Raman spectra of carbon nanowalls (CNWs) grown using dc plasma-enhanced chemical vapor deposition were analyzed. The Raman spectra of CNWs exhibited G and D bands at ∼1580 and ∼1350cm−1, respectively. It is found that the bandwidth of the G band is relatively narrow, even when the peak intensity ratio of D band to G band is significantly high. This spectral feature of CNWs is distinguished from those of typical graphitelike carbons reported so far. From the comparison of these spectral features, it is shown that CNWs are composed of small crystallites with a high degree of graphitization.

The nanostructure of carbon nanowalls ͑CNWs͒, composed of a stack of several graphite sheets, was investigated by transmission electron microscopy. Our detailed analysis revealed that numerous graphite regions with an average size of about 20 nm were formed in the CNWs. The formation of these regions originates from the introduction of lattice defects such as dislocations and the slight rotation of the graphite sheets. On this basis, it is concluded that the graphite regions, so-called "nanographite domains," are the constitutional units of the CNWs.

No abstract

Platinum catalysts supported on carbon nanowalls (Pt/CNW) were prepared by a solution-reduction method. It is shown that Pt nanoparticles with a mean diameter of 3.5 nm are well dispersed along domain boundaries in each CNW. In addition, it is shown that the Pt/CNW has high electrochemical active surface area and utilization, comparable to those for commercially available T–Pt/CB with good performance. Such high electrocatalytic activity could be attributed to the high electric conductivity of CNW and the improvement of electronic properties of Pt nanoparticles on the domain boundaries, in addition to the high dispersion of Pt particles.