NO + H2 reaction on Pt(100). Steady state and oscillatory kinetics

Article abstract of DOI:10.1016/0039-6028(92)90174-5

The reaction of NO + H₂ on Pt(100) was studied in the 10^-6 mbar range between 300 and 800 K with mass spectrometry, work-function measurements, and video LEED. Both multiple steady states and kinetic oscillations were found. The principal reaction products were N₂, H₂O and NH₃, and the activity and selectivity of the reaction were seen to depend on the partial pressure ratio p_H(2)/p_NO, on the surface temperature, and on the degree of surface reconstruction. Whereas the 1 × 1 surface of Pt was active for both N₂ and NH₃ formation, a well-annealed hex phase exhibited a low catalytic activity. The occurrence of defects during the 1 × 1 hex transition was shown to lead to enhanced N₂ formation. At low p_H(2)/p_NO ratios, N₂ formation was favored, while for large p_H(2)/p_NO ratios NH₃ production was enhanced. Kinetic oscillations, as determined from variations in the N₂, H₂O and work-function signals, were found between 430 and 445 K.