N(2)O direct decomposition over Fe-beta zeolite prepared by wet ion-exchange (WIE) was systematically investigated based on the experimental and theoretical studies in this paper. Both isolated iron ions in the charge compensation positions and highly dispersed FeO(x)-like crystallite were verified by means of H(2)-TPR. Catalytic performances of various Fe-BEA zeolites with diverse iron contents were thereafter studied. The results showed that: (1) the catalytic activity of bare beta zeolite was significantly promoted via ion-exchange; (2) no obvious further increase in deN(2)O activity was observed for Fe-beta samples with iron contents higher than 1%. Two kinds of reaction mechanism, with respective formation of oxygen (O(2)) or nitrogen oxide (NO(x)) intermediate, for the direct decomposition of N(2)O over Fe-beta zeolite (noted as Fe-Z) were proposed according to the N(2)O-TPD, NO(2)-TPD, N(2)-TPD, N(2)O-TPSR, and in situ DRIFTS investigation and density functional theory (DFT) study. The corresponding energy calculations for O(2)-formation mechanism revealed that O(2) desorption was the rate determining step with an energy barrier of 63.20 kcal/mol. Another mechanism with NO formation was also simulated by DFT calculations, whose energy calculations indicated that the formation of Fe-Z-(NO)(2) was the main pathway for NO generation with an energy barrier of 26.92 kcal/mol. (C) 2011 Elsevier B.V. All rights reserved.