Nitrogen Doped Carbon Electrodes—Influence of Microstructure and Nitrogen Configuration on the Electrical Conductivity of Carbonized Polyacrylonitrile and Poly(ionic liquid) Blends

Nitrogen doping in carbonaceous materials has been proven to modifiy the electronic structure and improve the electrical conductivity. [1] In this presentation, the preparation of nitrogen-doped carbon fibers and thin films from mixtures of polyacrylonitrile (PAN) and a poly(ionic liquid) (PIL) by electrospinning and dip-coating is presented, respectively, followed by carbonization at distinct temperatures. It is shown that the poor processability of the PIL into sub-micrometer fibers by electrospinning—originating from its high charge density and meanwhile low glass transition temperature—is successfully circumvented by using blends of PAN and PIL. The electrospun fiber mats exhibit a high surface-to volume-ratio with an intrinsically macroporous through-pore structure and a uniform fiber diameter after carbonization. Thorough physicochemical characterization of the N-doped carbons by means of scanning electron microscopy, algorithmic X-Ray diffraction analysis and fitting, nitrogen physisorption, thermogravimetry, elemental analysis, energy-dispersive X-ray, and X-ray photoelectron spectroscopy gives insight into their physical and electrical structures. Impedance measurements on carbonized PIL/PAN-blends reveal high electrical conductivities up to 320 S cm⁻¹, which are assigned to the incorporation of predominantly quaternary-graphitic nitrogen atoms into the carbon network during carbonization. The results indicate that the electrical conductance of the N-doped carbons strongly depends on the chemical environment of the inserted nitrogen atoms, the microstructural evolution of π-conjugated carbon network and the chemical composition. [2]<br/><br/>[1] Czerw, R., et al. "Identification of electron donor states in N-doped carbon nanotubes." <i>Nano Letters</i> 1.9 (2001): 457-460.<br/>[2] Einert, Marcus, et al. "Nitrogen Doped Carbon Electrodes: Influence of Microstructure and Nitrogen Configuration on the Electrical Conductivity of Carbonized Polyacrylonitrile and Poly (ionic liquid) Blends." <i>Macromolecular Chemistry and Physics</i> 216.19 (2015): 1930-1944.