Progress of crystalline carbon nitride in synthesis,atomic structure characterization and photocatalysis

Crystalline carbon nitride(CCN)has emerged as a highly promising semiconductor photocatalyst with unique properties,such as enhanced charge migration rate,reduced carrier recombination probability,narrow band gap and improved light-harvesting efficiency,which are suitable for a wide range of applications in solar-to-chemical conversion,energy storage,therapeutic and environmental pollution degradation.In the past few years,there has been an increasing number of reviews on CCN materials.However,most of these reviews mainly focus on synthesis methods,modification and applications,with less emphasis on the relationship between structures and properties,as well as on indepth exploration of the crystalline structure.The electronic instability of CCN presents challenges for conventional characterization techniques to directly and thoroughly investigate the relationship between its intrinsic atom structure and photocatalytic performance.This mini-review not only highlights the progress in CCN-based photocatalysts,with a focus on molten-salt synthesis(including solid-salt-induced crystallization),but also emphasizes the atomic structure characterization by specifically introducing the differential phase contrast(DPC)scanning transmission electron microscopy(STEM)technique,which is essential for enhancing our understanding of the crystal structure and photocatalytic mechanisms of CCNs.Additionally,the review outlines the photocatalytic performance and puts forward potential challenges on CCN studies.This review will provide a clearer understanding of the relationship in developing precise customization strategies for CCN materials and ultimately explain the regularity and specificity of the enhanced performance in targeted photocatalytic systems.

In-depth Understanding of the Effects of Intramolecular Charge Transfer on Carbon Nitride Based Photocatalysts

Intramolecular charge transfer(ICT)derived from a donor-acceptor system has been applied for years to enhance the charge mobility in the field of organic photovoltaics and chemical sensing.Similar strategies have gradually been developed in polymeric graphitic carbon nitride(GCN)photocatalytic systems for promoting the light absorption and charge separation.However,there are no reviews focusing on the effects of ICT after the modification of GCN so far.Herein,we summarize some typical literature on GCN engineering to expound profoundly the roles of ICT in electronic properties regulation in terms of in-situ formation and molecular coupling.At last,some important perspectives are also proposed.This review will deepen understanding of the traditional theory for a new recognition among such many methods to improve the performance of GCN.

A facile method to introduce a donor-acceptor system into polymeric carbon nitride for efficient photocatalytic overall water splitting

It is a prospective strategy to produce sustainable energy by photocatalytic overall water splitting(POWS).This work aims to develop a simple method for integrating a donor-acceptor system into polymeric car-bon nitride(PCN)structure,which could accelerate the charge separation significantly.In the as-prepared photocatalyst(COCNT),carbon and oxygen were successfully incorporated into the framework of PCN,and the chemical environment of C and O was well probed by X-ray absorption near-edge structure(XANES)and X-ray photoelectron spectroscopy(XPS).It showed that the C-containing and O-containing segments of COCNT played the role of a donor,while the heptazine part played the role of an acceptor.In addition,Density-functional-theory(DFT)calculations confirmed the spatial split of the highest occupied molec-ular orbital(HOMO)and lowest unoccupied molecular orbital(LUMO)for promoting charge separation.Impressively,COCNT could efficiently split pure water to generate hydrogen and oxygen.And,the photo-catalytic hydrogen evolution rate over COCNT(1550.9μmol g^(-1)h^(-1))is about 17-fold higher than that of PCN.Finally,we proposed a possible photocatalytic mechanism to explain the above results.