Xiuna Wang

Efficient dye-sensitized solar cells based on an iodine-free electrolyte using L-cysteine/L-cystine as a redox couple

A new iodine-free electrolyte based on amino acids L-cysteine/L-cystine as a redox couple has been designed and synthesized. DSSCs fabricated with the conventional I−/I3− redox couple gave efficiencies of 8.1% and 6.3% under optimized experimental conditions based on ruthenium dye, N719, and metal-free organic dye, TH202, respectively. Based on the same dyes, the DSSCs employing the new L-cysteine/L-cystine redox couple showed comparable efficiencies of 7.7% and 5.6%, respectively. However, higher incident-photon-to-electron (IPCE) conversion efficiencies and larger Jsc values were found for devices with the L-cysteine/L-cystine redox couple than with I−/I3−. From an electrochemical impedance spectroscopic study, we found that the charge recombination between the conduction band electrons in the TiO2 film and the electrolyte containing the L-cysteine/L-cystine redox couple is restrained.

Molecular Design to Improve the Performance of Donor–π Acceptor Near‐IR Organic Dye‐Sensitized Solar Cells

A novel near-IR charge-transfer complex, as a D-π-A-type mol., has a lateral anchoring group and a flexible long carbon chain that replaces the Me group of the donor part of the mol. This carbon chain seems to prevent the formation of mol. aggregates on the semiconductor (TiO2) nanoparticles, thus blocking charge recombination at relatively high open-circuit voltages and short-circuit photocurrent densities. This sensitizer dye has a max. IPCE (incident-photon-to-current conversion efficiencies) of 93% at 660 nm and an overall solar-energy-to-electricity conversion efficiency of 5.1%.

Photocatalytic Water Reduction and Study of the Formation of FeIFe0 Species in Diiron Catalyst Sytems

Noble-metal-free systems with bio-inspired diiron dithiolate mimics of the [FeFe]-hydrogenase active site, namely, [(μ-pdt)Fe(2) (CO)(5) L] [pdt=propanedithiolate; L=P(CH(2) OH)(3) (1), P(CH(3) )(3) (2)], as water reduction catalysts with xanthene dyes as photosensitizers and triethylamine as a sacrificial electron donor were studied for visible-light-driven water reduction to hydrogen. These systems display good catalytic activities with the efficiencies in hydrogen evolution of up to 226 turnovers for 1, if Eosin Y was used as the photosensitizer in an environmentally benign solvent (EtOH/H(2) O) after 15 h of irradiation (λ>450 nm) under optimal conditions. Under all of the conditions adopted, 1 that has a water soluble phosphine ligand, P(CH(2) OH)(3) displayed a higher efficiency than 2, which bears a PMe(3) ligand. The photoinduced electron transfer in the systems was studied using fluorescence, transient absorption, time-resolved UV/Vis, and in situ electron paramagnetic resonance (EPR) spectroscopy. A new electron-transfer mechanism is proposed for hydrogen evolution by these iron-based photocatalytic systems.

Efficient Organic Sensitizers with Pyridine‐N‐oxide as an Anchor Group for Dye‐Sensitized Solar Cells

Five organic dyes with pyridine-N-oxide as the anchor group and electron acceptor have been synthesized and applied in dye-sensitized solar cells (DSSCs). Benzothiadiazole was introduced in the conjugation system to increase the electron withdrawing properties, FTIR spectra showed that the coordination was between the pyridine-N-oxide and the Brønsted acid site on the TiO2 surface. The relationship between different dye structures and the performance of the DSSCs was investigated systematically. The location of the thiophene unit was studied, and the direct linkage of benzothiadiazole with pyridine-N-oxide was beneficial to broaden the absorption. The donor-acceptor-acceptor-configured dye WL307, which has 2-ethylhexyloxy chains in the donor part, showed the best efficiency of 6.08% under 100 mW cm(-2) light illumination. The dye series showed a fairly good stability during the one month test period.

Quick synthesis of nano-scale TS-1 and its catalytic properties

Abstract Nano-scale TS-1 was successfully synthesized through the modification of the conventional synthesis method. The effects of synthesis conditions (crystallization time, temperature and alcohol removal temperature) were investigated in detail. Moreover, the effect of surfactant was also studied. The results show that high quality TS-1 with crystal size of ca. 100 nm was obtained when the crystallization time was about 12 h; High crystallization temperature and alcohol removal temperature favor the incorporation of titanium into the framework. The addition of nonionic surfactant decreases the usage of template TPAOH and makes the crystal size of TS-1 more uniform. Using epoxidation of propylene and hydroxylation of phenol with dilute H 2 O 2 as the test reactions, the catalytic properties of TS-1 were investigated. The results show that nano-scale TS-1 exhibits high performance in the propylene epoxidation; after 300 h reaction, both the conversion of H 2 O 2 and the selectivity to PO are about 96%.

Propylene epoxidation over Ag/Ts-1 catalysts

Abstract Epoxidation of propylene to propylene oxide over Ag/TS-1 in the presence of oxygen and hydrogen was carried out in a fixed-bed, quartz flow reactor. The effects of Ag loading, support, Si/Ti mol ratio of TS-1 and calcination temperature of Ag/TS-1 on the propylene epoxidation were investigated. The results show that Ag loading, support and the calcination temperature of Ag/TS-1 as well as the Si/Ti mol ratio of TS-1 have a great effect on the catalytic properties. The optimum Ag loading, calcination temperature of Ag/TS-1 and Si/Ti mol ratio of TS-1 are 2wt%, 450°C and 64, respectively. Over 2.0wt%Ag/TS-l (n Si /n Ti =64) catalyst, at a space velocity of 300011 1 , 0.92% propylene conversion with 91.2% selectivity to propylene oxide is obtained at 150°C. The deactivation of Ag/TS-1 catalyst is not due to the changes of active species, but the coke of the catalyst, which can be easily regenerated by calcination at 450°C in air.