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Herein we report on the adsorption and photocatalytic decomposition of organic molecules in aqueous environments containing two-dimensional Ti 3 C 2 T x , a representative of the MXene family.
Two sensitizers, [Ru(bpy) 2 (dcb)] 2+ ( RuC ) and [Ru(bpy) 2 (dpb)] 2+ ( RuP ), were anchored to mesoporous TiO 2 thin films and utilized to sensitize the reaction of TiO 2 electrons with oxidized triphenylamines to visible light in CH 3 CN electrolytes.
New branched alkyl tetrathienothiophene (TTAR)-based organic sensitizers with power conversion efficiency up to 11%.
A reversible ligand exchange of the Cu( ii ) redox shuttle is shown to reduce recombination, leading to excellent performance in DSSCs.
Using IR absorption anisotropy, interligand energy transfer in N712 is shown to occur on a sub-ps time scale, and is thus unlikely to limit injection in DSSCs.
We report the results of measurements of the threshold of Freedericksz transition in a nematic liquid crystal doped by Methyl-red. We show that in case of dc field the threshold voltage can decrease or increase depending on the light dose, due to the light-induced desorption and adsorption of charge complexes from and on the irradiated surface, that has been recently demonstrated. This effect has the potential to be exploited in optical devices such as liquid crystal microlenses and spatial light modulators.
The isolation of crystallite anatase from commercial TiO{sub 2} P25 Degussa was investigated. The aim of this research was to study of isolated anatase based DSSC as an effort to develop industrial DSSC. The crystal phase, crystallite size and crystal shape both of original P25 and isolated anatase were characterized by XRD and TEM. By observing DSSC parameters such as FF, Jsc and Voc resulted in cell test, the efficiency of samples based DSSC was known. The isolation of anatase crystal was done by dissolving P25 in ammonia catalyzed hydrogen peroxide solution for 15 hours followed by washing and drying. DSSC cell performance was evaluated by applying the isolated anantase and original P25 as photoanode in the Gratzel cell system. The observation of cell efficiency was measured under 100 mW /cm{sup 2} with active area 1.5 cm{sup 2}. X-ray diffraction pattern showed obviously that no rutile contaminant in produced isolated anatase. TEM image shows typical anatase crystal with the particle size 21 nm. Surface area measurement exhibits that surface area of isolated anatase was 64.7m{sup 2}/g. I-V measurement showed that the efficiency of anatase based cell and P25 based cell is 0.79% and 0.51% respectively.
Simple chemical deposition method for the synthesis of ZnO/CdS bilayer photoelectrode on fluorine doped tin oxide (FTO) coated glass substrate in aqueous medium at low temperature (< 373K) is described. The different preparative parameters such as deposition time, bath temperature, concentration of precursor solution and, pH of the bath etc. were optimized. Nanograined ZnO was deposited on FTO coated glass substrates by dip-coating method, whereas CdS nanorods were successfully synthesized on pre-deposited ZnO film by Chemical Bath Deposition (CBD) method. The Photovoltaic properties of FTO/ZnO/CdS bilayer photo electrodes were also studied. A maximum short circuit current density of 9.1 mA cm-2 and conversion efficiency 1.05% are observed for ZnO/CdS-10min. Layer, which supports fast electron injection kinetics due to hetero structured nanorod, while minimum values of 0.53mA cm-2 and 0.01% respectively are observed for only ZnO deposited layer.
This paper demonstrates the facile synthesis of high performance silver-polypyrrole-multiwall carbon nanotubes (Ag-PPy-FMWCNTS) nanocomposites via electrodeposition method on stainless steel substrate and its application as a low cost counter electrode (CE) for the precious platinum (Pt) free DSSC. The nanocomposites were characterized by variety of techniques such as Fourier transforms infrared (FTIR), X-ray diffraction, Scanning electron microscope (SEM), cyclic voltammetry (CV) and Four probe technique respectively. The cyclic voltammetry and Tafel polymerization measurements of Ag-PPy-FMWCNTS nanocomposites CE reveal the favorable electrocatalytic activity and low charge transfer resistance R{sub ct}(2.50 Ω cm{sup 2}) for I{sub 3}{sup −}/I{sup −} redox solution. The four probe studies showed the large electrical conductivity (226S cm{sup −1}) of Ag-PPy-FMWCNTS nanocomposite. The DSSC assembled with Ag-PPy-FMWCNTS nanocomposites CE display the considerable short circuit current density (13.95 mA cm{sup −2}) and acceptable solar to electrical conversion efficiency of 7.6%, which is higher to the efficiency of DSSC with thermally decomposed Pt reference electrode 7.1%. The excellent conversion efficiency, rapid charge transfer in combination with low cost and simple fabrication method of Ag-PPy-FMWCNTS nanocomposites can be exploited as an efficient and potential candidate to replace the Pt CE for large scale production of DSSC.
