The Stability Challenge on the Pathway to Low and Ultra-Low Platinum Loading for Oxygen Reduction in Fuel Cells

Abstract

We report the influence of catalyst loading on rates of platinum degradation in acidic electrolyte at room temperature. A piezoelectric printer is used to deposit spotted arrays of a commercially available catalyst comprised of Pt nanoparticles on a porous carbon support. The kinetically controlled oxygen reduction reaction (ORR) activity at different loadings is measured using an electrochemical scanning flow cell (SFC), and found to be quite stable over the range of loadings studied. This behaviour, however, contrasts sharply with rates of both transient and quasi-steady-state platinum dissolution. These are shown using downstream inductively coupled plasma mass spectrometry (ICP-MS) analytics, to increase as loading becomes lower. This dichotomy between activity and stability has direct implications for the development of improved catalyst materials, as well as for the achievement of current targets for reduced loadings of noble metals for fuel cells and other energy storage devices.