Anchored Pt-Co Nanoparticles on Honeycombed Graphene as Highly Durable Catalysts for the Oxygen Reduction Reaction

Durability is an important factor in evaluating the performance of a catalyst. In this work, the spatial protection of the carrier to nanoparticles was considered to improve the durability of the catalyst. It is found that a honeycombed graphene with a three-dimensional (3D)-hierarchical porous structure (3D HPG) can help to reduce the shedding of Pt-Co nanoparticles (Pt-Co NPs) because 3D HPG can form a protective layer to reduce the direct erosion of Pt-Co NPs on the interface by an electrolyte. Then, appropriate oxygen groups were introduced on the 3D reduced hierarchical porous graphene oxide (3D rHPGO) to improve the dispersion of Pt-Co NPs on the surface of the carrier. It was found that the Pt d-band of the catalyst was anchored by π sites of carbonyl of an oxygen group. After optimization, the catalyst (referred to as Pt-Co/3D rHPGO) achieved a 2-fold enhancement in mass activity than that of a commercial Pt/C catalyst. More importantly, after the accelerated durability test (ADT) of 20 000 cycles, the Pt-Co/3D rHPGO catalyst can almost sustain this level of performance, whereas other catalysts showed a comparatively large loss of activity. According to the results, the high durability of Pt-Co/3D rHPGO was attributed to spatial protection of Pt-Co NPs and the defects on the surface allowed the electrolyte to enter. In addition, oxygen groups provided an anchoring effect on nanoparticles. Thus, the Pt-Co/3D rHPGO electrocatalyst exhibited splendid durability, holding a potential to be applied in PEMFC for long-term work.