The oxidation of CO on nanoporous Au (NPG), in particular the activation of molecular O(2), was investigated by a combination of kinetic and temporal analysis of products (TAP) measurements. Continuous reaction measurements in a flow of reaction gas, at atmospheric pressure, show a catalytic behavior of the NPG, with the activity decreasing to 33% of the initial activity over 1000 min on stream. In contrast, during simultaneous pulsing of CO and O(2), the formation of CO(2) on the NPG catalyst rapidly decreased to values below the detection limit after reactive removal of the surface oxygen species present after sample preparation. Possible mechanisms explaining this discrepancy are discussed, using further information from multi-pulse TAP experiments, which revealed that molecular O(2) can be activated and stored on NPG catalyst at room temperature, though with a low probability. (C) 2010 Elsevier Inc. All rights reserved.