An official website of the United States government
Three copper redox shuttles ([Cu( 1 )] 2+/1+ , [Cu( 2 )] 2+/1+ , and [Cu( 3 )] 2+/1+ ) featuring tetradentate ligands were synthesized and evaluated computationally, electrochemically, and in dye-sensitized solar cell (DSC) devices using a benchmark organic dye, Y123 . Neutral polyaromatic ligands with limited flexibility were targeted as a strategy to improve solar-to-electrical energy conversion by reducing voltage losses associated with redox shuttle electron transfer events. Inner-sphere electron transfer reorganization energies ( λ ) were computed quantum chemically and compared to the commonly used [Co(bpy) 3 ] 3+/2+ redox shuttle which has a reported λ value of 0.61 eV. The geometrically constrained biphenyl-based Cu redox shuttles investigated here have lower reorganization energies (0.34–0.53 eV) and thus can potentially operate with lower driving forces for dye regeneration (Δ G reg ) in DSC devices when compared to [Co(bpy) 3 ] 3+/2+ -based devices. The rigid tetradentate ligand design promotes more efficient electron transfer reactions leading to an improved J SC (14.1 mA cm −2 ), higher stability due to the chelate effect, and a decrease in V lossOC for one of the copper redox shuttle-based devices.
more »
« less
Iron Redox Shuttles with Wide Optical Gap Dyes for High‐Voltage Dye‐Sensitized Solar Cells
Abstract A series of iron polypyridyl redox shuttles were synthesized in the 2+ and 3+ oxidation states and paired with a series of wide optical gap organic dyes with weak aryl ether electron‐donating groups. High voltage dye‐sensitized solar cell (HV‐DSC) devices were obtained through controlling the redox shuttle energetics and dye donor structure. The use of aryl ether donor groups, in place of commonly used aryl amines, allowed for the lowering of the dye ground‐state oxidation potential which enabled challenging to oxidize redox shuttles based on Fe2+polypyridyl structures to be used in functional devices. By carefully designing a dye series that varies the number of alkyl chains for TiO2surface protection, the recombination of electrons in TiO2to the oxidized redox shuttle could be controlled, leading to HV‐DSC devices of up to 1.4 V.
more »
« less
- Award ID(s):
- 1757220
- PAR ID:
- 10286463
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- ChemSusChem
- Volume:
- 14
- Issue:
- 15
- ISSN:
- 1864-5631
- Format(s):
- Medium: X Size: p. 3084-3096
- Size(s):
- p. 3084-3096
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Chemical redox reactions between redox shuttles and lithium-ion battery particles have applications in electrochemical systems including redox-mediated flow batteries, photo-assisted lithium-ion batteries, and lithium-ion battery overcharge protection. These previous studies, combined with interest in chemical redox of battery materials in general, has resulted in previous reports of the chemical oxidation and/or reduction of solid lithium-ion materials. However, in many of these reports, a single redox shuttle is the focus and/or the experimental conditions are relatively limited. Herein, a study of chemical redox for a series of redox shuttles reacted with a lithium-ion battery cathode material will be reported. Both oxidation and reduction of the solid material with redox shuttles as a function of time will be probed using ferrocene derivatives with different half-wave potentials. The progression of the chemical redox was tracked by using electrochemical analysis of the redox shuttles in a custom electrochemical cell, and rate constants for chemical redox were extracted from using two different models. This study provides evidence that redox shuttle-particle interactions play a role in the overall reaction rate, and more broadly support that this experimental method dependent on electrochemical analysis can be applied for comparison of redox shuttles reacting with solid electroactive materials.more » « less
-
