Conjugated polymers for visible-light-driven photocatalysis

Dai, Chunhui; Liu, Bin

doi:10.1039/c9ee01935a

Cited by 475 publications

(329 citation statements)

References 223 publications

(270 reference statements)

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“…[8,[258][259][260][261][262][263][264] However, the maximum EQEs of photo catalysts fabricated from the bulk semiconductors remained mostly below 1%, primarily due to inefficient charge separation within the bulk semiconductors. [265,266] As discussed previously, organic semiconductors have high exciton binding energies and typically require a heterojunction to split charges. Therefore, in photocatalysts comprising of a single organic semiconductor, only the excitons generated within the exciton diffusion length from the semiconductor/electrolyte, semiconductor/gas, or semiconductor/ cocatalyst heterojunctions at the semiconductor surface can Figure 9.…”

Section: Bulk Heterojunctions In Photocatalytic Applicationsmentioning

confidence: 98%

The Bulk Heterojunction in Organic Photovoltaic, Photodetector, and Photocatalytic Applications

et al. 2020

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Organic semiconductors require an energetic offset in order to photogenerate free charge carriers efficiently, owing to their inability to effectively screen charges. This is vitally important in order to achieve high power conversion efficiencies in organic solar cells. Early heterojunction‐based solar cells were limited to relatively modest efficiencies (<4%) owing to limitations such as poor exciton dissociation, limited photon harvesting, and high recombination losses. The development of the bulk heterojunction (BHJ) has significantly overcome these issues, resulting in dramatic improvements in organic photovoltaic performance, now exceeding 18% power conversion efficiencies. Here, the design and engineering strategies used to develop the optimal bulk heterojunction for solar‐cell, photodetector, and photocatalytic applications are discussed. Additionally, the thermodynamic driving forces in the creation and stability of the bulk heterojunction are presented, along with underlying photophysics in these blends. Finally, new opportunities to apply the knowledge accrued from BHJ solar cells to generate free charges for use in promising new applications are discussed.

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Section: Bulk Heterojunctions In Photocatalytic Applicationsmentioning

confidence: 98%

The Bulk Heterojunction in Organic Photovoltaic, Photodetector, and Photocatalytic Applications

et al. 2020

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“…In photocatalytic devices, the photogenerated charge carriers drive oxidation and reduction reactions at the electrolyte/polymer interface (i.e., proton reduction and water oxidation half reactions), which split water to generate fuels like H 2 , O 2, or H 2 O 2 . Typically, the organic photocatalyst is responsible to carry one of these reactions (mostly with the aid of a metal cocatalyst that can lower the overpotential or activation energy for the reaction), [155] while a second species (sacrificial agents) may be required to carry the other half reaction. The use of CPs as catalysts at the electrolyte interface has mostly involved H 2 evolution.…”

Section: Fuel Generation From An Aqueous Medium Via Photo or Electrocmentioning

confidence: 99%

“…In the case of O 2 evolution, nitrogen-rich CPs, based on covalent triazine frameworks, are the most represented class of organic materials. [155] However, examples of CPs used for overall water splitting remain scarce, limited mainly to carbon nitride materials. [156,157] This is due to the nature of the OER, where water is oxidized to O 2 via a four-electron process, a reaction difficult to catalyze due to slow kinetics and high overpotentials.…”

Section: Fuel Generation From An Aqueous Medium Via Photo or Electrocmentioning

confidence: 99%

“…For H 2 evolution by polymer photocatalysts, the lowest unoccupied molecular orbital (LUMO) of the polymer must be more negative than the reduction potential of the H + / H 2 redox couple situated at 0 V versus the normal hydrogen electrode (NHE), pH = 0 (−4.4 eV), while the highest occupied molecular orbital (HOMO) must be more positive than the oxidation potential of the O 2 /H 2 O redox couple, situated at 1.23 V versus NHE, pH = 0 (−5.63 eV). [155,161,162] Common strategies to improve photocatalytic performance typically aim 1) to match the HOMO-LUMO to the thermodynamic requirements of the water redox reactions (driving forces for charge transfer), 2) to improve intermolecular packing and charge transport by enhancing the coplanarity of the polymer [163] or increasing the conjugation degree, [164] and 3) to increase the charge density in the system by introducing electron-rich units via copolymerization or blending donor and acceptor type polymers. [165] The work of Sachs et al showed that these properties are however not adequate to enhance the activity alone, but hydrophilicity of the polymer is crucial to favor electron transfer to protons.…”

Section: Fuel Generation From An Aqueous Medium Via Photo or Electrocmentioning

confidence: 99%

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Organic Bioelectronics: From Functional Materials to Next‐Generation Devices and Power Sources

