Reducing the Exciton Binding Energy of Donor–Acceptor‐Based Conjugated Polymers to Promote Charge‐Induced Reactions

Abstract

Exciton binding energy has been regarded as ac rucial parameter for mediating charge separation in polymeric photocatalysts.M inimizing the exciton binding energy of the polymers can increase the yield of charge-carrier generation and thus improve the photocatalytic activities,b ut the realization of this approach remains ag reat challenge. Herein, aseries of linear donor-acceptor conjugated polymers has been developed to minimizethe exciton binding energy by modulating the charge-transfer pathway. The results reveal that the reduced energy loss of the charge-transfer state can facilitate the electron transfer from donor to acceptor,a nd thus,m ore electrons are ready for subsequent reduction reactions.The optimizedpolymer,FSO-FS,exhibits aremarkable photochemical performance under visible light irradiation.Hydrogen evolution using nanoparticulate semiconductors has great potential for future green and sustainable fuel production from water and sunlight. [1, 2] Conjugated polymers (CPs), including carbon nitride, [3] COFs, [4] CTFs, [5] CMPs, [6] and linear polymers, [7] have recently emerged as anew family of semiconductor photocatalysts,o wing to their advantages, such as tunable structure and properties,e ase of fabrication, environmental friendliness,a nd absence of noble metals.T o date,c onsiderable advances have been achieved by rational design of the structure and by tailoring of the properties of the CPs. [8] Nevertheless,because of their undesirably high exciton binding energy (E b ,t ypically > 100 meV), [9] most of the polymeric photocatalysts show only moderate photocatalytic activities,p articularly in comparison with their inorganic counterparts.Recently,i nspired by the rapid charge transfer in donoracceptor (D-A) heterojunction based solar cells,such aD-A construction has also been applied to boost the charge mobility of conjugated polymeric photocatalysts by controlling the local structure of the polymers. [10] It is well established that in aD -A based CP,t he charges tend to spontaneously migrate to the acceptor because of the larger energy of the light-excited excitons (E exc )c ompared to those of the charge transfer (CT) state (E CT )a nd E LUMO of the acceptor (see Scheme 1a). [11] Clearly,the overall amount of charge arriving Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Photocatalyst Z-scheme system composed of a linear conjugated polymer and BiVO4 for overall water splitting under visible light

“…[21][22][23][24] Most photocatalysts so far have been inorganic materials, but organic photocatalysts have attracted growing attention 25 because they can be prepared from earth-abundant elements and their properties-and in particular their light absorption spectrum-can be tuned easily and continuously by co-polymerisation. [26][27][28][29][30][31][32][33][34] However, most polymer studies have been conned to the sacricial half-reaction that produces hydrogen only, and few organic photocatalysts have been developed for overall water splitting. Carbon nitrides have been coupled with WO 3 , which acts as an O 2 evolution photocatalyst in a Z-scheme system for overall water splitting, 26,27,35 but the efficiencies were limited by the commonly observed back reaction.…”

A Tandem 0D/2D/2D NbS2 Quantum Dot/Nb2O5 Nanosheet/g‐C3N4 Flake System with Spatial Charge–Transfer Cascades for Boosting Photocatalytic Hydrogen Evolution

“…[40] By contrast with CN, the fluorescence of Nb 2 O 5 /CN is partially quenched, suggestive of suppression for charge recombination. [41] Astonishingly, NSNOCN displays the lowest PL emission-peak intensity, strongly indicating that the formation of spatial charge-transfer cascades is highly conducive to the acceleration of charge transfer. Transient photocurrent responses further support such results.…”

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

“…[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. [166] Introducing hydrophilic units increased polaron yields thanks to the organization of water around the polymer, whose polarity accelerated the electron transfer step.…”