Embedding Pt-Ni octahedral nanoparticles in the 3D nitrogen-doped porous graphene for enhanced oxygen reduction activity

Abstract

Due to its better corrosion resistance and higher mechanical strength, 3D graphene is considered as a promising support for oxygen reduction reaction (ORR) electrocatalysts. However, the chemical inertness nature of graphene makes it difficult for Pt-based catalysts to anchor on. Compared with the spherical catalyst, although the Pt-based octahedral catalyst possesses higher mass activity (MA), it has fewer active sites per unit mass due to its larger size, which further hinders the application of 3D graphene as the support of Pt-based octahedral catalyst. Herein, we developed a facile and effective one-step hydrothermal method to fabricate nitrogen-doped porous graphene (NPG). The carbon material with an interconnected 3D framework and submicron macropores was then used to support Pt-Ni octahedral nanoparticles (NPs). The nitrogen not only increase the number of defects, but also improves the distribution of Pt-based octahedral catalysts on the graphene. The electrochemical surface areas (ECSA) of Pt-Ni/NPG reaches 5.5 times that before N-doping. Relative to commercial Pt/C (JM), Pt-Ni/NPG exhibits 6.8-fold enhancement in MA for 725.2 mA mgPt−1 at 0.9 VRHE. Particularly, Pt-Ni/NPG showed only 8.6% loss in MA after 8000 cycles of the accelerated durability test, as compared to a sharp decrease of 56.2% for Pt/C after only 4000 cycles. In the accelerated durability test of carbon support, Pt-Ni/NPG also exhibited good durability relative to Pt-Ni/C. These results indicate that the Pt-based octahedral catalyst supported on NPG is expected to be applied to proton exchange membrane fuel cells (PEMFCs).