The burgeoning demand for clean and energy-efficient fuel cell system requires electrocatalysts to deliver greater activity and selectivity. Bimetallic catalysts have proven superior to single metal catalysts in this respect. This work reports the preparation, characterization, and electrocatalytic characteristics of a new bimetallic nanocatalyst. The catalyst, Pt–Au–graphene, was synthesized by electrodeposition of Pt–Au nanostructures on the surface of graphene sheets, and characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray powder diffraction (XRD), and voltammetry. The morphology and composition of the nanocatalyst can be easily controlled by adjusting the molar ratio between Pt and Au precursors. The electrocatalytic characteristics of the nanocatalysts for the oxygen reduction reaction (ORR) and the methanol oxidation reaction (MOR) were systematically investigated by cyclic voltammetry. The Pt–Au–graphene catalysts exhibits higher catalytic activity than Au–graphene and Pt–graphene catalysts for both the ORR and the MOR, and the highest activity is obtained at a Pt/Au molar ratio of 2 : 1. Moreover, graphene can significantly enhance the long-term stability of the nanocatalyst toward the MOR by effectively removing the accumulated carbonaceous species formed in the oxidation of methanol from the surface of the catalyst. Therefore, this work has demonstrated that a higher performance of ORR and the MOR could be realized at the Pt–Au–graphene electrocatalyst while Pt utilization also could be greatly diminished. This method may open a general approach for the morphology-controlled synthesis of bimetallic Pt–M nanocatalysts, which can be expected to have promising applications in fuel cells.

Modulating the electronic characteristics of graphene is of great technological importance for improving and expanding its applications. Chemical doping with other elements is a promising way to achieve this goal. This work reports a facile synthesis of nitrogen-doped graphene (N-graphene) at low temperature. This method, which involves the steps of graphite oxidation, exfoliation, and chemical reduction with the use of hydrazine as a reducing agent, can simultaneously realize the reduction of graphene oxide and doping graphene with nitrogen atoms. The spectroscopic results demonstrate that N-graphene with N/C atomic ratio up to ∼4.5% can be prepared, and the doping N atoms consist of pyridinic, pyrrolic, graphitic, and oxidized nitrogen structures with the surface atomic compositions of ∼28%, 49%, 19%, and 4%, respectively. The prepared N-graphene exhibits superior electrocatalytic activity toward H₂O₂ reduction, and the contribution of the doped N atoms to the enhanced electrocatalytic activity is explained in detail based on density functional theory (DFT) calculations. Moreover, N-graphene is further used to study the dynamic process of H₂O₂ (a common representative of reactive oxygen species, ROS, in living cells) release from living cells such as neutrophil, RAW 264.7 macrophage, and MCF-7 cells. The results presented here open a new way to synthesize N-graphene, and also developed a new platform for a reliable collection of kinetic information on cellular ROS release. The approach established in this work could be potentially useful in study of downstream biological effects of various stimuli in physiology and pathology.