Biomass Nanomicelles Assist Conjugated Polymers/Pt Cocatalysts To Achieve High Photocatalytic Hydrogen Evolution

Abstract

Conjugated polymers are emerging as promising organic photocatalysts for photocatalytic hydrogen evolution; however, they are suffering from poor water dispersabilities. Herein, this problem is addressed in an easy and green way with the assistance of a biomass-derived material. An amphipathic xylan derivative that can be selfassembled into nanomicelles was employed as carriers to encapsulate a series of conjugated polymers to form uniform composite micelles in water. By this way, the hydrophobic conjugated polymers and their blends were successfully dispersed into water and thus enabling efficient hydrogen evolution. Moreover, the energy level offsets of these conjugated polymers enable the formation of photoinduced charge transfer (PCT) process and fluorescence resonance energy transfer (FRET) process in their composite micelles. The photocatalytic experimental results showed that in these composite micelles, conjugated polymer blends with PCT characteristic delivered much higher photocatalytic hydrogen evolution rates over that of pristine polymer, while conjugated polymer blends with FRET characteristic delivered negligible improvement. Our results demonstrated effective strategies to improve the photocatalytic activity of conjugated polymers, which could also be applied to other photocatalytic materials and systems.

Enhanced photocatalytic hydrogen evolution from organic semiconductor heterojunction nanoparticles

“…[13][14][15] This greatly limits the ηSTH of current Z-schemes and has prompted the recent interest in developing visible light active HEPs based on organic semiconductors other than CNx, 7 whose bandgaps can be tuned to absorb further into the visible spectrum. Conjugated polymers 16,17 and covalent organic frameworks (COFs) 18 have attracted the most attention due to their modular structures which enable their energy levels and physical properties to be precisely controlled. However, the external quantum efficiencies (EQEs) of these novel non-CNx photocatalysts have been limited by the high exciton binding energies and short exciton diffusion lengths (typically 5-10 nm) 19 of organic semiconductors which cause high rates of exciton recombination in the semiconductor bulk, 20 and hence inefficient generation of charges that can drive redox reactions at the photocatalyst surface.…”

“…21,22 Less attention has been given to developing organic non-CNx HEPs with internal semiconductor heterojunctions that can drive exciton dissociation and spatially separate charges in the photocatalyst bulk. 17,23 Conjugated polymer NPs can be readily fabricated with an internal D/A heterojunction by blending donor and acceptor semiconductors together within the same NP. 24 However, this feature has not yet been fully exploited, with most studies to date focusing on optimising the photocatalytic performance of HEP NPs formed of a single conjugated polymer.…”

Hydrophilic Conjugated Materials for Photocatalytic Hydrogen Evolution

“…Reproduced with permission. [44] Copyright 2019, American Chemical Society. (b) Charge transfer processes in heterojunction photocatalysts.…”

“…The construction of an appropriate heterojunction structure is a promising strategy to enhance the charge separation efficiency and increase photocatalytic performance. Zhang et al [44] constructed a series of polymer/polymer heterojunctions for photocatalytic hydrogen evolution using a range of conjugated polymers with different energy levels (PF8, PF8TPA, PFBT, PF8dfBT, PF8DTBT, Scheme 3). The conjugated polymers and their blends were covered by an amphipathic xylan derivative (X-g-NMe), which enables the formation of polymer blend micelles in water (Figure 7a).…”

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

“…Recently, Pt-loaded NPs formed via nanoprecipitation from blends of wide bandgap conjugated polymers were used as photocatalysts for H 2 evolution. [286,287] The highest performing blend consisted of the donor polymer poly[(9,9-dioctylfluorene-2,7-diyl)-alt-(triphenylamine-4,4′-diyl)] (PF8TPA) combined with the acceptor polymer poly(9,9-dioctylfluorene-alt-difluorobenzothiadiazole) (F8dfBT). The blend NPs achieved a HER rate of 7.06 mmol h −1 g −1 , which is 2.5 times greater than a mixture of NPs formed from the individual semiconductors.…”