Molecular Heterostructures of Covalent Triazine Frameworks for Enhanced Photocatalytic Hydrogen Production

Abstract

Conjugated polymers have emerged as promising candidates for photocatalytic H2 production owing to their structural designability and functional diversity. However, the fast recombination of photoexcited electrons and holes limits their H2 production rates. We have now designed molecular heterostructures of covalent triazine frameworks to facilitate charge‐carrier separation and promote photocatalytic H2 production. Benzothiadiazole and thiophene moieties were selectively incorporated into the covalent triazine frameworks as electron‐withdrawing and electron‐donating units, respectively, by a sequential polymerization strategy. The resulting hybrids exhibited much improved charge‐carrier‐separation efficiency as evidenced by photophysical and electrochemical characterization. An H2 evolution rate of 6.6 mmol g−1 h−1 was measured for the optimal sample under visible‐light irradiation (λ>420 nm), which is far superior to that of most reported conjugated‐polymer photocatalysts.

Heat Diffusion‐Induced Gradient Energy Level in Multishell Bisulfides for Highly Efficient Photocatalytic Hydrogen Production

“…Hydrogen production via photocatalytic water splitting is known to be one of the most prospective and effective methods to battle the current global energy and environmental crisis. [ 1–8 ] However, to date, the best performing photocatalysts still suffer from relatively low solar‐to‐hydrogen conversion, to levels that lie far below the demand for practical applications. [ 6,8–11 ] The low efficiency of photocatalytic water splitting is attributed to three main reasons: i) the low utilization of sunlight, ii) the poor efficiency of separation and transfer of photogenerated carriers, and iii) sluggish kinetics of the hydrogen evolution reaction.…”

“…So far, a favorable library of morphological structures has been devised in semiconductor photocatalysts, containing 0D quantum dots, [ 22,23 ] 1D nanowires/nanorods, [ 8,24,25 ] 2D nanosheets, [ 1,12,13 ] 3D hollow nanostructures, [ 21,26 ] and heterostructures. [ 5,6,17 ] Among them, precisely designed hollow multishell structures possess attractive characteristics for photocatalysis, including efficient light harvesting, improved charge transfer, and high specific surface area. [ 17,21,27–32 ] Single/multishell hollow spheres, [ 18,33,34 ] hollow cubes, [ 35–37 ] egg yolk shells, [ 27,36,38 ] and other shaped hollow spheres have been reported.…”

Unraveling the Photocatalytic Water Dissociation Pathways on Two‐Dimensional Conjugated Polymers

“…Converting solar energy into storable chemical fuels via photocatalytic water splitting is a potentially viable route toward producing clean and sustainable energy in the future . In particular, photocatalytic overall water splitting, which can decompose pure H 2 O into stoichiometric amounts of H 2 and O 2 without using any sacrificial agents, is fundamentally important but still remains challenging . Compared to inorganic semiconductors, metal‐free polymers represent an emerging class of photocatalysts for photocatalytic overall water splitting .…”

Highly efficient charge transfer in CdS-covalent organic framework nanocomposites for stable photocatalytic hydrogen evolution under visible light

“…Previous studies have revealed that the p-stacked structure of COFs provides them with defined pathways for charge carrier transport [26][27][28]. This, in combination with the large surface area, adjustable porosity and tailorable chemistry, has enabled COFs to show a variety of potential applications.…”