Modification Of Polymer Carbonitride Material And Its Application In Photocatalytic Redox Reaction

Nowadays,environmental problems and the energy crisis have become hot issues.The hydrogen evolution by photocatalytic water decomposition is one of the most promising methods to solve both problems.In addition to the hydrogen evolution,the effectively utilization of photogenerated hydrogen and oxygen could develop a series of green oxidation and reduction reactions for artificial photosynthesis of value-added fine chemicals.However,for the current photocatalytic reaction,there are mainly two obstacles.One is the low efficiency of solar energy utilization,and the other is the lack of a low-cost and high-activity semiconductor catalyst.In this regard,the development of new photocatalysts with high quantum efficiency,high visible light utilization,high stability and low cost has become the central issue to researchers.Recently reported polymeric carbon nitride(PCN)is one of the promising semiconductors for high effient photosynthesis.As a new generation of metal-free photocatalysts,it is low cost and has a suitable band structure with visible light absorption.However,the pristine PCN synthesidzed by traditional calcination method has many drawbacks such as low surface area,poor crystallinityand easily recombination of photogenerated electrons and holes.Those disadvantages result in a low photocatalytic activity,which hinder the further application of PCN.In order to solve these problems,in this work,several modified PCN were synthesized by an assistant of solid salt templet and co-doping method with heteroatom.Firstly,the surface area of PCN can be enlarged by co-doping with Se atoms,thus the photocatalytic activity of oxidation reaction was greatly improved.On the other hand,with the ion thermal method a highly crystalline PCN was synthesized.The solid salt can act as a template to promote the precursor of carbon nitride growing along the specific direction under high temperature calcinations.Thus,greatly improve the polymerization process and crystallinity.With good crystallinity,the light adsorption of PCN was enhanced and the band gap was futher optimized.Moreover,the recombination of excitation electrons and holes were decreased,thus promote the catalytic activity of hydrogen evolution.In addition,the photocatalyitic applications of PCN have been further expanded.Currently,the most of PCN applications are mainly focus on the photocatalytic water splitting,reduction of carbon dioxide,and photoelectronic devices.However,the artificial photosynthesis based on water splitting technology using PCN as catalyst was barely reported.Usually,excitation electrons and holes could be generated by the illumination of light.Base on the effectively utilizing the photogenerated electrons and holes with strong reducibility and oxidizability,respectively,several oxidation and reduction reactions could be developed,such as alkenes and alcohol oxidation,alkenes and alkynes hydrogenation.More importantly,using D2O to replace H2O,photogenerated deuterium from heavy water splitting can be used for the selective synthesis of deuterium-labelled fine chemicals and drugs.At the same time,the PCN material can also catalyze the reduction of the nitro group to an amino group,and further realize the N,N-methylation reaction of the amino group.