Photocatalytically Active Ladder Polymers

Conjugated ladder polymers (cLaPs) are introduced as organic semiconductors for photocatalytic hydrogen evolution from water under sacrificial conditions. Starting from a linear conjugated polymer (cLiP1), two ladder polymers are synthesized via post-polymerization annulation and oxidation techniques to generate rigidified, planarized materials bearing dibenzo[b,d]thiophene (cLaP1) and dibenzo[b,d]thiophene sulfone subunits (cLaP2). The high photocatalytic activity of cLaP1 (1307 μmol h−1 g−1) in comparison to cLaP2 (18 μmol h−1 g−1) under broadband illumination (λ >295 nm) in presence of a hole-scavenger is attributed to a higher yield of long-lived charges (µs–ms timescale), as evidenced by transient absorption spectroscopy. Additionally, cLaP1 has a larger overpotential for proton reduction and thus an increased driving force for the evolution of hydrogen under sacrificial conditions.

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Photocatalyst Z-Scheme System Composed of a Linear Conjugated Polymer and BiVO4 for Overall Water Splitting Under Visible Light

10.26434/chemrxiv.12252317 ◽

2020 ◽

Author(s):

Yang Bai ◽

Keita Nakagawa ◽

Alexander Cowan ◽

Catherine Aitchison ◽

Yuichi Yamaguchi ◽

...

Keyword(s):

Visible Light ◽

Water Splitting ◽

Water Oxidation ◽

Conjugated Polymer ◽

High Throughput Screening ◽

Transient Absorption ◽

Transient Absorption Spectroscopy ◽

Proton Reduction ◽

Overall Water Splitting ◽

Multiple Components

Linear conjugated polymers have potential as photocatalysts for hydrogen production from water but so far, most studies have involved non-scalable sacrificial reagents. Z-schemes comprising more than one semiconductor are a potential solution, but it is challenging to design these systems because multiple components must work together synergistically. Here, we show that a conjugated polymer photocatalyst for proton reduction can be coupled in a Z-scheme with an inorganic water oxidation photocatalyst to promote overall water splitting without any sacrificial reagents. First, a promising combination of an organic catalyst, an inorganic catalyst, and a redox mediator was identified by using high-throughput screening of a library of components. A Z-scheme system composed of P10 (homopolymer of dibenzo[b,d]thiophene sulfone)-Fe2+/Fe3+-BiVO4 was then constructed for overall water splitting under visible light irradiation. Transient absorption spectroscopy was used to assign timescales to the various steps in the photocatalytic process. While the overall solar-to-hydrogen efficiency of this first example is low, it provides proof of concept for other hybrid organic-inorganic Z-scheme architectures in the future.

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Photocatalyst Z-Scheme System Composed of a Linear Conjugated Polymer and BiVO4 for Overall Water Splitting Under Visible Light

10.26434/chemrxiv.12252317.v1 ◽

2020 ◽

Author(s):

Yang Bai ◽

Keita Nakagawa ◽

Alexander Cowan ◽

Catherine Aitchison ◽

Yuichi Yamaguchi ◽

...

Keyword(s):

Visible Light ◽

Water Splitting ◽

Water Oxidation ◽

Conjugated Polymer ◽

High Throughput Screening ◽

Transient Absorption ◽

Transient Absorption Spectroscopy ◽

Proton Reduction ◽

Overall Water Splitting ◽

Multiple Components

Linear conjugated polymers have potential as photocatalysts for hydrogen production from water but so far, most studies have involved non-scalable sacrificial reagents. Z-schemes comprising more than one semiconductor are a potential solution, but it is challenging to design these systems because multiple components must work together synergistically. Here, we show that a conjugated polymer photocatalyst for proton reduction can be coupled in a Z-scheme with an inorganic water oxidation photocatalyst to promote overall water splitting without any sacrificial reagents. First, a promising combination of an organic catalyst, an inorganic catalyst, and a redox mediator was identified by using high-throughput screening of a library of components. A Z-scheme system composed of P10 (homopolymer of dibenzo[b,d]thiophene sulfone)-Fe2+/Fe3+-BiVO4 was then constructed for overall water splitting under visible light irradiation. Transient absorption spectroscopy was used to assign timescales to the various steps in the photocatalytic process. While the overall solar-to-hydrogen efficiency of this first example is low, it provides proof of concept for other hybrid organic-inorganic Z-scheme architectures in the future.

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Reactivity and Mechanism of Photo- and Electrocatalytic Hydrogen Evolution by a Diimine Copper(I) Complex

Catalysts ◽

10.3390/catal10111302 ◽

2020 ◽

Vol 10 (11) ◽

pp. 1302

Author(s):

Maria Drosou ◽

Fotios Kamatsos ◽

George Ioannidis ◽

Athanasios Zarkadoulas ◽

Christiana A. Mitsopoulou ◽

...

