Palladium/Cobalt Coated on Multi‐Walled Carbon Nanotubes as an Electro‐catalyst for Oxygen Reduction Reaction in Passive Direct Methanol Fuel Cells

This work reports the synthesis of Pd‐based alloy electrocatalysts of Co supported on multi‐walled carbon nanotubes (MWCNTs) and their evaluation as cathode materials in a passive direct methanol fuel cell (PDMFC). The X‐ray diffraction (XRD) analysis showed well‐defined reflections corresponding to a face centered cubic phase of palladium. As compared to the Pd/MWCNT electrocatalyst, the bimetallic alloy electrocatalysts with the different Pd_xCo atomic ratios showed highly enhanced mass activity (MA) for the oxygen reduction reaction (ORR); however, the significant enhancement in the specific activity (SA) by a factor of about 1.2–5.6 for the ORR was found on the Pd_xCo alloy electrocatalysts in the presence and absence of methanol electrolyte solution. This enhancement SA in of the Pd‐based electrocatalysts was correlated to the changes in the lattice parameter and Pd_xCo surface composition. Surface area changes of Pd‐based electrocatalysts supported on MWCNT were evaluated using an accelerated durability test (ADT). The results obtained using the ADT were correlated to the performance of the Pd‐based electrocatalysts in the PDMFC. A better performance was obtained for the cell using Pd₃Co/MWCNT (2.53 mW cm^–2) compared to Pd/MWCNT (1.64 mW cm^–2) and Pt/C‐Electrochem (1.20 mW cm^–2) as cathode in the PDMFC. In the presence and absence of methanol the impedance Bode spectra showed one time constant that associated to follow a four electron pathway.