Main-chain engineering of polymer photocatalysts with hydrophilic non-conjugated segments for visible-light-driven hydrogen evolution

Abstract

Photocatalytic water splitting is attracting considerable interest because it enables the conversion of solar energy into hydrogen for use as a zero-emission fuel or chemical feedstock. Herein, we present a universal approach for inserting hydrophilic non-conjugated segments into the main-chain of conjugated polymers to produce a series of discontinuously conjugated polymer photocatalysts. Water can effectively be brought into the interior through these hydrophilic non-conjugated segments, resulting in effective water/polymer interfaces inside the bulk discontinuously conjugated polymers in both thin-film and solution. Discontinuously conjugated polymer with 10 mol% hexaethylene glycol-based hydrophilic segments achieves an apparent quantum yield of 17.82% under 460 nm monochromatic light irradiation in solution and a hydrogen evolution rate of 16.8 mmol m −2 h −1 in thin-film. Molecular dynamics simulations show a trend similar to that in experiments, corroborating that main-chain engineering increases the possibility of a water/polymer interaction. By introducing non-conjugated hydrophilic segments, the effective conjugation length is not altered, allowing discontinuously conjugated polymers to remain efficient photocatalysis.

Three-Component Donor−π–Acceptor Covalent–Organic Frameworks for Boosting Photocatalytic Hydrogen Evolution

“…The signal intensity increased significantly when COF-JLU35 and COF-JLU36 were excited by light due to the formation of more unpaired photogenerated electrons. Such signals were still obtained for both COFs under the dark, which can be attributed to the fact that they responded to light when stored under ambient conditions . Importantly, the signal intensity of COF-JLU35 far exceeds that of COF-JLU36; this can be attributed to the finding that fully π-conjugated frameworks have better stabilization and delocalization of the unpaired electrons .…”

Impact of Interfaces, and Nanostructure on the Performance of Conjugated Polymer Photocatalysts for Hydrogen Production from Water

“…However, the optimum conjugation length remains unclear in the literature so far, thus the design to break the conjugation was rationalized with conveniently hydrophilic segments that do not allow conjugation to extend. This strategy increases the interface between the aqueous environment and the photocatalyst, whilst maintaining localized conjugation lengths throughout the chain [ 100 ]. In this context it is important to mention that even short oligomers have been reported to have high activity for sacrificial hydrogen production [ 11 ] as well as polymers with alkyl-linkers in the backbone [ 70 ].…”

“… ( a ) Schematic illustration of the polymer photocatalysts containing hydrophilic non-conjugated segments; ( b ) Structures of hydrophilic segments and polymer repeat units [Figure adapted from ref. [ 100 ] under CC-BY 4.0 License]. …”

Organic small molecular heterostructures for enhanced photocatalytic hydrogen evolutionviaisomer engineering

“…Global environmental and energy issues have resulted in unprecedented urgency in the exploration for alternative sources of renewable and clean energy. 1–4 Semiconductor-based photocatalysis via water reduction is of great significance for immediate conversion of renewable and green solar energy into high-density and value-added chemical fuels. 5–7 This technology is key to developing excellent photocatalysts with defined molecular structures and efficient hydrogen production ability.…”