A pyrene dimer (PYD) is synthesized by electrochemical oxidation via homocoupling of pyrene (PY) inside the pores of MgO-templated mesoporous carbons without any metal catalysts or organic solvents. The resulting MgO-C/PYD hybrids can be used as high-performance aqueous electrochemical capacitor electrodes due to the reversible redox property of PYD and large contact area between the hybridized PYD and conductive carbon surfaces, which enable rapid charge transfer at the large contact interface. In our previous study, PY was considered to polymerize through electrochemical oxidation, and activated carbon with the pore sizes of ∼4 nm was used as a porous carbon substrate. In this study, the MgO-templated carbons have the average pore sizes of 5, 10, and 30 nm, and their large mesopore volumes can accommodate a large amount of PYD for enhancing the capacitance. To develop high-performance electrochemical capacitors, the dependence of the capacitance enhancement and the capacitance retention on the amount of PY and the pore sizes of MgO-templated carbons are studied. It is found that mesopores are necessary for fast charging/discharging, but the capacitance retention and capacitance enhancement decrease with increasing the mesopore sizes and the amount of PY due to the decreased utilization ratio of PY.

Dye-sensitized solar cells composed of a photoanode of Ag nanoparticle (NP)-deposited TiO2 nanotube (TNT) arrays were fabricated. The TNT arrays were prepared by anodizing Ti films on fluorine-doped tin oxide (FTO)-coated glass substrates. Efficient charge transportation through the ordered nanostructure of TNT arrays should be carried out compared to conventional particulate TiO2 electrodes. However, it has been a big challenge to grow TNT arrays on FTO glass substrates with the lengths needed for sufficient light-harvesting (tens of micrometers). In this work, we deposited Ag nanoparticles (NPs) on the wall of TNT arrays to enhance light-harvesting property. Dye-sensitized solar cells with these Ag NP-deposited TNT arrays yielded a higher power conversion efficiency (2.03 %) than those without Ag NPs (1.39 %).PACS codes06.60.Ei Sample preparation, 81.05.Bx Metals, Semimetals, Alloys, 81.07.De Nanotubes

We report on a macroscopic study on the behavior of spillover H atoms using carbon black-supported Pt nanoparticles (CB/Pt) and various organic compounds adsorbed by microporous activated carbon (AC). The organic compound-adsorbed ACs are mixed with CB/Pt, and the mixtures are exposed to H2 at 25 °C. Therein, H2 molecules dissociatively adsorb onto the Pt nanoparticles, and H atoms spill over from the Pt nanoparticles to the CB particles. Subsequently, the H atoms undergo secondary spillover from the CB to the AC particles and diffuse inside the organic compound-filled micropores of the AC. From the results obtained, at least 1430 H atoms spill over from one Pt nanoparticle per second (5.15 million H atoms in 1 h). The spillover H atoms readily react with the unconjugated CC groups inside the AC pores. The H atoms also react with CO groups; however, the reactivities of the CC and CO groups are significantly decreased by extending the π-conjugation system. Meanwhile, H atoms do not react with many other oxygen-containing functional groups or polycyclic aromatic hydrocarbons. These results suggest that hydrogen storage capacities using hydrogen spillover may be overestimated by the irreversible reactions of spillover H atoms with the aforementioned functional groups when using chemically treated carbon-based materials (e.g., graphene oxide), owing to the existence of many functional groups.

Polydivinylbenzene (PDVB) is hybridized inside nanosized pores of activated carbon (AC) via radical polymerization. The amount of PDVB is varied by changing the adsorbed amount of divinylbenzene (DVB). The pore size of AC is less than 4 nm and DVB is adsorbed inside the AC pores without any organic solvents. The DVB-adsorbed AC is mixed with a radical initiator, 2,2'-azobisisobutyronitrile (AIBN), and the mixture is heated for polymerization. Unpolymerized DVB and AIBN-derived impurities are removed from the resulting AC/PDVB hybrids by vacuum heating. Absence of PDVB on the outer surface of AC particles is confirmed by scanning and transmission electron microscopies. A nitrogen adsorption/desorption measurement of the hybrids show that their specific surface areas as well as micro-and mesopore volumes linearly decrease with increasing the amount of the hybridized PDVB. Their electric double-layer capacitor (EDLC) performance is evaluated by electrochemical measurements using aqueous H2SO4 electrolyte. The results reveal that their capacitances and rate capabilities decrease with increasing the amount of the hybridized PDVB. These results suggest that the hybridized PDVB exist as agglomerates uniformly inside micropores and mesopores despite the amount of PDVB.

Dye-sensitized solar cells composed of a photoanode of Ag nanoparticle (NP)-deposited TiO 2 nanotube (TNT) arrays were fabricated. The TNT arrays were prepared by anodizing Ti films on fluorine-doped tin oxide (FTO)-coated glass substrates. Efficient charge transportation through the ordered nanostructure of TNT arrays should be carried out compared to conventional particulate TiO 2 electrodes. However, it has been a big challenge to grow TNT arrays on FTO glass substrates with the lengths needed for sufficient light-harvesting (tens of micrometers). In this work, we deposited Ag nanoparticles (NPs) on the wall of TNT arrays to enhance light-harvesting property. Dye-sensitized solar cells with these Ag NP-deposited TNT arrays yielded a higher power conversion efficiency (2.03 %) than those without Ag NPs (1.39 %).