Effect of the TiO2 phase and loading on oxygen reduction reaction activity of PtCo/C catalysts in proton exchange membrane fuel cells

Abstract

We investigated the effect of the TiO2 phase, as either pure rutile (TiO2(R)) or a 4 : 1 (w/w) anatase: rutile ratio (TiO2(AR)), and the loading on the activity of PtCo/C catalyst in the oxygen reduction reaction (ORR) in a proton exchange membrane (PEM) fuel cell. The incorporation of the different phases and loading of TiO2 on the PtCo/C catalyst did not affect the alloy properties or the crystalline size of the PtCo/C catalyst, but affected importantly the electrochemical surface area (ESA), conductivity of catalyst layer and the water management ability. The presence of TiO2(AR) at appropriate quantity can decrease the mass transport limitation as well as the ohmic resistance of catalyst layer. As a result, the optimum loading of TiO2(AR) used to incorporated in the layer of PtCo/C catalyst was 0.06mg/cm2. At this content, the TiO2(AR)-PtCo/C catalyst provided the highest current density of 438 mA/cm2 at 0.6V at atmospheric pressure in PEM fuel cell and provided the kinetic current in acid solution of 20.53 mA/cm2. In addition, the presence of TiO2(AR) did not alter the ORR electron pathway of PtCo/C catalyst. The electron pathway of ORR of TiO2(AR)-PtCo/C was still the four-electron pathway.