Mechanisms and kinetics of surface reactions in nanoporous platinum films were investigated. Nanoporous films of platinum of similar to 250 nm thickness were deposited on glass slides by co-sputtering Pt and carbon followed by subsequently burning off carbon in air at 450 degrees C. Electrical resistance was measured in air and in 10% H-2 + nitrogen at 80 degrees C as a function of time. The change in electrical resistance was extremely fast when switched to the H-2 + N-2 atmosphere. When switched to air, the film resistance increased with time at a much slower rate. The increase in resistance in air was attributed to the formation of Pt-oxide on the internal surfaces of the nanoporous films. The kinetics of oxidation was described by a model which includes two surface kinetic steps and a diffusional step. The use of nanoporous films makes it possible to investigate mechanisms and kinetics of surface reactions by ensuring a large surface to volume ratio. Oxide scale thickness at 80 degrees C in air after several hours of oxidation was only sub-monolayer. Oxide scale thickness after 3 h at 450 degrees C was about 1 nm. Implications of the results for proton exchange membrane fuel cell (PEMFC) Pt catalyst degradation are discussed. (C) 2014 Elsevier B.V. All rights reserved.