Doping Ions On Graphitic Carbon Nitrides For Enhanced Photocatalysis: Are You Ready To Join In Hands On A Green Sustainable Avenue?

With the depletion of conventional energy,sunlight-dynamic photocatalysis makes hydrogen production derived from ubiquitous water a reality,which achieves a solar to chemical energy conversion.Graphitic carbon nitride(g-CN),similar to graphene,is composed of in-plane tri-s-triazine repeating units and van der Waals junction between layers.As a new kind of organic polymer,g-CN has exhibited an appealing electronic structure,high stability in the photoreaction,and earth-abundant nature.Graphitic carbon nitride(g-CN)typifies organic semiconducting photocatalyst,but it suffers from inefficient charge transfer and unconsummated polymerization at a certain level.In order to develop an optimal setup of charge distribution in a specific crystal plane,we attempted to realize both crystallinity and doping at the same time.Taking account into three different types of melem-based precursors(melem,oligomelem and melon),we systematically investigated a Zn-doped conjugated system using a two-step thermal polymerization strategy of a molten salts bath.The as-prepared Zn-doped crystalline carbon nitrides(Zn-CCN)show a highly ordered crystal structure with an extended tri-s-triazine-based intraplanar network,improved light harvesting and significantly suppressed electron-hole recombination.In addition,the density functional theory(DFT)calculations revealed that the Zn atoms prefer to dwell in the cave of the(100)plane,and their 4s-orbital electrons directly participate in the formation of the conduction band.This unique Zn-doped electronic structure notably reduces the in-planar charge density when Zn atoms act as a rope ladder urging electrons to escape from the N-encircled cave.When Zn-CCN is tailored with these unique layouts,it exhibits dramatically enhanced visible-light photocatalytic hydrogen evolution and excellent cycling stability,exceeding most of other metal-induced crystalline carbon nitrides.It is anticipated that this work can pave a novel research path in future studies of g-CN-based and other two-dimensional photocatalysts with ameliorated performances.