Applying a carbon coating to a non-conductive nanoporous ceramic makes it possible to use it as a conductive electrode while maintaining its shape. In the case of mesoporous silica (MPS), the silica surface can be completely covered with one or two layers of graphene by CVD using the catalytic effect of Si radicals. Similarly, nitrogen-doped carbon can be applied using a nitrogen-containing organic gas as the carbon source. Analysis of the effects of nitrogen doping using water-based capacitor measurements with carbon-coated MPSs (C-MPS) shows that the pseudocapacitance increase caused by doping corresponds to the number of pyridine-derived nitrogen atoms in the carbon film. A carbon-coated anodic aluminum oxide (C-AAO) film has aligned nanopores between the front and back surfaces, which provide a very good diffusion path for other materials. We have developed an electrode in which redox enzymes are immobilized in an orientation favorable to the electrocatalytic reaction by utilizing the electrostatic interaction between the enzyme and the C-AAO film. In the case of a biocathode with laccase immobilized on a C-AAO film, the reaction efficiency of the electrode prepared by controlling the enzyme orientation by applying a voltage of +0.65 V to the C-AAO film in the pH 5.0 solution was 1.5 times that of an electrode prepared using only physical adsorption.

Thermoelectric (TE)-based energy harvesting is an important aspect of modern and future power-generation technologies used to drive different types of sensors and wireless communication devices. Single-wall carbon nanotubes (SWCNTs), with a narrow bandgap energy and high charge-carrier mobility, are promising TE materials. They can be integrated into flexible TEs that can be used to recover waste heat. The recent development of TE materials based on SWCNTs is described. Sorting the SWCNTs into different structures to elucidate structure-property relationships, and chemical doping to change the TE properties are the major challenges in this field. Chemical techniques that address these issues have enabled the development of CNT-based thermoelectric generators.

High utilization efficiencies of hybridized redox-active materials are of great importance for increasing the capacitance of electrochemical capacitor electrodes. Herein, a redox-active alkylbenzoquinone, tetramethyl-1,4-benzoquinone (TMBQ), is hybridized in the gas phase in activated carbon (AC) pores with sizes of ∼4 nm, and the electrochemical capacitor performance of the obtained hybrids is evaluated using aqueous 1 M H₂SO₄ as electrolyte. The amount of hybridized TMBQ investigated herein is 4–10 mmol per gram of AC, and the utilization efficiencies of TMBQ in the resulting AC/TMBQ hybrids are ≥85%. The hybridization is not associated with the volume expansion of the AC particles, and therefore, the volumetric capacitance of the hybrids increases with increasing amount of TMBQ. Consequently, 1 mmol of TMBQ per gram of AC afforded the volumetric capacitance of ∼50 F cm⁻³ and the volumetric capacitance of the hybrid containing 10 mmol of TMBQ per gram of AC was 581 F cm⁻³ at the current density of 0.2 A g⁻¹, which is significantly higher than the volumetric capacitance of pristine AC (i.e., 99 F cm⁻³). Moreover, despite the substantial contribution of the reversible redox reaction of TMBQ to the increase in the capacitance, capacitance retentions of the hybrids up to a TMBQ amount of 8 mmol per gram of AC were higher at 10 A g⁻¹ than that of AC. The gas-phase adsorption does not require any organic solvents, concomitant solvent removal, or the drying process, and enables complete adsorption of TMBQ for the TMBQ amounts below the saturation capacity of AC. Therefore, this hybridization method is promising not only for enhancing the electrochemical capacitor performance but also for waste minimization.

Polydivinylbenzene (PDVB) was hybridized in the nanosized pores of activated carbon (AC) via radical polymerization. The amount of PDVB was varied by changing the adsorbed amount of divinylbenzene (DVB). DVB was adsorbed in the AC pores with sizes of <4 nm without using any organic solvents. The DVB-adsorbed AC was mixed with a radical initiator, 2,2′-azobisisobutyronitrile (AIBN), and the mixture was heated for polymerization. Unpolymerized DVB and AIBN-derived impurities were removed from the resulting AC/PDVB hybrids through vacuum heating. The absence of PDVB on the outer surface of the AC particles was verified through scanning and transmission electron microscopies. Nitrogen adsorption/desorption measurements of the hybrids revealed that their specific surface areas as well as micro- and mesopore volumes linearly decreased with increasing amount of hybridized PDVB. The electric double-layer capacitor performance of AC/PDVB hybrids was evaluated through electrochemical measurements in an aqueous H₂SO₄ as the electrolyte. The results revealed that their capacitances and rate capabilities decreased with increasing amount of hybridized PDVB. Further, they suggested that the hybridized PDVB exists as agglomerates distributed uniformly in the micropores and mesopores irrespective of the amount of PDVB.

The structure of carbon materials and their precursors can be studied by magic-angle spinning solid-state nuclear magnetic resonance (MAS-SS-NMR). The state and structure of adsorbed and/or intercalated molecules and ions on/in the carbon materials can also be determined using this method. Eddy currents induced by the magnetic field during measurements cause a temperature increase in conducting carbon materials. The effects of various physical and chemical characteristics of the carbon materials on this temperature increase were investigated. The oxygen content was found to be the dominant factor determing the temperature increase, with a higher oxygen content giving a smaller temperature increase. This correlation enables a rough estimate of the temperature increase in carbon materials prior to performing MAS-SS-NMR measurements.