Structure-transport relationships in graphenated carbon nanotubes with hierarchical foliates for fundamental electrochemical applications

Graphenated carbon nanotubes (g-CNTs) provide a strategic solution to overcome the intrinsic charge- transport limitations of conventional carbon nanotube (CNT) electrodes by integrating one-dimensional nanotube backbones with two-dimensional graphene edge architectures. Here, we report a synthesis structure transport property study of lightweight g-CNT aerogels fabricated via floating catalyst chemical vapor deposition (FCCVD), where the precursor injection rate is used as a single, scalable parameter to control graphenation. A reduced injection rate promotes the in-situ growth of crumpled graphene foliates on CNT sidewalls, yielding a hierarchical three-dimensional network, while higher injection rates favour smooth, graphitic CNTs. Structural characterization reveals that g-CNTs exhibit increased disorder and reduced long-range graphitic order, evidenced by a broadened (002) XRD reflection (FWHM ≈ 1.30°) and higher Raman disorder ratios (ID/IG ≈ 1.13) relative to CNTs. Despite this disorder, g-CNTs display nearly double the bulk electrical conductivity (3.24 Scm⁻¹ vs. 1.64 Scm⁻¹), highlighting the role of graphene-mediated junction engineering rather than crystallinity alone. Rheological and morphological analyses further show that graphene foliates enhance interparticle connectivity, dispersion stability, and processability. Electrochemical impedance spectroscopy reveals that graphenation fundamentally reconfigures a junction-limited CNT network into a hybrid percolation system with parallel relaxation pathways. Notably, both junction and charge-transfer resistances are minimized at an optimal electrode thickness of 150 μm. Cyclic voltammetry independently validates the functional outcome of this transport optimization, with g-CNT electrodes delivering a four-fold higher specific capacitance and exhibiting a sharp maximum in areal capacitance (0.491 mF cm⁻²) precisely at the thickness corresponding to the impedance minimum. Our findings suggest that FCCVD-controlled graphenation utilizes structural disorder to facilitate kinetically efficient transport pathways. These results offer valuable insights for the design of advanced hierarchical carbon electrodes, suggesting that electrochemical performance is governed more by engineered connectivity than by simple surface area maximization.

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