Keyword(s):

Photocatalytic Activity ◽

Dft Calculations ◽

Hydrogen Evolution ◽

Molecular Mechanisms ◽

High Photocatalytic Activity ◽

Proton Exchange ◽

H2 Evolution ◽

Turnover Number ◽

Proton Reduction ◽

Insight Into

The tetrahedral copper(I) diimine complex [Cu(pq)2]BF4 displays high photocatalytic activity for the H2 evolution reaction with a turnover number of 3564, thus representing the first type of a Cu(I) quinoxaline complex capable of catalyzing proton reduction. Electrochemical experiments indicate that molecular mechanisms prevail and DFT calculations provide in-depth insight into the catalytic pathway, suggesting that the coordinating nitrogens play crucial roles in proton exchange and hydrogen formation.

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Dye-sensitized Pt@TiO2 core–shell nanostructures for the efficient photocatalytic generation of hydrogen

Beilstein Journal of Nanotechnology ◽

10.3762/bjnano.5.41 ◽

2014 ◽

Vol 5 ◽

pp. 360-364 ◽

Cited By ~ 13

Author(s):

Jun Fang ◽

Lisha Yin ◽

Shaowen Cao ◽

Yusen Liao ◽

Can Xue

Keyword(s):

Photocatalytic Activity ◽

High Photocatalytic Activity ◽

Shell Structures ◽

Core Shell ◽

Synergic Effect ◽

Proton Reduction ◽

Dye Sensitization ◽

Dye Sensitized ◽

Shell Nanostructures ◽

Photogenerated Electrons

Pt@TiO2 core–shell nanostructures were prepared through a hydrothermal method. The dye-sensitization of these Pt@TiO2 core–shell structures allows for a high photocatalytic activity for the generation of hydrogen from proton reduction under visible-light irradiation. When the dyes and TiO2 were co-excited through the combination of two irradiation beams with different wavelengths, a synergic effect was observed, which led to a greatly enhanced H2 generation yield. This is attributed to the rational spatial distribution of the three components (dye, TiO2, Pt), and the vectored transport of photogenerated electrons from the dye to the Pt particles via the TiO2 particle bridge.

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Charge Accumulation Kinetics in Multi-redox Molecular Catalysts Immobilised on TiO2

10.26434/chemrxiv.12777359 ◽

2020 ◽

Author(s):

Carlota Bozal-Ginesta ◽

Camilo A. Mesa ◽

Annika Eisenschmidt ◽

Ravi Shankar ◽

Laia Francàs ◽

...

Keyword(s):

Electron Transfer ◽

Transient Absorption ◽

Transient Absorption Spectroscopy ◽

Redox Potentials ◽

Charge Accumulation ◽

Excitation Light ◽

Molecular Catalyst ◽

Hole Scavenger ◽

Accumulation Kinetics ◽

Molecular Catalysts

Multi-redox catalysis requires the transfer of more than one charge carrier and is crucial for solar energy conversion into fuels and valuable chemicals. In photo(electro)chemical systems, however, the necessary accumulation of multiple, long-lived charges is challenged by recombination with their counterparts. Herein, we investigate charge accumulation in two model multi-redox molecular catalysts for proton and CO2 reduction attached onto mesoporous TiO2 electrodes. Transient absorption spectroscopy and spectroelectrochemical techniques have been employed to study the kinetics of photoinduced electron transfer from the TiO2 to the molecular catalysts in acetonitrile, with triethanolamine as the hole scavenger. At high light intensities, we detect charge accumulation in the millisecond timescale in the form of multi-reduced species. The redox potentials of the catalysts and the capacity of TiO2 to accumulate electrons play an essential role in the charge accumulation process at the molecular catalyst. Recombination of reduced species with valence band holes in TiO2 is observed to be faster than microseconds, while electron transfer from multi-reduced species to the conduction band or the electrolyte occurs in the millisecond timescale. Finally, under light irradiation, we show how charge accumulation on the catalyst is regulated as a function of the applied bias and the excitation light intensity.

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Covalent organic frameworks with high quantum efficiency in photocatalytic hydrogen evolution: mediating charge separation

10.21203/rs.3.rs-1020038/v1 ◽

2021 ◽

Author(s):

Chunzhi Li ◽

Jiali Liu ◽

He Li ◽

Kaifeng Wu ◽

Junhui Wang ◽

...

Keyword(s):

Charge Carrier ◽

Quantum Efficiency ◽

Organic Semiconductors ◽

Transient Absorption ◽

Active Species ◽

Binding Energies ◽

Transient Absorption Spectroscopy ◽

High Quantum Efficiency ◽

Inorganic Semiconductors ◽

Femtosecond Transient Absorption

Abstract Compared with inorganic semiconductors, the difficulty of exciton dissociation is one of the main reasons for the lower photocatalytic activity of organic semiconductors. In this work, we report that the charge carrier lifetime is dramatically prolonged by incorporating a suitable donor-acceptor (β-ketene-CN) pair to a covalent organic framework nanosheet (CN-CON). CN-CON showed remarkably high apparent quantum efficiency up to 82.6% at 450 nm in photocatalytic H2 evolution, superior to all the COFs reported so far. The charge carrier kinetic analysis and femtosecond transient absorption spectroscopy characterizations verified that CN-CON had intrinsically lower exciton binding energies and hence longer-lived charge carriers than the corresponding CON without CN unit. This work provides an excellent model for gaining insight into the nature of ultrashort-lived active species in polymeric organic photocatalysts.

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