Iodine binding to thiophene rings in dyes for dye-sensitized solar cells (DSCs) has been hypothesized to be performance degrading in a number of literature cases. Binding of iodine to dyes near the semiconductor surface can promote undesirable electron transfers and lower the overall efficiency of devices. Six thiophene or furan containing dye analogs were synthesized to analyze iodine binding to the dyes via Raman spectroscopy, UV-Vis studies, device performance metrics and density functional theory (DFT) based computations. Evidence suggests I 2 binds thiophene-based dyes stronger than furan-based dyes. This leads to higher DSC device currents and voltages from furan analogues, and longer electron lifetimes in DSC devices using furan based dyes. Raman spectrum of the TiO 2 surface-bound dyes reveals additional and more instense peaks for thiophene dyes in the presence of I 2 relative to no I 2 . Additionally, broader and shifted UV-Vis peaks are observed for thiophene dyes in the presence of I 2 on TiO 2 films suggesting significant interaction between the dye molecules and I 2 . These observations are also supported by DFT and TD-DFT calculations which indicate the absence of a key geometric energy minimum in the dye–I 2 ground state for furan dyes which are readily observed for the thiophene based analogues.more » « less
-
The high bond dissociation energy of C–C σ-bonds presents a challenge to chemical conversions in organic synthesis, polymer degradation, and biomass conversion that require chemoselective C–C bond cleavage at room temperature. Dye-sensitized photoelectrochemical cells (DSPECs) incorporating molecular organic dyes could offer a means of using renewable solar energy to drive these types of energetically demanding chemoselective C–C bond cleavage reactions. This study reports the solar light-driven activation of a bicyclic aminoxyl mediator to achieve C–C bond cleavage in the aryl-ether linkage of a lignin model compound (LMC) at room temperature using a donor–π-conjugated bridge–acceptor (D–π–A) organic dye-based DSPEC system. Mesoporous TiO 2 photoanode surfaces modified with 5-[4-(diphenylamino)phenyl]thiophene-2-cyanoacrylic acid (DPTC) D–π–A organic dye were investigated along with a bicyclic aminoxyl radical mediator (9-azabicyclo[3,3,1]nonan-3-one-9-oxyl, KABNO) in solution with and without the presence of LMC. Photophysical studies of DPTC with KABNO showed intermolecular energy/electron transfer under 1 sun illumination (100 mW cm −2 ). Under illumination, the D–π–A type DPTC sensitized TiO 2 photoanodes facilitate the generation of the reactive oxoammonium species KABNO+ as a strong oxidizing agent, which is required to drive the oxidative C–C bond cleavage of LMC. The photoelectrochemical oxidative reaction in a complete DSPEC with KABNO afforded C–C bond cleavage products 2-(2-methoxyphenoxy)acrylaldehyde (94%) and 2,6-dimethoxy-1,4-benzoquinone (66%). This process provides a first report utilizing a D–π–A type organic dye in combination with a bicyclic nitroxyl radical mediator for heterogeneous photoelectrolytic oxidative cleavage of C–C σ-bonds, modeled on those found in lignin, at room temperature.more » « less
-
Abstract When a few drops of acid (hydrochloric, acrylic, propionic, acetic, or formic) are added to a colloid comprised of 1D lepidocrocite titanate nanofilaments (1DLs)–2 × 2 TiO6octahedra in cross‐section–a hydrogel forms, in many cases, within seconds. The 1DL synthesis process requires the reaction between titanium diboride with tetramethylammonium (TMA+), hydroxide. Using quantitative nuclear magnetic resonance (qNMR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC), the mass percent of TMA+after synthesis is determined to be ≈ 13.1 ± 0.1%. The TMA+is completely removed from the gels after 2 water soak cycles, resulting in the first completely inorganic, TiO2‐based hydrogels. Ion exchanging the TMA+with hydronium results in gels with relatively strong hydrogen bonds. The hydrogels' compression strengths increased linearly with 1DL colloid concentration. At a 1DL concentration of 45 g L−1, the compressive strength, at 80% deformation when acrylic acid is used, is ≈325 kPa. The strengths are ≈ 50% greater after the TMA+is removed. The removal of all residual organic components in the hydrogels, including TMA+, is confirmed by qNMR, Fourier‐transformed infrared spectroscopy (FTIR), and TGA/DSC. The 1DL phase is retained after gelation, TMA+removal, and 80% compression.more » « less
