The oxygen reduction reaction on carbon-supported platinum electrocatalysts (Pt/C) has been investigated as a function of temperature by employing the technique of cyclic thermammetry. A novel electrochemical cell has been designed which allows the concomitant measurement of the potentio-static current from the oxygen reduction reaction (ORR) and accurate control of the aqueous electrolyte temperature, allowing cyclic linear temperature sweeps between 25 and 80 degrees C at speeds up to 40 mK s(-1). Our method provides new insight into the temperature dependent degradation of the cathodic oxygen reduction reaction in aqueous sulfuric acid systems. Cycling the temperature accelerates the degradation of the cathodic current through loss of active surface area. Two simultaneously operating mechanisms are proposed to account for this loss. One mechanism is described by physical detachment of the platinum and carbon particles under thermal fatigue, and the other by anodic dissolution of the Pt electrocatalyst. The forms of these are discussed. (C) 2011 Elsevier B.V. All rights reserved.