Theoretical Study on Adsorption and Dissociation of NO2 Molecule on Fe(111) Surface

We applied periodic density-functional theory (DFT) to investigate the adsorption and dissociation of NO2 on a Fe(111) surface. The most favorable adsorption configuration of NO2/Fe(111) is the FeNO2(S-μ3-N,O,O′) configuration with NO2 at the 3-fold-shallow site of the surface, which has an adsorption energy −64.59 kcal/mol. Of two geometries of NO2/Fe(111) for the stepwise NO2 deoxygenation, one is the most stable structure, FeNO2(S-μ3-N,O,O′), with activation barriers 10.38 and 19.36 kcal/mol to break the first (ON−O bond activation) and second (N−O bond activation) nitrogen−oxygen bonds, respectively; another configuration FeNO2(B-μ2-N,O) has a smaller energy barrier (3.88 kcal/mol) to break the first ON−O bond. All these findings show that NO2 can readily decompose on the Fe(111) surface. The rate constants for the two aforementioned processes were also predicted by VTST and RRKM theory, and the predicted total rate constants, ktotal (in units of cm3 molecule−1 s−1), can be represented by the equations ktotal = 5.61 × 10−5T−2.060 exp(−0.639 kcal mol−1/RT) at T = 100−1000 K. To acquire insight into the great catalytic activity of the Fe(111) surface for the decomposition of NO2, the nature of the interaction between the adsorbate and the substrate is subjected to a detailed electronic analysis.