Steven S. C. Chuang

Enhanced Thermoelectric Properties of Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) by Binary Secondary Dopants.

UNLABELLEDnTo simultaneously increase the electrical conductivity and Seebeck coefficient of poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (nnnPEDOTnPSS) was a challenge for realizing efficient organic thermoelectrics. In this study, for the first time, we report both increased electrical conductivities and Seebeck coefficients, hence, enhanced thermoelectric properties ofnnnPEDOTnPSS thin films by doped with binary secondary dopants, dimethyl sulfoxide (DMSO) and poly(ethylene oxide) (PEO). Without modifying film morphology, the molar ratios of PEDOT to PSS are tuned by PEO, resulting in increased proportions of PEDOT in the bipolaron states. Our study provides a facile route to optimizing thermoelectric properties ofnnnPEDOTnPSS thin films.

Effects of Magnetic Nanoparticles and External Magnetostatic Field on the Bulk Heterojunction Polymer Solar Cells

The price of energy to separate tightly bound electron-hole pair (or charge-transfer state) and extract freely movable charges from low-mobility materials represents fundamental losses for many low-cost photovoltaic devices. In bulk heterojunction (BHJ) polymer solar cells (PSCs), approximately 50% of the total efficiency lost among all energy loss pathways is due to the photogenerated charge carrier recombination within PSCs and low charge carrier mobility of disordered organic materials. To address these issues, we introduce magnetic nanoparticles (MNPs) and orientate these MNPS within BHJ composite by an external magnetostatic field. Over 50% enhanced efficiency was observed from BHJ PSCs incorporated with MNPs and an external magnetostatic field alignment when compared to the control BHJ PSCs. The optimization of BHJ thin film morphology, suppression of charge carrier recombination, and enhancement in charge carrier collection result in a greatly increased short-circuit current density and fill factor, as a result, enhanced power conversion efficiency.

Solid oxide fuel cells fueled with reduced Fe/Ti oxide

For the first time, a Fe–Ti–O containing pellet, a viable chemical looping particle, was used as a solid fuel for direct contact with the Ni/YSZ anode surface of a solid oxide fuel cell. A maximum power density of 97 mW cm−2, corresponding to 84% of that in the H2 fuel, was produced using Fe–Ti–O in an inert Ar gas environment at 750 °C. The Fe–Ti–O pellets were able to generate stable electricity under repeated electrochemical oxidation and hydrogen reduction cycles. Temperature-programmed oxidation–reduction coupled with infrared spectroscopic studies revealed that the oxidation of the Fe–Ti–O pellet followed a shrinking core model; the reduction followed a progressive-conversion model. The ability of the Fe–Ti–O pellet to generate electricity on the Ni/YSZ surface can be attributed to its low resistivity (<17 Ω cm) which allows electrons to transport from the electrochemical oxidation sites to the anode surface. This study demonstrates that coupling a SOFC with an external reducer using Fe–Ti–O, an oxygen carrier, is a good candidate for electricity generation.

Silica-Supported Amine Catalysts for Carbon–Carbon Addition Reactions

Basic catalysts for carbon–carbon addition reactions were synthesized by immobilization of amine species on silica supports. Tetraethylenepentamine was impregnated and immobilized on amorphous silica (SiO2) and SBA-15 using an epoxy resin. The basicity of the catalysts was determined by adsorption–desorption of CO2 and the degree of immobilization was evaluated by FTIR. The catalytic activity towards the Claisen condensation reaction of methyl benzoate and methyl ethyl ketone was evaluated by an in-situ FTIR micro-scale reactor. A mechanism is proposed to show that the catalysts promote the formation of β-diketone and methanol; the effects of the support and amine immobilization degree are discussed.

In-Situ Infrared Study of the Synthesis of Polyaniline Under Acid and Neutral pH

In-situ infrared study of polyaniline (PANI) synthesis showed that the reaction initiated at pHxa0=xa01.5 produced a granule PANI microstructure via para-linked dimers of 4-aminodiphenylamine, exhibiting γ(C–H) at 802xa0cm−1; the reaction initiated at pHxa0=xa05.0 and 7.0 produce fiberous, and planar microstructures via ortho-linked dimers of 1,2-aminodiphenylamine and phenazine, exhibiting γ(C–H) at 738 and ν(C=N) at 1446xa0cm−1. The doped PANI that was produced at pH less than 5.0 showed a feature-less IR background absorption above 1600xa0cm−1. This absorption could correspond to π-electron delocalization as an indicative of polyaniline conductivity.

Porous Poly(vinyl alcohol) Composite Membranes for Immobilization of Glucose Oxidase

Particle loaded porous poly(vinyl alcohol) composite membranes were selected for immobilization of glucose oxidase (GOx) for their hydrophilicity and unique interactions with amino functional groups. GOx was immobilized on the membranes by adsorption at pH values between 3.5 and 7.1. The highest adsorption loading was observed at pH 7.1 and the highest catalytic activity was observed at pH 5.1. Infrared studies showed that the highest ratio of amide I to amide II at pH 5.1 is obtained for GOx immobilized on membranes loaded with amine-functionalized micro-particles, suggesting that the conformational changes of GOx on these membranes yield to higher catalytic activity than in other supports.

In Situ Pulse Diffuse Reflection Infrared Fourier Transform Spectroscopy (DRIFTS) Mass Spectrometry Study of the Water-Gas Shift Reaction on Nickel(II) Oxide-Zinc(II) Oxide Catalysts

The water-gas shift (WGS) reaction has been studied by pulsing carbon monoxide (CO) into a steady-state water (H2O)-Ar flow over nickel(II) oxide–zinc oxide (NiO–ZnO) catalysts using in situ diffuse reflection infrared Fourier transform spectroscopy (DRIFTS) coupled with a mass spectrometer method using the pulse technique (in situ pulse DRIFTS-MS) for different flow rates (gas hourly space velocity [GHSV] of 24 000–72 000 h−1) and reaction temperatures (250–350 °C). The results obtained from the in situ pulse DRIFTS-MS revealed that there are two types of water adsorption bands on the surface of the catalyst: (i) molecular adsorption (infrared [IR] bands in the 2500–3600 cm−1 range and at 1640 cm−1), and (ii) dissociative adsorption at 3700 cm−1, where carboxyl bands are formed at 1461 and 1368 cm−1 and the gas-phase CO is adsorbed at 2187 and 2111 cm−1 on the surface of the catalyst. After using a GHSV = 24 000 h−1 H2O/Ar flow, we probed the existence of two active intermediates via the formation of two hydrogen production peaks. The products of hydrogen gas (H2) and carbon dioxide (CO2) had two pathways: the redox process and the associative process via the intermediate of the carboxyl group. In situ pulse DRIFTS-MS proves to be an effective approach for studying the nature of adsorbed species on the catalyst surface and the nature of the reaction product.