Chunyong He

Nitrogen-self-doped graphene-based non-precious metal catalyst with superior performance to Pt/C catalyst toward oxygen reduction reaction

A new, simple and scalable synthesis methodology is invented for an N-self-doped graphene-based non-precious Fe catalyst (Fe–N-graphene) for the oxygen reduction reaction (ORR) both in acidic and alkaline media. The electrochemical characterization shows that this Fe–N-graphene catalyst possesses outstanding electrocatalytic ORR activity (similar to Pt/C catalyst in alkaline media and slightly lower in acidic media), and both superior stability and fuel (methanol and CO) tolerance to Pt/C catalysts. We believe that this is the first time for a non-precious metal catalyst to have superior ORR performance to Pt/C catalyst. In addition, our synthesis methodology can be scaled up for the mass production of N-self-doped graphene-based fuel cell non-noble metal catalysts and other nanomaterials.

A strategy for mass production of self-assembled nitrogen-doped graphene as catalytic materials

The mass production of graphene and nitrogen-doped (N-doped) graphene constitutes one of the main obstacles for the application of these materials. We demonstrate a novel resin-based methodology for large-scale self-assembly of the N-doped graphene. The N-doped graphene is readily obtained by using a precursor containing nitrogen and metal ions. The N-doped graphene is characterized by Raman, AFM, TEM, SEM, synchronic radiation and XPS measurements. The electrochemical performance of the catalyst made with such materials is investigated by a rotating ring-disk electrode (RRDE) system. The results reveal that the N-doped graphene is a selective catalyst and possesses an outstanding electrocatalytic activity, long-term stability, and good methanol and CO tolerance for oxygen reduction reaction (ORR).

Nitrogen-self-doped graphene as a high capacity anode material for lithium-ion batteries

Promising electrochemical energy conversion and storage devices constitute the main obstacles to the use of electrode materials of high energy and power density and long-cycling life to applications in lithium-ion batteries (LIBs). In this paper, we demonstrate a resin-based methodology for large-scale self-assembly of nitrogen-doped graphene (N-graphene), which has high capacity as an anode material for LIBs. The N-graphene is readily obtained using nitrogen- and metal ion-containing precursors. The N-graphene is characterized by Raman, AFM, TEM, SEM, and XPS measurements. It exhibits a very large reversible capacity of 1177 mA h g−1 at a current of 0.05 A g−1 as well as good cycling performance. The resulting N-graphene shows high capacity of 682 mA h g−1 over 95 cycles, representing a promising cathode material for rechargeable LIBs with high energy density. A good rate capability is also observed for N-graphene which exhibits large capacities of 540 and 443 mA h g−1 at large currents of 1 A g−1 and 2 A g−1, respectively. It is demonstrated that N-graphene can be a promising candidate for anode materials in high capacity LIBs.

Bimetallic PtAg alloyed nanoparticles and 3-D mesoporous graphene nanosheet hybrid architectures for advanced oxygen reduction reaction electrocatalysts

Herein, three-dimensional mesoporous graphene conductive networks supporting bimetallic PtAg alloyed nanoparticles (i.e. PtAg/3DMGS) with a superior composited nanostructure have been fabricated for advanced oxygen reduction reaction electrocatalysts. The unique architecture of 3D porous graphene exhibits a high surface area (1382 m2 g−1), a well-defined mesoporous structure (an average pore size of 3.28 nm), as well as an excellent electronic conductivity (1350 S m−1). Inside the PtAg/3DMGS, high-density and ultrafine PtAg NPs (∼2.5 nm) were well dispersed on the porous surface of 3DMGS. The combination of ultrafine PtAg NPs and 3DMGS conductive networks provides a relatively stable macroporous composite architecture, which offers convenient binary channels for both electron transport and ion diffusion. This promising PtAg/3DMGS composite material reveals an ultrahigh mass activity (at 0.9 V) of 392 mA mgPt−1, which is nearly 4 times that of Pt/C (TKK) (102 mA mgPt−1). After 1000 CV cycles, the retention rates of mass activity are 81.6% and 66.7% for PtAg/3DMGS and Pt/C (TKK), respectively. These results demonstrate that the PtAg/3DMGS composite material is a promising electrocatalyst with high catalytic activity and high stability for the oxygen reduction reaction.