Carbon-supported Pd–Co as cathode catalyst for APEMFCs and validation by DFT

Abstract

Carbon supported PdCo catalysts in varying atomic ratios of Pd to Co, namely 1 : 1, 2 : 1 and 3 : 1, were prepared. The oxygen reduction reaction (ORR) was studied on commercial carbon-supported Pd and carbon-supported PdCo nanocatalysts in aqueous 0.1 M KOH solution with and without methanol. The structure, dispersion, electrochemical characterization and surface area of PdCo/C were determined by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and Cyclic Voltammetry (CV), respectively. The electrochemical activity for ORR was evaluated from Linear Sweep Voltammograms (LSV) obtained using a rotating ring disk electrode. The catalysts were evaluated for their electrocatalytic activity towards oxygen reduction reaction (ORR) in Alkaline Polymer Electrolyte Membrane Fuel Cells (APEMFCs). PdCo(3 : 1)/C gives higher performance (85 mW cm(-2)) than PdCo(1 : 1)/C, PdCo(2 : 1)/C and Pd/C. The maximum electrocatalytic activity for ORR in the presence of methanol was observed for PdCo(3 : 1)/C. First principles calculations within the framework of density functional theory were performed to understand the origin of its catalytic activity based on the energy of adsorption of an O(2) molecule on the cluster, structural variation and charge transfer mechanism.

Gold-promoted structurally ordered intermetallic palladium cobalt nanoparticles for the oxygen reduction reaction

“…So the core-shell structure of the particles remains intact up to 600°C whereas at 700°C the coreshell structure is undone forming random alloys and further increase in temperature leads to restructuring of ordered intermetallic alloys. Moreover on the basis of the PdCo binary alloy phase diagrams, Pd and Co forms random alloys at elevated temperatures, which lowers their activity and stability for ORR 29,[46][47][48] . The ORR activity is also affected by the pH and leads to different mechanism in acid and alkaline media 49 .…”

Dendritic defect-rich palladium–copper–cobalt nanoalloys as robust multifunctional non-platinum electrocatalysts for fuel cells

“…Platinum (Pt) is widely applied as a catalyst for anode and cathode reactions in FCs 4 – 8 , but many factors, including high cost that accounts for over 55% of the total cost 9 , scarcity, poor durability, and sluggish reaction kinetics of the oxygen reduction reaction (ORR), tremendously impede the commercial application of FCs. Therefore, developing highly effective non-Pt alloy catalysts for FCs has aroused great interest and concern of researchers from all over the world since such alloys can enhance the catalytic performance through optimizing the binding energy between reactants, intermediates and products with the alloy surface at the nanoscale 10 – 13 . For instance, Linic’s group, Yoo’s group, and Yang’s group, respectively reported Ag–Co alloy, Rh–Sn alloy, Pd–Rh alloy, and Au–Rh alloy catalysts for electrochemical ORR in basic media 14 – 18 .…”

“…As we know, the size, composition and complex shape (e.g., a dendritic shape) can be used to tune the electrocatalytic performance of Pd-based catalysts. Furthermore, many parameters, such as Pd–Pd interatomic distance, the number of Pd nearest neighbors, the d -band center of Pd and the Pd content on the nanoalloy surface, will change when Pd alloys with 3 d transition metals 10 , 12 , 13 . Therefore, rational regulation of these parameters can boost the catalytic activity and/or durability of Pd-based nanocatalysts for ORR and/or small organic molecular oxidation.…”

Preparation and Characterization of Nano Structured Pt−MOx/C for Oxygen Reduction Reaction in Acidic Medium

“…This can be due to the low concentration of ZrO 2 or partial ZrO 2 entering into Pt crystalline lattice [45][46][47][48]. For Pt-TiO 2 /C electrocatalyst we can notice that; Pt(111) Pt (200) and Pt(220) diffraction planes are found to be at higher 2θ values when compared to those in Pt/C -1 as in Table 1 resulting in a crystal lattice contraction, it is also noticed from Fig.1 (a) that; no characteristic peak for TiO 2 is found in XRD pattern, this could be interpreted by the existence of the titanium oxide in an amorphous form [49]. Pt (200) diffraction planes of Pt-CeO 2 /C-1, showed 2θ shift to higher values 47.326 when compared to that of Pt-CeO 2 /C47.319 as seen from Fig.1b CeO 2 /C-1 leads to crystal lattice contraction.…”