Two-dimensional (2D) materials catalysts provide an atomic-scale view on a fascinating arena for understanding the mechanism of electrocatalytic carbon dioxide reduction (CO2 ECR). Here, we successfully exfoliated both layered and nonlayered ultra-thin metal phosphorous trichalcogenides (MPCh3 ) nanosheets via wet grinding exfoliation (WGE), and systematically investigated the mechanism of MPCh3 as catalysts for CO2 ECR. Unlike the layered CoPS3 and NiPS3 nanosheets, the active Sn atoms tend to be exposed on the surfaces of nonlayered SnPS3 nanosheets. Correspondingly, the nonlayered SnPS3 nanosheets exhibit clearly improved catalytic activity, showing formic acid selectivity up to 31.6 % with -7.51 mA cm-2 at -0.65 V vs. RHE. The enhanced catalytic performance can be attributed to the formation of HCOO* via the first proton-electron pair addition on the SnPS3 surface. These results provide a new avenue to understand the novel CO2 ECR mechanism of Sn-based and MPCh3 -based catalysts.
- Klíčová slova
- 2D Materials, CO2 ECR, Exfoliation, MPCh3 Nanosheets, Nonlayered,
- Publikační typ
- časopisecké články MeSH
A metal-free organic sensitizer, suitable for the application in dye-sensitized solar cells (DSSCs), has been designed, synthesized and characterized both experimentally and theoretically. The structure of the novel donor-acceptor-π-bridge-acceptor (D-A-π-A) dye incorporates a triphenylamine (TPA) segment and 4-(benzo[c][1,2,5]thiadiazol-4-ylethynyl)benzoic acid (BTEBA). The triphenylamine unit is widely used as an electron donor for photosensitizers, owing to its nonplanar molecular configuration and excellent electron-donating capability, whereas 4-(benzo[c][1,2,5]thiadiazol-4-ylethynyl)benzoic acid is used as an electron acceptor unit. The influences of I3- /I- , [Co(bpy)3 ]3+/2+ and [Cu(tmby)2 ]2+/+ (tmby=4,4',6,6'-tetramethyl-2,2'-bipyridine) as redox electrolytes on the DSSC device performance were also investigated. The maximal monochromatic incident photon-to-current conversion efficiency (IPCE) reached 81 % and the solar light to electrical energy conversion efficiency of devices with [Cu(tmby)2 ]2+/+ reached 7.15 %. The devices with [Co(bpy)3 ]3+/2+ and I3- /I- electrolytes gave efficiencies of 5.22 % and 6.14 %, respectively. The lowest device performance with a [Co(bpy)3 ]3+/2+ -based electrolyte is attributed to increased charge recombination.
- Klíčová slova
- copper, donor-acceptor systems, dyes, electrolytes, solar cells,
- MeSH
- aniliny chemie MeSH
- barvicí látky chemie MeSH
- elektrochemické techniky přístrojové vybavení metody MeSH
- elektrolyty chemie MeSH
- elektrony MeSH
- kyselina benzoová chemie MeSH
- oxidace-redukce MeSH
- sluneční energie * MeSH
- spektrofotometrie ultrafialová MeSH
- teorie funkcionálu hustoty MeSH
- zdroje elektrické energie * MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- aniliny MeSH
- barvicí látky MeSH
- elektrolyty MeSH
- kyselina benzoová MeSH
Redox mediators play a major role determining the photocurrent and the photovoltage in dye-sensitized solar cells (DSCs). To maintain the photocurrent, the reduction of oxidized dye by the redox mediator should be significantly faster than the electron back transfer between TiO2 and the oxidized dye. The driving force for dye regeneration with the redox mediator should be sufficiently low to provide high photovoltages. With the introduction of our new copper complexes as promising redox mediators in DSCs both criteria are satisfied to enhance power conversion efficiencies. In this study, two copper bipyridyl complexes, Cu(II/I)(dmby)2TFSI2/1 (0.97 V vs SHE, dmby = 6,6'-dimethyl-2,2'-bipyridine) and Cu(II/I)(tmby)2TFSI2/1 (0.87 V vs SHE, tmby = 4,4',6,6'-tetramethyl-2,2'-bipyridine), are presented as new redox couples for DSCs. They are compared to previously reported Cu(II/I)(dmp)2TFSI2/1 (0.93 V vs SHE, dmp = bis(2,9-dimethyl-1,10-phenanthroline). Due to the small reorganization energy between Cu(I) and Cu(II) species, these copper complexes can sufficiently regenerate the oxidized dye molecules with close to unity yield at driving force potentials as low as 0.1 V. The high photovoltages of over 1.0 V were achieved by the series of copper complex based redox mediators without compromising photocurrent densities. Despite the small driving forces for dye regeneration, fast and efficient dye regeneration (2-3 μs) was observed for both complexes. As another advantage, the electron back transfer (recombination) rates were slower with Cu(II/I)(tmby)2TFSI2/1 as evidenced by longer lifetimes. The solar-to-electrical power conversion efficiencies for [Cu(tmby)2]2+/1+, [Cu(dmby)2]2+/1+, and [Cu(dmp)2]2+/1+ based electrolytes were 10.3%, 10.0%, and 10.3%, respectively, using the organic Y123 dye under 1000 W m-2 AM1.5G illumination. The high photovoltaic performance of Cu-based redox mediators underlines the significant potential of the new redox mediators and points to a new research and development direction for DSCs.
