Water impurities in the gas stream have a strong inhibiting effect. In the concentration range of 1-100 ppb,
the presence of water vapor influences the surface composition and the apparent rate coefficient
This is especially relevant in the temperature range of 600-700 K where most experimental kinetic studies are performed
Apparent activation barriers determined over this temperature range vary from 28.4 (1 ppb H2O) to 54.8 kcal/mol (100 ppb H2O).