Spontaneous oscillations during CO oxidation by 02 over Rh/Al2O3 catalysts have been investigated for stoichiometric (2C0:10(2)) and net oxidizing (1CO:60(2)) cases using parallel application of time-resolved Rh K edge energy dispersive X-ray absorption spectroscopy (XAFS), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and online mass spectrometry (MS). Whilst oscillatory chemistry is clearly visible over a range of temperatures and feedstock compositions, no evidence can be found for the participation of any IR active surface carbonyls to this chemistry. Equally, Rh K edge XAFS yields no evidence for reduction/oxidation cycles in the supported Rh as underlying the oscillatory behavior at the gas inlet (surface) of the sample bed or at varying axial positions below this point. In the stoichiometric case, variations in sample temperature are observed by both in DRIFTS and in a thermocouple inserted at the top of the catalyst bed. Oscillations occurring under net oxidizing conditions (378 K), however, yield no such detectable thermal variations during CO oxidation. These observations are discussed in terms of previously suggested mechanisms to explain this spontaneous behavior and in terms of the sensitivity of the applied probes to various aspects of the reactive system. (C) 2014 Elsevier Inc. All rights reserved.