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Titania nanofibers were fabricated using the industrial Nanospider(TM) technology. The preparative protocol was optimized by screening various precursor materials to get pure anatase nanofibers. Composite films were prepared by mixing a commercial paste of nanocrystalline anatase particles with the electrospun nanofibers, which were shortened by milling. The composite films were sensitized by Ru-bipyridine dye (coded C106) and the solar conversion efficiency was tested in a dye-sensitized solar cell filled with iodide-based electrolyte solution (coded Z960). The solar conversion efficiency of a solar cell with the optimized composite electrode (η = 7.53% at AM 1.5 irradiation) outperforms that of a solar cell with pure nanoparticle film (η = 5.44%). Still larger improvement was found for lower light intensities. At 10% sun illumination, the best composite electrode showed η = 7.04%, referenced to that of pure nanoparticle film (η = 4.69%). There are non-monotonic relations between the film's surface area, dye sorption capacity and solar performance of nanofiber-containing composite films, but the beneficial effect of the nanofiber morphology for enhancement of the solar efficiency has been demonstrated.
- MeSH
- 2,2'-dipyridyl analogy a deriváty chemie MeSH
- barvicí látky chemie MeSH
- elektrody MeSH
- elektrolyty chemie MeSH
- nanočástice chemie MeSH
- nanovlákna chemie ultrastruktura MeSH
- organokovové sloučeniny chemie MeSH
- polymery chemie MeSH
- sluneční energie * MeSH
- titan chemie MeSH
- zdroje elektrické energie * MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- 2,2'-dipyridyl MeSH
- barvicí látky MeSH
- bis(bipyridyl)ruthenium(II) MeSH Prohlížeč
- elektrolyty MeSH
- organokovové sloučeniny MeSH
- polymery MeSH
- titan MeSH
- titanium dioxide MeSH Prohlížeč
Graphene nanoplatelets (GNP) in the form of thin semitransparent films on F-doped SnO2 (FTO) exhibit high electrocatalytic activity for the Co(bpy)3(3+/2+) redox couple in acetonitrile electrolyte solution. The GNP film is superior to the traditional electrocatalyst, that is, platinum, both in charge-transfer resistance (exchange current) and in electrochemical stability under prolonged potential cycling. The good electrochemical performance of GNP is readily applicable for dye-sensitized solar cells with Y123-sensitized TiO2 photoanodes and Co(bpy)3(3+/2+) as the redox shuttle. The dye-sensitized solar cell with GNP cathode is superior to that with the Pt-FTO cathode particularly in fill factor and in power conversion efficiency at higher illumination intensity.
- MeSH
- 2,2'-dipyridyl chemie MeSH
- barvicí látky chemie MeSH
- elektrochemie MeSH
- elektrody MeSH
- grafit chemie MeSH
- katalýza MeSH
- nanostruktury chemie MeSH
- oxidace-redukce MeSH
- sluneční energie MeSH
- zdroje elektrické energie * MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- 2,2'-dipyridyl MeSH
- barvicí látky MeSH
- grafit MeSH
Graphene nanoplatelets (GNP) in the form of thin semitransparent film on F-doped SnO(2) (FTO) exhibit high electrocatalytic activity for Co(L)(2); where L is 6-(1H-pyrazol-1-yl)-2,2'-bipyridine. The exchange current densities for the Co(2+/3+)(L)(2) redox reaction scaled linearly with the GNP film's optical absorbance, and they were by 1-2 orders of magnitude larger than those for the I(3)(-)/I(-) couple on the same electrode. The electrocatalytic activity of GNP films with optical transmission below 88% is outperforming the activity of platinized FTO for the Co(2+/3+)(L)(2) redox reaction. Dye-sensitized solar cells with Y123 dye adsorbed on TiO(2) photoanode achieved energy conversion efficiencies between 8 and 10% for both GNP and Pt-based cathodes. However, the cell with GNP cathode is superior to that with Pt-FTO cathode particularly in fill factors and in the efficiency at higher illumination intensities.
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Commercial graphene nanoplatelets in the form of optically transparent thin films on F-doped SnO(2) (FTO) exhibited high electrocatalytic activity toward I(3)(-)/I(-) redox couple, particularly in electrolyte based on ionic liquid (Z952). The charge-transfer resistance, R(CT), was smaller by a factor of 5-6 in ionic liquid, compared to values in traditional electrolyte based on methoxypropionitrile solution (Z946). Optical spectra and electrochemical impedance confirm that the film's absorbance scales linearly with R(CT)(-1). Electrocatalytic properties of graphene nanoplatelets for the I(3)(-)/I(-) redox reaction are proportional to the concentration of active sites (edge defects and oxidic groups), independent of the electrolyte medium. Dye-sensitized solar cell (DSC) was assembled with this material as a cathode. Semitransparent (>85%) film of graphene nanoplatelets presented no barrier to drain photocurrents at 1 Sun illumination and potentials between 0 and ca. 0.3 V, but an order of magnitude decrease of R(CT) is still needed to improve the behavior of DSC near the open circuit potential and, consequently, the fill factor. We predict that the graphene composite is a strong candidate for replacing both Pt and FTO in cathodes for DSC.
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The Pluronic P123 templated mesoporous TiO2 film was grown via layer-by-layer deposition and characterized by a novel methodology based on the adsorption of n-pentane. Multiple-layer depositions did not perturb the mesoporous structure significantly. Our TiO2 film was sensitized by a newly developed Ru-bipyridine dye (N945) and was applied as a photoanode in dye-sensitized solar cell. The 1-microm-thick mesoporous film, made by the superposition of three layers, showed enhanced solar conversion efficiency by about 50% compared to that of traditional films of the same thickness made from randomly oriented anatase nanocrystals.
- Publikační typ
- časopisecké články MeSH
