] Supported platinum systems are utilized in diesel vehicles, among others, as a part of ammonia slip catalysts responsible for NH3 oxidation to molecular nitrogen. 5,6 Both model platinum systems -single-crystals, foils, and gauzes, [7][8][9][10][11][12] as well as supported platinum catalysts, [13][14][15][16][17][18][19][20] have been studied in detail as catalysts for the ammonia oxidation reaction, mostly within the Ostwald process for nitric acid production. DFT calculations [21][22][23][24][25] and kinetic modeling [26][27][28] were performed to gain more insight into the mechanism.…”

Intramolecular water-splitting reaction in single collisions of water ions with surfaces

“…15,16 The ions were produced in an inductively-coupled plasma reactor, with tunable plasma potential. Ions were extracted, collimated, and launched into the ion beam line, held typically at –15 kV, then underwent magnetic mass filtering.…”

Unraveling the Lattice O Assisted Internal Selective Catalytic Reduction Mechanism on High N2 Selectivity of CuOx/PtCu Catalysts in NH3-SCO

“…Various methods to regulate the NH 3 -SCO selectivity have been applied to promote the N 2 production ratio on Pt-based catalysts. ,,− For instance, some research considers the modification of the acidity of the substrate to regulate NH 3 adsorption strength. Murayama et al demonstrate that reaction selectivity can be improved by controlling the acid sites of Pt/Nb 2 O 5 , , where the NH 4 + absorbed on Brønsted acid sites helped promote ammonia dehydrogenation via the hydrazine mechanism .…”