We have comparatively studied adsorption and decomposition of NO on Au(9 9 7) and Au(1 1 0)-(1 x 2) surfaces by means of TDS, XPS, and OFT theoretical calculation. The lowest-coordinated Au atoms on both surfaces are 7-coordinated, but the surface chemistry of NO differs very much on these two surfaces. An alpha-NO species dominates on the Au(9 9 7) surface, while besides the similar alpha-NO species, another less stable and more abundant beta-NO species also appear on the Au(1 1 0)-(1 x 2) surface. Part of alpha-NO species decomposes into O adatom and N2O upon heating, but the less stable beta-NO species exhibits a much higher decomposition reactivity than alpha-NO species and facilely decomposes into O adatom and N2O on the Au(1 1 0)-(1 x 2) surface during the NO exposure at 105 K. The accompanying DFT theoretical calculation results demonstrate that chemisorbed (NO)(2) dimer species dominate the surface chemistry of NO on the Au surfaces. alpha-NO species is the most stable (NO)(2) dimer species that chemisorbs on the 7-coordinated ridge Au atoms of both Au(9 9 7) and Au(1 1 0)-(1 x 2) surfaces via the N atoms and exhibits a high activation barrier for the decomposition reaction. beta-No species corresponds to less stable (NO)(2) dimer species that chemisorbs on the trench Au atoms of the Au(1 1 0)-(1 x 2) surface via both N and O atoms and exhibits a low activation barrier for the decomposition reaction. These comprehensive experimental and theoretical calculation results reveal at the molecular level the origin of structure sensitivity and low-temperature catalytic activity of supported Au nanocatalysts in NO decomposition reaction. (C) 2013 Elsevier Inc. All rights reserved.