Trithiocyanuric Acid Aggregate As A Photocatalyst For Hydrogen Production

Photocatalytic splitting of water to produce hydrogen is considered to be one of the effective means of achieving solar energy storage.The structure of semiconductor photocatalytic materials controls photophysical processes such as photon absorption and charge separation,which has an important impact on photocatalytic activity.After decades of development,scientists have developed a large number of semiconductor photocatalytic materials,however,the activity of most reported photocatalytic materials is still low,and the development of new and efficient photocatalytic materials has always been the focus of research in photocatalysis discipline.Organic semiconductor photocatalytic materials have attracted extensive attention because of their easy tunability in terms of structural composition and electronic properties.The organic semiconductor photocatalytic materials that have been reported are mainly composed of one or several structural units linked by covalent bonds.In principle,weak intermolecular interactions may also induce electronic coupling between molecules,which in turn leads to new functions that are different from those of monomeric molecules.In this paper,it was found that trithiocyanuric acid hydrogen bond aggregate(ATA)has good visible light absorption properties,and has the function of visible light photocatalytic water splitting to produce hydrogen.Based on this,a series of novel aggregate photocatalytic materials were developed by combining theoretical calculations and simulations.The details of the research are as follows:(1)The powder aggregates formed by the hydrogen bonding(N-H???S)interactions between trithiocyanuric acid molecules were found to have good visible light absorption properties,with a light absorption edge of 461 nm.The results show that the relatively weak interaction between the trithiocyanuric acid molecules in the aggregate leads to rich and distorted structure,which makes the non-bonding 2p orbital occupied by the lone pair of electrons on the S atom and the π orbital of the triazine ring have a large degree of spatial overlap,and activates the low-energy and usually forbidden n→π* electron transition,so as to achieve effective capture of visible light.At the same time,the aggregate structure favours charge delocalization and significantly prolongs the lifetime of photogenerated charge.Band structure analysis found that the trithiocyanuric acid powder aggregate fully met the thermodynamic requirements of photolysis water.Therefore,ATA achieves high efficiency in driving water splitting to hydrogen production under visible light,with performance comparable to that of organic conjugated polymer photocatalytic systems.(2)On the basis of the above,we synthesized oxygen-doped trithiocyanuric acid aggregate photocatalyst(O-ATA)by photochemical method.The oxygen doping can significantly modulate the electronic structure of the aggregate,and the light absorption of O-ATA can be expanded to the red light region,enabling the photocatalytic splitting of water to produce hydrogen under the irradiation of long-wavelength visible light(red light).In addition,we selected small heterogenous molecules(such as adenine,cytosine,xanthine,etc.)that can form hydrogen bonds with trithiocyanuric acid,and modulated the electronic structure of trithiocyanuric acid aggregates by in situ implantation of small heterogenous molecules.Experimental and theoretical results showed that the functionalization of these small molecules all increased the hydrogen production rate of ATA to different degrees,among which xanthine was the most effective,and the hydrogen production rate increased by 2.6 times.(3)Further,more than 80 non-covalent aggregates containing sulfur/oxygen/nitrogen heteroatoms were predicted by computational simulations to possess possible photocatalytic functions.Among them,it was experimentally demonstrated that 8 small molecule powder aggregates,namely 6-mercaptopurine,4,6-diamino-2-mercaptopyrimidine,3-mercaptobenzoic acid,2-mercaptobenzothiazole,2-thiobarbituric acid,2-nitrobenzoic acid,3-nitroaniline,and p-phenylkun,have similar n→π* electron transition properties and photocatalytic function,which greatly enriched the family of visible light responsive photocatalytic materials and opened up new directions for This has opened up a new direction for the research of photocatalytic materials.