Au-Ni bimetallic clusters were identified as possible automobile catalysts that do not contain a platinum group metal (PGM). The Au-Ni bimetallic clusters were prepared as nanoparticles of Au and Ni using a polyol method. The oxidation states of the Au and Ni species and catalytic activities were studied simultaneously under a NO-CO stream using time-resolved operando X-ray absorption fine structure (XAFS) analysis. Under the investigated reaction conditions, the clusters pretreated by O-2 initially composed of mixtures of Au and NiO were easily reduced to bimetallic Au-Ni nano-particles. The Au atoms promote the release of oxygen from nearby NiO within the cluster. The resulting Au-Ni alloy species exhibit NO purification activity matching that of Rh. (C) 2016 Elsevier B.V. All rights reserved.