Electrochemical CO2 reduction with low overpotential by a poly(4-vinylpyridine) electrode for application to artificial photosynthesis.

Pyridine molecules have been used as a catalyst to reduce the activation energy of the CO2 reduction reaction. It has been reported that CO2 is reduced by pyridine catalysts at low overpotential around -0.58 V vs. SCE. Poly(4-vinylpyridine), which has pyridine functional groups shows similar catalytic properties to reduce CO2 at low overpotential like pyridinium catalysts. Different thickness of P(4-VP) coated Pt electrodes were analyzed to determine the catalytic properties for CO2 reduction. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy methods showed the catalytic CO2 reduction properties of a P(4-VP)/Pt electrode. Thin P(4-VP)/Pt film showed a low current density of -0.16 mA cm-2 under CO2 atmosphere and the current density reached -0.45 mA cm-2 with increase of the P(4-VP) thickness. The increase of current density was explained by an increased surface concentration of adsorbed pyridinium groups of the thick P(4-VP) layer. Nyquist plots also showed decrease of impedance with increase of the P(4-VP) layer indicating fast charge transfer between Pt and the P(4-VP) layer due to the increase of hybrid ionic complex formation on the Pt surface. However, charge transfer is restricted when the P(4-VP) layer becomes more thick because of slowed protonation of pyridine groups adjacent to the Pt surface due to the suppressed permeability of electrolyte solution into the PVP membrane. This electrochemical observation provides a new aspect of P(4-VP) polymer for CO2 reduction.

Enhanced photocurrent density of hematite thin films on FTO substrates: effect of post-annealing temperature.

Fluorine doped tin oxide (FTO) is widely used as a substrate in the synthesis of a photo-reactive semiconductor electrode for solar water splitting. The hematite film on the surface of the FTO substrate annealed at 700 °C showed an enhanced photocurrent value with a maximum photocurrent of 0.39 mA cm(-2) at 1.23 V vs. RHE under 1 sun illumination. This is a much enhanced photocurrent value of the hematite films than that of those annealed at temperatures lower than 700 °C. This is a promising approach for the enhancement of the photoelectrochemical properties of metal oxide thin films. This work reports on the mechanism of the annealing process of the synthesized hematite film to enhance the photocurrent value. Furthermore, this can be used for the enhanced efficiency of the solar water splitting reaction.

Synergistic Interaction between Ruthenium Catalysts and Grafted Niobium on SBA-15 for 2,5-Furandicarboxylic Acid Production Using 5-Hydroxymethylfurfural.

This study entailed the synthesis of Ru nanocatalyst decorated on Nb-grafted SBA-15. A Nb-grafted SBA-15 support with varying Nb contents was utilized as a support for the Ru nanoparticles. The effect of Nb grafting on the immobilized Ru nanoparticle catalyst was systematically investigated, and its catalytic performance in the synthesis of furandicarboxylic acid using 5-hydroxymethylfurfural under base-free reaction conditions was evaluated. The results indicate the increased productivity of the Ru@Nb-grafted SBA-15 catalyst with a yield exceeding 95%, representing a significant advancement in catalysis. This study also affords insights into the complex relationship between the catalytic activity and selectivity and its unique surface attributes. Moreover, acidic sites were created, and the electron density within the active sites was modulated by monomeric Nb oxide species on the SBA-15. Additionally, the role of high-electron-density Ru atoms in facilitating the efficient adsorption and activation of the reactant, resulting in enhanced catalytic efficacy, was highlighted.

Enhanced Efficiency of Functional Smart Window with Solar Wavelength Conversion Phosphor-Photochromic Hybrid Film.

Here, the high sensitivity and enhanced photochromic efficiency of the hybrid film of solar wavelength conversion phosphor and photochromic film for functional smart window have been achieved by fabricating a double-layered hybrid structure of wavelength conversion phosphor and photochromic film. Y2SiO5:Pr3+ phosphor nanoparticles, which upconvert visible light to UV light, were synthesized by simple hydrothermal method. The synthesized Y2SiO5:Pr3+ nanoparticle was coated as layered structured film on photochromic H3PW12O40 film. The Y2SiO5:Pr3+/H3PW12O40 hybrid film showed an enhanced sensitivity and efficiency of photochromic process with solar light irradiation due to the increased UV portion of solar light through upconversion process of visible light by wavelength conversion phosphor layer. The increased UV portion by upconversion process of Y2SiO5:Pr3+ layer through excited-state absorption and energy transfer upconversion process, contributed to an enhancement of coloration rate of photochromic H3PW12O40 film by 7 times with 50 min of 1 sun irradiation due to fast conversion of W6+ state to W5+ state in H3PW12O40 film with 5 times enhanced photochromic sensitivity compared with pristine photochromic film.

Photoelectrochemical Activity of Sodium Titanate Nanobelts for Photoanode.

We report photoelectrochemical characteristics of sodium titanate nanobelts as a photoanode. Sodium titanate nanobelts were synthesized by hydrothermal process using titanium(IV) tetrabutoxide in a concentrated aqueous NaOH solution. The formation mechanism of sodium titanate nanobelts in the synthetic process has been comparatively studied on the control of reaction time, pH and concentration of precursors, etc. The morphology and optical property have been investigated with X-ray diffraction, scanning electron microscope, transmission electron microscope, and ultraviolet-visible spectroscopy. On the basis of their morphological and optical characteristics, sodium titanate nanobelts were applied for photoelectrochemical cell as working electrode. After transparent film of sodium titanate nanobelts is formed on the fluorine-doped tin oxide (FTO) glass by doctor blade technique, the photoelectrochemical results were discussed on the structure of photoanode of dye sensitized solar cells.

Manual assembly of nanocrystals for enhanced photoelectrochemical efficiency of hematite film.

To improve the optoelectronic properties of hematite film as a photoanode, hematite film was orientated on the (012) plane by the secondary growth of organized microcrystals. The resultant film showed promising photoelectrochemical effects compared with a randomly oriented one, with a maximum photocurrent of 0.8 mA cm(-2) at 1.23 V vs. RHE under the illumination of 1 sun.