Figure 4: Electrochemical characterization Pd–W/OMCs.
(a) CV curves of commercial Pt/Vulcan (black line), W/OMCs (red line) and Pd–W/OMCs (blue line), showing that Pd doping positively shifts the reduction potential of oxygen at the W/OMCs modified electrode and increases the current intensity of ORR. Potentials are specified with reversible hydrogen electrode (RHE) as reference. (b) Polarization curves of ring (dotted line) and disc (solid line) electrodes at 1,600 r.p.m. by coating Pt/Vulcan (black), W/OMCs (red) and Pd–W/OMCs (blue) onto disc electrode, scan rate: 10 mV s−1. (c) Percentage of peroxide (solid line) and the electron transfer number (n; inset, dotted line) of Pt/Vulcan (black), W/OMCs (red) and Pd–W/OMCs at various potentials, based on the corresponding RRDE data in b. (d) Fuel cell performance plots for different cathode with the same metal loading at an accessed Pd/Vulcan coated anode (black circles: Pt/Vulcan, blue square: Pd–W/OMCs, red triangle: W/OMCs) using 3 M formic acid as fuel and electrolyte, non-humidified 5 bar oxygen as oxidant. (e) Corresponding I–V curves of the fuel cell in d. (f) Power output per milligram (precious metal) of the fuel cell over time using Pt/Vulcan (dashed line) and Pd–W/OMCs as cathode materials.
