Enhancement of Photocatalytic and Electrochromic Properties of Electrochemically Fabricated Mesoporous WO₃ Thin Films

Abstract

ExperimentalTetraethoxysilane (TEOS), nitric acid, surfactant, and 2,5-diiodothiophene were mixed in tetrahydrofuran (THF) at room temperature for half an hour to form a precursor solution. The catalytic complex was formed by reacting palladium acetate, cuprous iodide, and triphenylphosphine (PPh 3 ) in THF. A typical synthesis utilizes a molar ratio of reactants of THF/HNO 3 /TEOS/Brij-58/PPh 3 / CuI/Pd(OAc) 2 /2,5-diiodothiophene of 6.2:0.356:0.937:0.1:0.04:0.014:0.017:0.1, where Brij-58 is a non-ionic surfactant CH 3 (CH 2 ) 15 (OCH 2 CH 2 ) 20 OH. Films were prepared by either spin-coating the mixture of the catalytic complex and precursor solutions onto glass slides using a Specialty Coating Systems P-6000 spin-coater or allowing them to evaporate in a petri dish to form xerogels. The thin films were exposed to acetylene gas and triethylamine vapor at room temperature and 50 psi pressure for up to 3 days to polymerize the incorporated monomer. Pure conjugated PTE was obtained by washing with dilute HF to remove the silica and by ethanol extraction to remove the surfactant. The PTE was washed with ethanol to remove the unbound catalyst and partially dissolved in chloroform to achieve oligomeric PTE solutions that were subsequently coated on glass slides to form red oligomeric PTE films. The oligomeric PTE films were exposed to acetylene gas and the continuous reactions of acetylene with the active complex attached to the oligomers resulted in darkened films with increased UV-vis absorptions.The nanocomposites were characterized by transmission electron microscope (TEM, JEOL 2010, operated at 200 kV), X-ray diffraction (XRD, Phillips Xpert X-ray diffractometer using Cu Ka radiation at k = 0.1542 nm), UV-vis spectroscopy (Beckman DU460B UV-vis), Fourier transform infrared spectroscopy (FTIR, Thermo Nicolet Nexus 670 spectrophotometer with a Smart MIRacle horizontal attenuated total reflectance Ge crystal accessory), and by differential thermal analysis and thermogravimetric analysis (DTA/TGA, 2960 Simultaneous DTA±TGA by TA Instruments) operated at 10 C min ±1 from 30 to 1200 C with argon sweep gas.

A Highly Stable Anode, Carbon‐Free, Catalyst Support Based on Tungsten Trioxide Nanoclusters for Proton‐Exchange Membrane Fuel Cells

“…Furthermore, WO 3 can react with hydrogen to give H x WO 3 species, such as H 0.18 WO 3 , H 0.35 WO 3 , and substoichiometric oxides (WO 3Ày ). [27,28] Thus, WO 3 is capable of …”

Catalytic Hydrogen Production from Bioethanol

“…Various synthesis methods have been successfully demonstrated to get TiO 2 supported catalyst with desirable particle size and morphology for hydrogen generation maximization. Besides TiO 2 supported catalyst, there are multiple other novel semiconductors being developed recently for effective hydrogen production including CdS [15], VO 2 [16], WO 3 [17], and ZnSn(OH) 6 [18]. Nevertheless, the hydrogen production efficiency from catalytic ethanol oxidation still remains at very low level probably due to two facts: the fast recombination rate of the created electron-hole pairs and the low photon absorption efficiency at visible light range.…”

Colour tunable electrochromic devices based on PProDOT-(Hx)2 and PProDOT-(EtHx)2 polymers

“…Prior to device assembly, surface profilometry images of 20 PProDOT and PMAS films ( Figure S1 (a), (b)) illustrated that smooth and uniform films were obtained by spin coating. Film thicknesses of spun films were calculated from profile curves ( Figure S1 (c), (d)) and listed in Table 1.…”

“…In general, electrochromism can be defined as the process of 30 switching the UV-vis absorption profile of a material with application of an electric field or passing of electronic charge [17][18][19] . Over the years, a number of EC materials, including metal oxides 20,21 , such as WO 3, and conducting polymers, [22][23][24] such as polyethylenedioxythiphene (PEDOT), have been reported and 35 reviewed. These studies range from the synthesis of EC materials with high contrast [25][26][27] to scalable electrochromic device (ECD) fabrication 28,29 .…”

“…The influence of charge balance between PMAS and PProDOT on ECD performance was evaluated by assembling devices with different charge ratios ( Table 3). The charge capacity values were calculated from the 100 th cycle of the CV curves for balance 20 consideration. Three charge ratios, 0.97, 1.78, 0.67, were adopted for device performance characterization with the highest photopic contrast being obtained when the charge ratio was close to 1.…”