Surface and bulk carrier recombination dynamics of rutile type TiO2 powder as revealed by sub-ns time-resolved diffuse reflection spectroscopy

Miyasato, Ryo; Sato, Haruyuki; Yano, Toshihiro; Fujiwara, Masazumi; Hashimoto, Hideki

doi:10.1016/j.jphotochem.2017.10.054

Cited by 8 publications

(5 citation statements)

References 37 publications

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“…Steady-state absorption spectral measurements were performed using a JASCO V-670 UV-vis spectrophotometer. Sub-ns pump–probe spectroscopic measurements were performed using a combination of a Ti:Sapphire regenerative amplifier (Hurricane-X, Spectra Physics, 100 fs pulse duration at 800 nm) and a sub-ns pump–probe time-resolved absorption spectrophotometry system (EOS Vis-Nir, Ultrafast Systems) 30 , 43 . Excitation pulses at 650 nm (737 nm) for Chl-A solution (or film) and 704 nm (727 nm) for the Chl-D solution (or film) were prepared through the second harmonic generation of the output of an optical parametric amplifier (OPA-800 CF, Spectra Physics).…”

Section: Methodsmentioning

confidence: 99%

Hydroquinone redox mediator enhances the photovoltaic performances of chlorophyll-based bio-inspired solar cells

et al. 2021

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Chlorophyll (Chl) derivatives have recently been proposed as photoactive materials in next-generation bio-inspired solar cells, because of their natural abundance, environmental friendliness, excellent photoelectric performance, and biodegradability. However, the intrinsic excitation dynamics of Chl derivatives remain unclear. Here, we show sub-nanosecond pump–probe time-resolved absorption spectroscopy of Chl derivatives both in solution and solid film states. We observe the formation of triplet-excited states of Chl derivatives both in deoxygenated solutions and in film samples by adding all-trans-β-carotene as a triplet scavenger. In addition, radical species of the Chl derivatives in solution were identified by adding hydroquinone as a cation radical scavenger and/or anion radical donor. These radical species (either cations or anions) can become carriers in Chl-derivative-based solar cells. Remarkably, the introduction of hydroquinone to the film samples enhanced the carrier lifetimes and the power conversion efficiency of Chl-based solar cells by 20% (from pristine 1.29% to 1.55%). This enhancement is due to a charge recombination process of Chl-A+/Chl-D–, which is based on the natural Z-scheme process of photosynthesis.

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Section: Methodsmentioning

confidence: 99%

Hydroquinone redox mediator enhances the photovoltaic performances of chlorophyll-based bio-inspired solar cells

et al. 2021

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“…We would like to highlight that many TAS studies were performed in transmission mode, but many newly developed photocatalysts are opaque powders, for which diffuse reflectance characterisation is desirable. Diffuse-reflectance TAS has been applied to TiO 2 -based photocatalysts, [149][150][151][152][153] but so far there has been limited application of this technique to other photocatalytic systems, presumably due to (1) technical difficulties with obtaining good-quality data using diffuse reflectance TAS and (2) limited access to such specialised instrumentation. We highlight the importance of more widespread application of diffuse reflectance TAS to allow charge carrier dynamics in novel powder photocatalysts to be elucidated.…”

Section: Conclusion and Perspectivementioning

confidence: 99%

Charge carrier dynamics and reaction intermediates in heterogeneous photocatalysis by time-resolved spectroscopies

2022

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“…Meanwhile, as an intrinsic semiconductor, the bulk/surficial carrier recombination of TiO 2 greatly hinders its practical application. [24][25][26][27] In that case, some narrow bandgap semiconductors are also applied as the photoanode materials, such as Ta 3 N 5 (bandgap 2.1 eV), [28,29] BiVO 4 (bandgap 2.4 eV), and α-Fe 2 O 3 (bandgap 2.1 eV). [30][31][32] However, many of these narrow bandgap materials suffer from poor chemical stability and sluggish interfacial charge injection.…”

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Engineering Nanostructure–Interface of Photoanode Materials Toward Photoelectrochemical Water Oxidation

et al. 2021

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In practical applications, solar energy is usually converted to other forms of energy, such as electric energy, [9][10][11] chemical energy, [12,13] thermal energy, [14,15] so as to facilitate further transportation and storage. Among them, photoelectrochemical (PEC) reactions from water to hydrogen, CO 2 to C2+ products, and N 2 to NH 3 in the aqueous-based environment have been considered to be quite promising solar-chemical energy conversion pathways. [16][17][18][19] Unlike the traditional water electrolyzing system, the most ideal PEC reaction system can be selfdriven by illumination without external bias. Utilizing the electron-hole carriers generated from the semiconductor photoelectrode, redox reactions take place separately on the photocathode and photoanode. However, as the water oxidation reaction involves a complex four-proton coupled multi-electron process (2H 2 O + 4h + → O 2 + 4H + , E o = 1.23 V vs reversible hydrogen electrode (RHE)), it makes the water oxidation reaction the rate-control step in the watersplitting reaction. [20] Therefore, developing high-performance photo anodes is of great fundamental importance and interest.At the present stage, TiO 2 is the most studied and applied semiconductor photoelectrocatalyst, due to its outstanding chemical stability. [21][22][23] However, as a wide bandgap semiconductor (anatase TiO 2 : 3.2eV, rutile TiO 2 : 3.0 eV), TiO 2 can only respond to the ultraviolet light. Meanwhile, as an intrinsic semiconductor, the bulk/surficial carrier recombination of TiO 2 greatly hinders its practical application. [24][25][26][27] In that case, some narrow bandgap semiconductors are also applied as the photoanode materials, such as Ta 3 N 5 (bandgap 2.1 eV), [28,29] BiVO 4 (bandgap 2.4 eV), and α-Fe 2 O 3 (bandgap 2.1 eV). [30][31][32] However, many of these narrow bandgap materials suffer from poor chemical stability and sluggish interfacial charge injection. [33][34][35] As intrinsic semiconductor materials, both wide and narrow bandgap semiconductor photoanode materials are suffering from the poor bulk-phase carrier separation, intense surficial e − /h + trapping recombination, and sluggish electrode/electrolyte carrier injection kinetics. [36][37][38][39] Fortunately, with the continuous investment of researchers, a series of modification methods have been established and the PEC water oxidation performance of semiconductor photoanode materials has been significantly improved. [32,[40][41][42][43][44] Among various strategies, nanostructure-interface engineering is widely regarded as an effective method to improve the PEC water oxidation performance: [40,41] the light-harvesting performance can be enhanced by the widened optical Photoelectrochemical (PEC) water oxidation based on semiconductor materials plays an important role in the production of clean fuel and value-added chemicals. Nanostructure-interface engineering has proven to be an effective way to construct highly efficient PEC water oxidation photoanodes with good light capture, carrier transport, and ...

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Surface and bulk carrier recombination dynamics of rutile type TiO2 powder as revealed by sub-ns time-resolved diffuse reflection spectroscopy

Cited by 8 publications

References 37 publications

Hydroquinone redox mediator enhances the photovoltaic performances of chlorophyll-based bio-inspired solar cells

Hydroquinone redox mediator enhances the photovoltaic performances of chlorophyll-based bio-inspired solar cells

Charge carrier dynamics and reaction intermediates in heterogeneous photocatalysis by time-resolved spectroscopies

Engineering Nanostructure–Interface of Photoanode Materials Toward Photoelectrochemical Water Oxidation

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