[Photolysis of Gaseous HNO3 on the α-Fe2O3 Films Under 308 nm UV Light].

Under 308 nm UV light, photolysis of HNO3 in the gas phase and on the α-Fe2O3 films was studied by using ultraviolet-visible spectrophotometer (UV-Vis), Fourier transform infrared spectrometer (FTIR) combined with ion chromatography (IC) technique. The effects of HNO3 initial concentration, relative humidity (RH) and illumination time were systematically investigated. Results showed photolysis of HNO3 could produce NO2 and NO in the gas phase and on the α-Fe2O3 films. With the increase of reaction time and HNO3 initial concentration, the concentration of NO2 and NO were all increased exponentially. NO2 and NO concentrations produced from photolysis of HNO3 on α-Fe2O3 films were about 3.27 and 3.87 times higher than those in gas phase, respectively. And NO2 concentration was about 2 times higher than that of NO whatever photolysis of HNO3 in gas phase or on α-Fe2O3 films. HONO concentration increased in exponent regularity along with the increase of RH. The yield of HONO increased from 0.023 to 0.087 when RH from 20% increased to 90%. Surfaces effect played a leading role in photochemical reaction of gaseous HNO3 on the α-Fe2O3 films.