• Energy Research

Abstract We report a proof-of-concept micro-spectroscopy, stochastic dynamics, and optical trapping study of a well-known reaction for methylene blue photodegradation catalyzed by titanium dioxide aggregates and nanotubes. Photocatalysis is performed under a high concentration of reactants and catalyst loading to characterize the fundamental chemical kinetics and dynamics aspects of this reaction under in operando conditions. We also report the effect of substrate concentration, light intensity, and substrate/catalyst ratio on the kinetic profiles. Optical imaging is used to quantify how spatial and concentration variations affect the reaction kinetics. To study the dynamics of individual nanoparticle catalysts under in operando conditions, we use optical trapping to characterize the stochastic dynamics of single TiO2 nanotubes. Overall, the results presented here indicate that the setup can be used to monitor photocatalytic degradation of methylene blue with simultaneous measurements of images and spectra while also monitoring the catalyst Brownian motion at the single-particle level.

Abstract We report a proof-of-concept micro-spectroscopy, stochastic dynamics, and optical trapping study of a well-known reaction for methylene blue photodegradation catalyzed by titanium dioxide aggregates and nanotubes. Photocatalysis is performed under a high concentration of reactants and catalyst loading to characterize the fundamental chemical kinetics and dynamics aspects of this reaction under in operando conditions. We also report the effect of substrate concentration, light intensity, and substrate/catalyst ratio on the kinetic profiles. Optical imaging is used to quantify how spatial and concentration variations affect the reaction kinetics. To study the dynamics of individual nanoparticle catalysts under in operando conditions, we use optical trapping to characterize the stochastic dynamics of single TiO2 nanotubes. Overall, the results presented here indicate that the setup can be used to monitor photocatalytic degradation of methylene blue with simultaneous measurements of images and spectra while also monitoring the catalyst Brownian motion at the single-particle level.

Abstract Dye-sensitized TiO2 solar cells assembled with a polymer electrolyte were investigated, aiming at the construction of an 8 V solar module. The individual solar cells were assembled with 4.5 cm2 active area and were characterized under outdoor conditions, exhibiting an average efficiency of 0.9% per cell (at 12:00 noon). The solar module was built by connecting 13 cells in series. The integrated average daily power was estimated to be 183 mW. The present paper discusses the performance of the individual cells and the module.

Abstract Dye-sensitized TiO2 solar cells assembled with a polymer electrolyte were investigated, aiming at the construction of an 8 V solar module. The individual solar cells were assembled with 4.5 cm2 active area and were characterized under outdoor conditions, exhibiting an average efficiency of 0.9% per cell (at 12:00 noon). The solar module was built by connecting 13 cells in series. The integrated average daily power was estimated to be 183 mW. The present paper discusses the performance of the individual cells and the module.

A little-studied p-type ternary oxide semiconductor, copper(I) tungstate (Cu2WO4), was assessed by a combined theoretical/experimental approach. A detailed computational study was performed to solve the long-standing debate on the space group of Cu2WO4, which was determined to be triclinic P1. Cu2WO4 was synthesized by a time-efficient, arc-melting method, and the crystalline reddish particulate product showed broad-band absorption in the UV-visible spectral region, thermal stability up to ∼260 °C, and cathodic photoelectrochemical activity. Controlled thermal oxidation of copper from the Cu(I) to Cu(II) oxidation state showed that the crystal lattice could accommodate Cu2+ cations up to ∼260 °C, beyond which the compound was converted to CuO and CuWO4. This process was monitored by powder X-ray diffraction and X-ray photoelectron spectroscopy. The electronic band structure of Cu2WO4 was contrasted with that of the Cu(II) counterpart, CuWO4 using spin-polarized density functional theory (DFT). Finally, the compound Cu2WO4 was determined to have a high-lying (negative potential) conduction band edge underlining its promise for driving energetic photoredox reactions.

A little-studied p-type ternary oxide semiconductor, copper(I) tungstate (Cu2WO4), was assessed by a combined theoretical/experimental approach. A detailed computational study was performed to solve the long-standing debate on the space group of Cu2WO4, which was determined to be triclinic P1. Cu2WO4 was synthesized by a time-efficient, arc-melting method, and the crystalline reddish particulate product showed broad-band absorption in the UV-visible spectral region, thermal stability up to ∼260 °C, and cathodic photoelectrochemical activity. Controlled thermal oxidation of copper from the Cu(I) to Cu(II) oxidation state showed that the crystal lattice could accommodate Cu2+ cations up to ∼260 °C, beyond which the compound was converted to CuO and CuWO4. This process was monitored by powder X-ray diffraction and X-ray photoelectron spectroscopy. The electronic band structure of Cu2WO4 was contrasted with that of the Cu(II) counterpart, CuWO4 using spin-polarized density functional theory (DFT). Finally, the compound Cu2WO4 was determined to have a high-lying (negative potential) conduction band edge underlining its promise for driving energetic photoredox reactions.

Dye-sensitized TiO2 solar cells, DSSC, are a promising alternative for the development of a new generation of photovoltaic devices. DSSC are a successful combination of materials, consisting of a transparent electrode coated with a dye-sensitized mesoporous film of nanocrystalline particles of TiO2, an electrolyte containing a suitable redox-couple and a Pt coated counter-electrode. In general, Ru bipyridyl complexes are used as the dye sensitizers. The light-to-energy conversion performance of the cell depends on the relative energy levels of the semiconductor and dye and on the kinetics of the electron-transfer processes at the sensitized semiconductor | electrolyte interface. The rate of these processes depends on the properties of its components. This contribution presents a discussion on the influence of each of the materials which constitute the DSSC of the overall process for energy conversion. An overview of the results obtained for solid-state dye-sensitized TiO2 solar cells assembled with polymer electrolytes is also presented.