Yue Guan,Zhiyu Dou,Yan Yang,Juanhong Xue,Zhen Zhu,Lili Cui
We have synthesized hierarchically 3D porous Fe5C2/N-doped graphene (3D Fe5C2/N-PG) with numerous micro/meso-pores by a controllable and facile strategy. The density of the micro/meso-pores can be accurately tailored by adjusting the reaction conditions. It is found that the ORR performance of the electrocatalyst is strongly dependent on the pore structures under the same conditions. The electrocatalyst exhibits comparable activity in an acidic solution together with superior activity in an alkaline solution to the state-of-the-art Pt/C catalyst in terms of onset potential, half-wave potential, diffusion-limiting current density and kinetic current density. The excellent electrocatalytic activity is attributed to the balance of the surface area, hierarchical porosity, chemical composition (pyridinic N, graphitic N and Fe5C2 nanoparticles) and conductivity of the 3D interconnected graphene. This strategy for the tunable synthesis of hierarchically 3D porous graphene materials offers a platform for developing catalysts with superior activity in energy devices.
Bo Jiang,Wang Yang,Hengxuan Bai,Chaonan Wang,Chong Xu,Zhengxuan Li,Lu Yan,Chengxiao Zhang,Ni Wu,Sai Che,Xiaobai Wang,Yongfeng Li
The challenge of realizing low filler loading and high-performance microwave absorbing (MA) materials is still an urgent issue to be solved. Herein, porous N-doped carbon wrapped Fe/Fe 5 C 2 (Fe/Fe 5 C 2 @NC) nanocomposite is successfully synthesized by a facile one-step calcination of carbon nitride and ferrocene precursors. The magnetic Fe/Fe 5 C 2 nanoparticles are tightly and uniformly anchored on the wrinkled carbon nanosheets . Abundant of voids exist between the three-dimensional conductive carbon network, which can result in a low density and a strong interfacial polarization relaxation with effect. Based on the double attenuation mechanisms of dielectric loss and magnetic loss, the optimized Fe/Fe 5 C 2 @NC-800 possesses a minimum reflection loss value reaching −63.1 dB and an effective absorption bandwidth (EAB) as broad as 7.3 GHz with an extremely low filler loading of 4 wt%. The Fe/Fe 5 C 2 @NC-800 can even achieve a broad EAB within 4.5–18.0 GHz by tuning the absorber thickness in the range of 2.5–5.0 mm, covering nearly 85% of the whole measured frequency band. This work provides new insights for the development of advanced lightweight MA materials, which has wide effective absorption frequency range and strong absorption intensity at low filling levels.
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