A study of corrosion stability of 50PtCoCr/C cathode catalyst

Abstract

The corrosion stability (under the chemical effect of acid environment and cycling of electrode potential) of 50 wt % PtCoCr/C trimetallic cathode catalyst has been studied. It is proposed that the dominant mode of degradation is dissolution of platinum nanoparticles and their redeposition on a surface. The values of activation energy of electrolytic reduction of molecular oxygen on 50 wt % PtCoCr/C catalysts, as well as the activation energy of its corrosion in 0.5 M H2SO4 solution, have been determined. The high corrosion stability of PtCoCr/C catalyst is attributed to the lower extent of filling of platinum surface with oxygen-containing particles (Q O/2Q H), which constitute the initial stage of platinum dissolution. It has been shown that the decrease in mass activity in electrolytic reduction of O2 during cycling of potential at 20°C up to 4000 cycles is 15%, which is significantly higher than for the monoplatinum system. The above-proposed mechanism of catalyst degradation in model experiments can lead to permanent loss of Pt ions in electrolyte bulk. In the case of measurements in a fuel cell (FC), a degradation mechanism described as dissolution of platinum nanoparticles and their redeposition on surface can be accompanied (as a consequence of a low amount of electrolyte in the FC) with redeposition of platinum particles in polymeric electrolyte.