Fig. 2: Revealing the critical potential for metal-oxide phase transition being at the centre of PEMFC cathode potential range.
From: Metal-oxide phase transition of platinum nanocatalyst below fuel cell open-circuit voltage
a Metal Pt fcc lattice constant variations and (b) surface-fraction-normalised scattering intensity variations of the Pt fcc phase and intensity of the first non-fcc Pt-Pt distance (3.3 Å) during cyclic voltammetry experiment in PEMFC between 0.05 and 1.23 V vs. RHE at 20 mV s−1. c Surface-fraction-normalised scattering intensity variations of Pt fcc phase during cyclic voltammetry experiment in PEMFC (red markers) and in electrochemical flow cell fed with 0.1 M HClO4 (green markers) between 0.60 and 1.0 V vs. RHE at 5 mV s−1. d Evolutions of the surface-fraction-normalised scattering intensity variations of the Pt fcc phase (orange) and intensity of the first 3.3 Å non-fcc Pt-Pt distance (blue) as a function of the fuel cell current density measured in a separated dedicated experiment (see Methods for fuel cell testing conditions). The orange boxes in (a, c) represent the PEMFC practical voltage range between 0.60 and 1.0 V vs. RHE, corresponding to the voltage of maximum power density and the open circuit voltage, respectively. In (b, c), the scattered intensity variations of the Pt fcc phase are normalised by their values at E = 0.4 V vs. RHE and E = 0.60 V vs. RHE, respectively. Errors bars correspond to the standard deviations associated with the refinements or computation of the different parameters. The X-ray transparent PEM cell was operated at 80 °C with H2/N2 at anode/cathode, 104/400 sccm flow rates, 52 % relative humidity and 100 mbar backpressure. The conventional cell was operated at 80 °C with H2/O2 at anode/cathode, 314/496 sccm flow rates, 100 % relative humidity and 500 mbar backpressure. The cathode potential is corrected from the cell's high-frequency resistance. Source data are provided as a Source Data file.
