Density functional theory (DFT) cluster studies on the MoO3 (0 1 0) surface are carried out to examine formation of different locations of terminal oxygen vacancies and adsorption of NO in this work. The formation of two adjacent terminal oxygen vacancies requires almost twice energy of formation of one terminal oxygen vacancy, and the formation of two adjacent terminal oxygen vacancies is slightly easier than that of two diagonal terminal oxygen vacancies. NO can only adsorb on the cluster holding terminal oxygen vacancy and preferentially occupies the terminal oxygen vacancy site with N bonds to the surface. The increase of N-O bond length and the decrease of N-O bond order before and after NO adsorption indicate that one terminal oxygen vacancy can improve the activation of NO. The presence of another surrounding terminal oxygen vacancy further promotes the adsorption ability and the activation of NO. (C) 2011 Elsevier B.V. All rights reserved.