Conjugated Crosslinking Modification of Graphitic Carbon Nitrides and Its Effect on Visible Light-Driven Photocatalytic Hydrogen Production

Conjugated Polyelectrolyte Photocatalysts: The Use of Zwitterionic Side Groups for High Performance

“…In this regard, solar-driven photocatalytic hydrogen production from water has attracted increasing attention because it converts solar energy into chemical energy and stores it in hydrogen, a green energy fuel featuring easy storage, transportation, and no pollution after combustion. − Although inorganic semiconductor-based photocatalysts dominate the studies since the first report in 1972, organic semiconductors have emerged as a class in the past decade with advantages in structural diversity and tunability, on-demand designability, and synthesizability. Also, the enormous efforts endeavored so far have successfully developed a variety of organic semiconductor photocatalysts, including linear conjugated polymers (LCPs), − graphitic carbon nitrides (g-C 3 N 4 ), − conjugated microporous polymers (CMPs), − covalent organic frameworks (COFs), − and covalent triazine frameworks (CTFs) − with the record hydrogen evolution rate (HER) exceeding 323.22 mmol g –1 h –1 and apparent quantum yield (AQY) at certain optical wavelength larger than 10% . However, when it comes to the total solar-to-hydrogen energy conversion efficiency, the current state-of-the-art level is still very low and requires significant improvement.…”

“…In the fields of organic solar cells, field-effect transistors, and light-emitting diodes, long alkyl side chains are generally selected for achieving suitable solubility, solution-processability, and regulation on interchain interactions and packing structures in condensed states. − But in the field of organic photocatalysts, they are not welcomed because the augmented hydrophobicity is not good for photocatalysis in a water medium. Therefore, short or even no alkyl side chains are often found in the reported organic photocatalysts. − ,,,− This creates some difficulties in material syntheses and structure characterizations because of the poor solubilities of products and intermediates. Recently, there has been a growing interest to use conjugated polyelectrolytes (CPEs) as photocatalysts. − This is because the ionic side chains in CPEs can endow the material with good water solubility or dispersibility, improve the accessibility of catalytic surface and reactive sites toward reactive species in water, and thus facilitate photocatalysis in water medium.…”