2020

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Conjugated polymers (CPs) possess a unique set of features setting them apart from other materials. These properties make them ideal when interfacing the biological world electronically. Their mixed electronic and ionic conductivity can be used to detect weak biological signals, deliver charged bioactive molecules, and mechanically or electrically stimulate tissues. CPs can be functionalized with various (bio)chemical moieties and blend with other functional materials, with the aim of modulating biological responses or endow specificity toward analytes of interest. They can absorb photons and generate electronic charges that are then used to stimulate cells or produce fuels. These polymers also have catalytic properties allowing them to harvest ambient energy and, along with their high capacitances, are promising materials for next‐generation power sources integrated with bioelectronic devices. In this perspective, an overview of the key properties of CPs and examination of operational mechanism of electronic devices that leverage these properties for specific applications in bioelectronics is provided. In addition to discussing the chemical structure–functionality relationships of CPs applied at the biological interface, the development of new chemistries and form factors that would bring forth next‐generation sensors, actuators, and their power sources, and, hence, advances in the field of organic bioelectronics is described.

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“…[93][94][95] Although these microporous conjugated polymeric networks are not solution processable, they have received widespread attention as photocatalysts for H 2 production owing to their π-conjugated backbones and high porosity. [93,96,97] Their synthesis, outlined in several reviews, [90,98,99] chiefly utilizes kinetically controlled cross-coupling reactions, allowing incorporation of a diverse range of organic semiconductor building blocks to generate amorphous polymer networks. [93,[98][99][100] Varying the ratio of monomers with different connectivities and lengths was shown to be an effective strategy to tune the pore dimensions and surface area of conjugated network polymers in a continuous fashion.…”

Section: Conjugated Network Polymers For Hydrogen Evolutionmentioning

confidence: 99%

Photocatalysts Based on Organic Semiconductors with Tunable Energy Levels for Solar Fuel Applications

Koščo

Moruzzi

Willner

et al. 2020

Advanced Energy Materials

106

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development of sustainable energy sources. [1] Among these, solar energy has the greatest potential, with more solar energy irradiating the surface of the Earth in one hour than human society consumes in one year. [2] However, the intermittency of solar energy limits its utility. In order for solar energy to provide power on a scale commensurate with that currently generated from fossil fuels, it must be stored and supplied to users on demand. [3] On short timescales (seconds to days) this is possible to achieve using batteries, which can store electricity generated from solar photovoltaics. [4,5] However, the expensive materials required and their relatively high rates of self-discharge make batteries unsuitable for seasonal energy storage. [6,7] Storing solar energy in the chemical bonds of a fuel, which can be stored indefinitely at low cost, transported, and converted to electrical or heat energy on demand is therefore highly desirable. Solar fuels such as H 2 , CH 3 OH, and CH 4 can be generated from abundant and renewable feedstocks such as water and CO 2 using semiconductor photocatalysts. The vast majority of research to date has focused on photocatalysts fabricated from wide bandgap semiconductors such as TiO 2 , [8] SrTiO 3 , [9] and carbon nitride (CN). [10-14] Photocatalysts based on some of these semiconductors have achieved operational stabilities exceeding 1000 h and maximum external quantum efficiencies (EQEs) of over 50% for overall water splitting. [9,15-18] However, their wide and difficult to tune bandgaps mean that photocatalysts fabricated from these semiconductors are almost exclusively active at UV wavelengths, which carry <5% of solar energy. [19] This fundamentally limits their efficiency below what is required for many practical solar fuels applications. For example, an estimated solar-to-hydrogen efficiency (η STH) of 5-10% would be required to photocatalytically produce H 2 at a cost that meets the U.S. Department of Energy's target of $2-4 kg −1 , which is difficult or impossible to achieve with the aforementioned wide bandgap semiconductors. [20] This has stimulated interest in developing novel photocatalysts based on semiconductors with narrower bandgaps that are able to absorb a greater proportion of the solar spectrum and can therefore achieve higher maximum theoretical solar energy conversion efficiencies. [18] Among these, non-CN organic semiconductors have recently gained prominence due to the Earth abundance of their constituent elements, and their high extinction coefficients and The photocatalytic synthesis of solar fuels such as hydrogen and methane from water and carbon dioxide is a promising strategy to store abundant solar energy in order to overcome its intermittency. Although this approach has been studied for decades using inorganic semiconductor photocatalysts, organic semiconductors have only recently gained notable attention. The tunable energy levels of organic semiconductors can enable the design of photocatalysts with optimized solar light utilization. However,...

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Conjugated polymers for visible-light-driven photocatalysis

Abstract: This review summarizes the recent advancements in π-conjugated polymers for various photocatalytic applications under visible light.

Cited by 475 publications

References 223 publications

The Bulk Heterojunction in Organic Photovoltaic, Photodetector, and Photocatalytic Applications

The Bulk Heterojunction in Organic Photovoltaic, Photodetector, and Photocatalytic Applications

Organic Bioelectronics: From Functional Materials to Next‐Generation Devices and Power Sources

Photocatalysts Based on Organic Semiconductors with Tunable Energy Levels for Solar Fuel Applications

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