The reaction of stable adsorbed, active surface oxygen (O-act) with H-2 on Au/TiO2 catalysts with the same Au loading, but varying Au particle size was studied by quantitative Temporal Analysis of Products reactor measurements between 80 degrees C and 400 degrees C and compared to the O-act removal by CO. The absolute amount of O-act for H-2 oxidation is identical to that in CO oxidation, and it also occurs at the Au-TiO2 interface perimeter, indicating that the O-act species for this reaction is identical to that for CO oxidation. Implications on the mechanism of the H-2 oxidation and the origin of the selectivity during the preferential CO oxidation (PROX) are discussed. (c) 2014 Elsevier Inc. All rights reserved.