A mesoporous atomic layer deposition (ALD) double-shell electrode, Al 2 O 3 (insulating core)//ALD ZnO|ALD TiO 2 , on a fluorine-doped tin oxide (FTO) conducting substrate was explored for a photoanode assembly, FTO//Al 2 O 3 (insulating core)//ALD ZnO|ALD TiO 2 |–chromophore–catalyst, for light-driven water oxidation. Photocurrent densities at photoanodes based on mesoporous ALD double-shell (ALD ZnO|ALD TiO 2 |) and ALD single-shell (ALD ZnO|, ALD TiO 2 |) electrodes were investigated for O 2 evaluation by a generator–collector dual working electrode configuration. The high photocurrent densities obtained based on the mesoporous ALD ZnO|ALD TiO 2 photoanode for O 2 evolution arise from a significant barrier to back electron transfer (BET) by the optimized tunneling barrier in the structure with the built-in electric field at the ALD ZnO|ALD TiO 2 interface. The charge recombination is thus largely decreased. Finally, in the films, BET following injection has been investigated through kinetic nanosecond transient absorption spectra, and the results of energy band analysis are used to derive insight into the internal electronic structure of the electrodes.
We describe here the preparation of a family of photoanodes for water oxidation that incorporate an electron acceptor–chromophore–catalyst in single molecular assemblies on nano-indium tin oxide (nanoITO) electrodes on fluorine-doped tin oxide (FTO). The assemblies were prepared by using a layer-by-layer, Atomic Layer Deposition (ALD), self-assembly approach. In the procedure, addition of an electron acceptor viologen derivative followed by a Ru II (bpy) chromophore and a pyridyl derivative of the water oxidation catalyst [Ru(bda) (L) 2 ] (bda = 2,2'-bipyridine-6,6'-dicarboxylate) 2 , were linked by ALD by addition of the bridge precursors TiO 2 , ZrO 2 , and Al 2 O 3 as the bridging groups giving the assemblies, FTO|nanoITO|–MV 2+ –ALD MO 2 –RuP2 2+ –ALD M'O 2 –WOC. In a series of devices, the most efficient gave water oxidation with an incident photon to current efficiency of 2.2% at 440 nm. Transient nanosecond absorption measurements on the assemblies demonstrated that the slow step in the intra-assembly electron transfer is the electron transfer from the chromophore through the viologen bridge to the nanoITO electrode.
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Significance The capture and conversion of sunlight into a useful chemical fuel (H 2 , CH 4 , CH 3 OH, etc.) is a central goal of the field of artificial photosynthesis. Water oxidation to generate O 2 and protons stands as the major bottleneck in these processes. Relatively few stable photosensitizers can generate sufficient oxidizing power to drive water oxidation, and those that do contain rare elements such as ruthenium. In this paper, we show that metal-free organic photosensitizers are capable of driving photoelectrochemical water oxidation. Significantly, these photosensitizers exhibit comparable activity to that of ruthenium-containing photosensitizers under broadband illumination. In addition, we report to our knowledge the first demonstration of a molecular photosensitizer, outside of natural photosynthesis, that can drive water oxidation utilizing only red light.
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In the development of photoelectrochemical cells for water splitting or CO 2 reduction, a major challenge is O 2 evolution at photoelectrodes that, in behavior, mimic photosystem II. At an appropriate semiconductor electrode, a water oxidation catalyst must be integrated with a visible light absorber in a stable half-cell configuration. Here, we describe an electrode consisting of a light absorber, an intermediate electron donor layer, and a water oxidation catalyst for sustained light driven water oxidation catalysis. In assembling the electrode on nanoparticle SnO 2 /TiO 2 electrodes, a Ru(II) polypyridyl complex was used as the light absorber, NiO was deposited as an overlayer, and a Ru(II) 2,2′-bipyridine-6,6′-dicarboxylate complex as the water oxidation catalyst. In the final electrode, addition of the NiO overlayer enhanced performance toward water oxidation with the final electrode operating with a 1.1 mA/cm 2 photocurrent density for 2 h without decomposition under one sun illumination in a pH 4.65 solution. We attribute the enhanced performance to the role of NiO as an electron transfer mediator between the light absorber and the catalyst.
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