Kinetic investigation of oxygen reduction reaction in sub-freezing acid media

A three-electrode system with 2 M H2SO4 as the electrolyte was developed to investigate the oxygen reduction kinetics on Pt/C catalyst at sub-freezing temperatures. This system successfully avoided the ice formation above −10 °C. Furthermore, the influence of different membrane electrode assembly (MEA) status, i.e. the membrane hydration and the electrode structure, on the kinetic results in a sub-freezing fuel cell was diminished in this method. By cyclic voltammetry (CV) test, the electrochemical active surface area (ECA) of Pt/C catalyst at sub-freezing temperatures was obtained. Results showed that the ECA at sub-freezing temperatures was almost the same as that at room temperature, either the H-desorption or the H-adsorption process at subzero temperatures still took place in the same way. According to the analysis of the linear scan voltammetry (LSV), the kinetics of oxygen reduction on Pt/C catalyst at sub-freezing temperatures was explored. The limiting current density decreased as temperature dropped and the exchange current density at subzero temperatures still obeyed the Arrhenius theory.