Surfactant-Free Synthesis of Reduced Graphene Oxide Supported Well-Defined Polyhedral Pd-Pt Nanocrystals for Oxygen Reduction Reaction

Oxygen Reduction Reaction Catalyzed by Pt3M (M = 3d Transition Metals) Supported on O-doped Graphene

Pt3M (M = 3d transition metals) supported on oxygen-doped graphene as an electrocatalyst for oxygen reduction was investigated using the periodic density functional theory-based computational method. The results show that oxygen prefers to adsorb on supported Pt3M in a bridging di-oxygen configuration. Upon reduction, the O–O bond breaks spontaneously and the oxygen adatom next to the metal–graphene interface is hydrogenated, resulting in co-adsorbed O* and OH* species. Water formation was found to be the potential-limiting step on all catalysts. The activity for the oxygen reduction reaction was evaluated against the difference of the oxygen adsorption energy on the Pt site and the M site of Pt3M and the results indicate that the oxygen adsorption energy difference offers an improved prediction of the oxygen reduction activity on these catalysts. Based on the analysis, Pt3Ni supported on oxygen-doped graphene exhibits an enhanced catalytic performance for oxygen reduction over Pt4.

PtPd Hybrid Composite Catalysts as Cathodes for Proton Exchange Membrane Fuel Cells

In this work, PtPd hybrid cathodic catalysts were prepared for a proton exchange membrane fuel cell (PEMFC) application by two different strategies. The first strategy was the physical mixing of bimetallic PtPd onto partially reduced graphene oxide (PtPd/rGO) and PtPd onto multi-walled carbon nanotubes (PtPd/MWCNT); (PtPd/rGO) + (PtPd/MWCNT). The second strategy was physical mixing of both carbonaceous supports before the PtPd deposition to form PtPd/(rGO:MWCNT). Our experimental results revealed that the PtPd nanomaterial prepared over a mixture of both carbonaceous supports had better oxygen reduction reaction (ORR) and PEMFC performances than the individually prepared catalysts. The insertion of MWCNT between rGO sheets prevented their stacking. This promoted the diffusion of oxygen molecules through the interlayer spacing, enhancing the ORR’s electrocatalytic activity. The durability test demonstrated that the hybrid supporting material dramatically improved the catalyst’s stability even after 3000 reaction cycles. This highlighted an increase greater than 100% for hybrid nanocomposites in their electrocatalytic activity as compared with the PtPd/rGO nanocomposite.