Due to low density, extremely high electrical and thermal conductivities, graphene has great potential to construct lightweight thermal conductive paper for high-power electric devices. However, the remarkable properties of graphene are on a molecular level and difficult to achieve when processed into macroscopic paper. Here, an effective route to construct ultrahigh conductive graphene paper is developed. First, large-volume, high-concentration, planedefect-free, few-layer graphene dispersion is fast produced from graphite at high yield through ball milling. The exfoliated graphene dispersion is further processed into graphene paper through fast filtration, thermal treatment, and mechanical compression. The electrical and thermal conductivities of the resultant graphene paper are as high as 2231 S cm −1 and 1529 W m −1 K −1 , superior to previously reported graphene papers. Structural analyses confirm that the ultrahigh conductivities are attributed to high quality of graphene sheets, their compact ordered stacking, and large graphitic crystalline domain size, which improve electron and phonon transport within basal plane of graphene sheet and between graphene sheets.

The development of nonprecious-metal-based electrocatalysts with high oxygen reduction reaction (ORR) activity, low cost, and good durability in both alkaline and acidic media is very important for application of full cells. Herein, we developed a facile and economical strategy to obtain porous core-shell Fe3C embedded nitrogen-doped carbon nanofibers (Fe3C@NCNF-X, where X denotes pyrolysis temperature) by electrospinning of polyvinylidene fluoride (PVDF) and FeCl3 mixture, chemical vapor phase polymerization of pyrrole, and followed by pyrolysis of composite nanofibers at high temperatures. Note that the FeCl3 and polypyrrole acts as precursor for Fe3C core and N-doped carbon shell, respectively. Moreover, PVDF not only plays a role as carbon resources, but also provides porous structures due to hydrogen fluoride exposure originated from thermal decomposition of PVDF. The resultant Fe3C@NCNF-X catalysts, particularly Fe3C@NCNF-900, showed efficient electrocatalytic performance for ORR in both alkaline and acidic solutions, which are attributed to the synergistic effect between Fe3C and N-doped carbon as catalytic active sites, and carbon shell protects Fe3C from leaching out. In addition, the Fe3C@NCNF-X catalyst displayed a better long-term stability, free from methanol crossover and CO-poisoning effects than those of Pt/C, which is of great significance for the design and development of advanced electrocatalysts based on nonprecious metals.

A highly flexible all-solid-state symmetric supercapacitor using an aramid nanofibers/PEDOT:PSS (ANFs/PEDOT:PSS) film exhibits excellent energy density and cycling stability.