Metal-free organic sensitizers for use in water-splitting dye-sensitized photoelectrochemical cells

Swierk, John R.; Méndez-Hernández, Dalvin D.; McCool, Nicholas S.; Liddell, Paul A.; Terazono, Yuichi; Pahk, Ian; Tomlin, John; Oster, Nolan V.; Moore, Thomas A.; Moore, Ana L.; Gust, Devens; Mallouk, Thomas E.

doi:10.1073/pnas.1414901112

Cited by 138 publications

(116 citation statements)

References 42 publications

(58 reference statements)

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“…This is good agreement with our previous measurements of the internal quantum yields of WS-DSPECs. 8,13 Where then are the missing electrons? Though some of these electrons may be lost to rapid scavenging by the IrO 2 nanoparticles spread throughout the electrode, 16 the concentration of IrO 2 is too low for this to account for the majority of the missing electrons.…”

Section: T Scav Irmentioning

confidence: 99%

Dynamics of Electron Recombination and Transport in Water-Splitting Dye-Sensitized Photoanodes

2015

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Water-splitting dye-sensitized photoelectrochemical cells (WS-DSPECs) use visible light to split water using molecular sensitizers and water oxidation catalysts codeposited onto mesoporous TiO 2 electrodes. Despite a high quantum yield of charge injection and low requirement for the catalytic turnover rate, the quantum yield of water splitting in WS-DSPECs is typically low (<1%). Here we examine the charge separation and recombination processes in WS-DSPECs photoanodes functionalized with varying amounts of IrO 2 nanoparticle catalyst. Charge extraction and transient open-circuit voltage decay measurements provide insight into the relationship between light intensity, conduction band electron density, open-circuit photovoltage, and recombination time scale. We correlate these results with electrochemical impedance spectroscopy and present the first complete equivalent circuit model for a WS-DSPEC. The data show quantitatively that recombination of photoinjected electrons with oxidized sensitizer molecules and scavenging by the water oxidation catalyst limit the concentration of conduction band electrons and by extension the photocurrent of WS-DSPECs.

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Section: T Scav Irmentioning

confidence: 99%

Dynamics of Electron Recombination and Transport in Water-Splitting Dye-Sensitized Photoanodes

2015

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“…In these photo-electrochemical systems, intermolecular charge transfer between surface sensitizers can be used to funnel charges to catalysts to, for example, drive multi-electron reactions. 15,37,38 …”

Section: Hole Diffusion As a Probe Of The Surrounding Environment: Htmentioning

confidence: 99%

The Role of Hole Transport between Dyes in Solid-State Dye-Sensitized Solar Cells

Moia¹,

Cappel²,

Leijtens

et al. 2015

J. Phys. Chem. C

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In dye-sensitized solar cells (DSSCs) photo-generated positive charges are normally considered to be carried away from the dyes by a separate phase of hole transporting material (HTM). We show that there can also be significant transport within the dye monolayer itself before the hole reaches the HTM. We quantify the fraction of dye regeneration in solid state DSSCs that can be attributed to this process. By using cyclic voltammetry and transient anisotropy spectroscopy we demonstrate that the rate of inter-dye hole transport is prevented both on micrometer and nanometer length scales by reducing the dye loading on the TiO2 surface. The dye regeneration yield is quantified for films with high and low dye loadings (with and without hole percolation in the dye monolayer) infiltrated with varying levels of HTM. Inter-dye hole transport can account for >50% of the overall dye regeneration with low HTM pore filling. This is reduced to about 5% when the infiltration of the HTM in the pores is optimized in 2μm thick films. Finally, we use hole transport in the dye monolayer to characterize the spatial distribution of the HTM phase in the pores of the dyed mesoporous TiO2.

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“…4 Since then, numerous photocatalysts have been investigated for PEC water splitting, 5,6 such as TiO 2 , 7,8 α-Fe 2 O 3 , 9 C 3 N 4 , 10,11 Ta 3 N 5 12 and porphyrins. 13,14 Due to the achievement of photocatalysts, oxygen or hydrogen evolution process on the electrode surface has been no longer considered as crucial performance-limiting factors for PEC water splitting system. 15, 16 However, the fast charge recombination and slow charge separation [17][18][19][20][21][22] as well as poor surface catalytic activity are still existing as challenges for highly efficient PEC water splitting.…”

Section: Introductionmentioning

confidence: 99%

Photoelectrochemical Water Splitting System—A Study of Interfacial Charge Transfer with Scanning Electrochemical Microscopy

Zhang

Xiao

et al. 2016

ACS Appl. Mater. Interfaces

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Fast charge transfer kinetics at the photoelectrode/electrolyte interface is critical for efficient photoelectrochemical (PEC) water splitting system. Thus, far, a measurement of kinetics constants for such processes is limited. In this study, scanning electrochemical microscopy (SECM) is employed to investigate the charge transfer kinetics at the photoelectrode/electrolyte interface in the feedback mode in order to simulate the oxygen evolution process in PEC system. The popular photocatalysts BiVO4 and Mo doped BiVO4 (labeled as Mo:BiVO4) are selected as photoanodes and the common redox couple [Fe(CN)6](3-)/[Fe(CN)6](4-) as molecular probe. SECM characterization can directly reveal the surface catalytic reaction kinetics constant of 9.30 × 10(7) mol(-1) cm(3) s(-1) for the BiVO4. Furthermore, we find that after excitation, the ratio of rate constant for photogenerated hole to electron via Mo:BiVO4 reacting with mediator at the electrode/electrolyte interface is about 30 times larger than that of BiVO4. This suggests that introduction of Mo(6+) ion into BiVO4 can possibly facilitate solar to oxygen evolution (hole involved process) and suppress the interfacial back reaction (electron involved process) at photoanode/electrolyte interface. Therefore, the SECM measurement allows us to make a comprehensive analysis of interfacial charge transfer kinetics in PEC system.

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Metal-free organic sensitizers for use in water-splitting dye-sensitized photoelectrochemical cells

Cited by 138 publications

References 42 publications

Dynamics of Electron Recombination and Transport in Water-Splitting Dye-Sensitized Photoanodes

Dynamics of Electron Recombination and Transport in Water-Splitting Dye-Sensitized Photoanodes

The Role of Hole Transport between Dyes in Solid-State Dye-Sensitized Solar Cells

Photoelectrochemical Water Splitting System—A Study of Interfacial Charge Transfer with Scanning Electrochemical Microscopy

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