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For utilization in future electronic application of graphene materials, nitrogen (N) atom doping into graphene sheets is an important technology. We investigated the electrical conduction of carbon nanowalls (CNWs), consisting of stacks of graphene sheets standing vertically on substrates. By post-treatment for 30 s, the electrical conductivity of CNWs increased. On the other hand, as the post-treatment time increased, the electrical conductivity decreased. According to Hall measurement, the carrier density decreased with increasing post-treatment time, while the carrier mobility increased. Consequently, the electrical conduction of the CNWs was successfully controlled by N2 plasma treatment.

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For polymer electrolyte fuel cell applications, effects of Pt-nanoparticle-supported 3D carbon nanostructures, i.e. carbon nanowalls (Pt/CNWs), on electrochemical characteristics were determined by alternating current impedance analysis of resistive elements, which contribute to the oxygen reduction reaction. CNWs were fabricated by radical-injection plasma-enhanced chemical vapor deposition (RI-PECVD), and Pt catalysts were formed on the template of CNWs by supercritical fluid metalorganic chemical fluid deposition. CNWs of different wall densities were synthesized during RI-PECVD by varying the deposition pressure. The resistive elements can be consisted of three regions with different corresponding frequencies, and the resistive elements of mass diffusion, which showed up in the lowest frequency region of less than 100 Hz, increased as the wall density of CNWs increased. It was found that the wall density of CNWs was one of the essential parameters of Pt/CNWs for the electrochemical reaction involving the fluid flow and the mass transfer of active materials.