Performance and Solution Structures of Side‐Chain‐Bridged Oligo (Ethylene Glycol) Polymer Photocatalysts for Enhanced Hydrogen Evolution under Natural Light Illumination

Abstract

Converting solar energy into hydrogen energy using conjugated polymers (CP) is a promising solution to the energy crisis. Improving water solubility plays one of the critical factors in enhancing the hydrogen evolution rate (HER) of CP photocatalysts. In this study, a novel concept of incorporating hydrophilic side chains to connect the backbones of CPs to improve their HER is proposed. This concept is realized through the polymerization of carbazole units bridged with octane, ethylene glycol, and penta‐(ethylene glycol) to form three new side‐chain‐braided (SCB) CPs: PCz2S‐OCt, PCz2S‐EG, and PCz2S‐PEG. Verified through transient absorption spectra, the enhanced capability of PCz2S‐PEG for ultrafast electron transfer and reduced recombination effects has been demonstrated. Small‐ and wide‐angle X‐ray scattering (SAXS/WAXS) analyses reveal that these three SCB‐CPs form cross‐linking networks with different mass fractal dimensions (f) in aqueous solution. With the lowest f value of 2.64 and improved water/polymer interfaces, PCz2S‐PEG demonstrates the best HER, reaching up to 126.9 µmol h−1 in pure water‐based photocatalytic solution. Moreover, PCz2S‐PEG exhibits comparable performance in seawater‐based photocatalytic solution under natural sunlight. In situ SAXS analysis further reveals nucleation‐dominated generation of hydrogen nanoclusters with a size of ≈1.5 nm in the HER of PCz2S‐PEG under light illumination.

Indanone-based conjugated polymers enabling ultrafast electron transfer for visible light-driven hydrogen evolution from water

“…Importantly, ICTDB, with its relatively larger s 1 lifetime component, demonstrates the fastest electron transfer ability, along with the least impact of charge recombination among the three photocatalysts. 11,[65][66][67]69,70,73,74 These ndings are consistent with the HER performance of these polymers and underscore the superior charge transfer capability of ICTDB as a photocatalyst.…”

“…Fitting the data with three-exponential functions revealed that all three photocatalysts exhibited two short-lived components and one long-lived component in their decay profiles. 11,67–69 The short-lived components τ 1 , within the picosecond timescale, are likely to signify electron transfer to Pt sites. Conversely, the long-lived component τ 3 is attributed to charge carrier recombination.…”

“…Since the discovery of the application of graphitic carbon nitride in hydrogen evolution in 2009, 1 there has been a surge in research focusing on polymeric semiconductors as potential catalysts. Various types of polymeric materials have been made; for instance, linear conjugated polymers, [2][3][4][5][6][7][8][9][10][11] conjugated microporous polymers, [12][13][14][15][16][17] polymer dots, [18][19][20][21][22][23] covalent triazine frameworks, [24][25][26] and covalent organic frameworks, [27][28][29][30][31][32] have been explored for their photocatalytic properties in hydrogen evolution. These diverse organic semiconductors offer a wide range of properties and functionalities, presenting exciting opportunities for further advancements in PHP technology.…”

“…11,[67][68][69] The short-lived components s 1 , within the picosecond timescale, are likely to signify electron transfer to Pt sites. Conversely, the long-lived component s 3 is attributed to charge carrier recombination.…”

“…11,[60][61][62][63]70 Among the three photocatalysts, ICTDB exhibits the highest proportion s 1 lifetime component, accounting for 82.2% of the total, signifying exceptionally rapid transfer of photoexcited electrons to the Pt sites in ICTDB. Although the s 1 of IDMTDB is slightly shorter than that of ICTDB, the proportion of the s 1 component is signicantly smaller than that of ICTDB, indicating inefficient ultrafast charge transfer compared with ICTDB.…”