Conjugated Polymers with Oligoethylene Glycol Side Chains for Improved Photocatalytic Hydrogen Evolution

Abstract

Summary Conjugated polymers are emerging as promising organic photocatalysts for hydrogen evolution from water. However, it is still very challenging for conjugated polymers to realize highly efficient photocatalytic hydrogen evolution. Herein, we demonstrate an efficient strategy of hydrophilic side chain functionalization to boost the hydrogen evolution rates of conjugated polymers. By functionalizing conjugated polymers with hydrophilic oligo (ethylene glycol) monomethyl ether (OEG) side chains, a 90-fold improvement in hydrogen evolution rate has been achieved than that of alkyl-functionalized conjugated polymer. It is found that the OEG side chains interact robustly with Pt co-catalysts, resulting in more efficient charge transfer. Moreover, OEG side chains in conjugated polymers can adsorb H + from water, resulting in significantly lowered energy levels on the surfaces of conjugated polymers, which enables cascade energy levels and enhances charge separation and photocatalytic performance. Our results indicate that rational side-chain engineering could facilitate the design of improved organic photocatalysts for hydrogen evolution.

Side-chain tuning in conjugated polymer photocatalysts for improved hydrogen production from water

“…Recent studies have shown that polymer hydrophilicity is an important factor in determining photocatalytic performance. [29][30][31][32] The incorporation of polar moieties such as dibenzo [b,d]thiophene sulfone 33 or nitrogen substituted benzenes 34 into the polymer backbone substantially improves the interaction with water. This in turn enhances the hydrogen evolution activity, partly by stabilizing the charge-separated state that is produced by hole transfer to the hole scavenger following photoexcitation of the polymer.…”

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

“…5 Conceptually, direct hydrogen production using photocatalyst suspensions is the simplest water-splitting approach in technological terms and it is potentially amenable to large-scale deployment. [7][8][9][10][11][12][13][14][15][16][17] Recently, several examples of photocatalysis has been reported as a one-step overall water splitting. [18][19][20] However, recombination of electron-hole pairs tends to decrease the photocatalytic reaction efficiency.…”

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

“…[166] Introducing hydrophilic units increased polaron yields thanks to the organization of water around the polymer, whose polarity accelerated the electron transfer step. [166,167] Overall, the thermodynamic potentials for the redox reactions, the local environment and the driving forces for individual charge transfer steps are key factors to take into consideration when designing CPs for photocatalysts.…”

“…[171] Hu et al synthesized conjugated backbones comprising a difluorobenzothiadiazole unit alongside a benzodithiophene unit functionalized with oligo ethylene glycol (OEG) side chains to boost photocatalytic performance. [167] The side chains improved the surface wettability with water, adsorbed protons and lowered the flat band potential, while interacting efficiently with the Pt co-catalyst. [172] The side chain engineering led to a dramatic 90-fold increase in the H 2 evolution rate compared to the alkyl analogue of the same backbone.…”