Steering Charge Kinetics Behavior Of Polymeric Carbon Nitride And Its Photocatalytic Performance

Semiconductor photo catalytic technology is one of the most feasible solutions for sustainable energy and environmental governance.However,how to develop efficient photocatalysts is an attractive but challenging core issue in today's areas of condensed matter physics.Polymer graphite phase carbon nitride(CN)as the most promising star material in the next generation of organic polymer semiconductor photocatalysts.However,the rapid recombination of photoretic charge in the pristine CN is still the biggest obstacle to its photo catalytic application.Charge dynamics regulation strategies are a promising solution,but most of them are stuck at the macro level.Although some micro-angle charge separation strategies are proposed,there are still challenges of high synthesis and high cost.Therefore,how to develop charge separation strategy based on microcosmic macro angle to accurately regulate charge dynamics is a difficult challenge to develop high-efficiency CN photo/electric catalyst.This paper designs the micro-composition and structure of CN by means of surface engineering,constructing micro-region heterogeneous junctions and improving crystallinity,and changes the distribution of local electric fields and regulates their charge dynamics to improve their photo/electrocatalytic properties.The details of the study are as follows:(1)Herein,we propose a new strategy based on intra-melon hydrogen-binding interactions in 2D CN frameworks to improve its crystallinity.The concept is validated by removing partial amino groups and connecting melon using codoped B atoms via a simple one-step sodium fluoroborate assisted thermal treatment.The enhancement of crystallinity can effectively promote exciton dissociation and charge transfer in CN nanosheets.The highly efficient visible-light photocatalytic activity of the crystalline B/F-codoped CN nanosheets was demonstrated by degrading methyl orange,Rhodamine B and colorless phenol,where degradation rate constant of methyl orange was more than10 times higher than that of pure CN.And,this sample exhibits excellent photoelectrocatalytic performance of oxygen evolution reaction(OER).(2)At first,we develop a novel strategy?a one-step hydroxy-carbonate-assisted route?to try to overcome these disadvantages in CN nanosheets by creating substantial pores ranging from mesoporous to macropore,which are mainly caused by the partial breaking of hydrogen bonds and removing of magnesium oxide.The rich multi-stage hole structure not only fully exposes the reaction active bits at the edge of the pore,but also effectively improves the separation of photo-carriers by shortening the distance of charge transfer.This method has the advantages of simple,low cost,large-scale preparation,to promote macro/micro level collaborative regulation of charge dynamics to provide an optimizing structure and component strategy.Another work proposes a novel strategy—heteroatom-mediated spatial charge separation and transfer—to accelerate photogenerated charge kinetics for boosting the photocatalytic performance of graphitic carbon nitride(CN).Both the experimental results and DFT calculations show that out-of-plane charge transport and in-plane charge separation within CN nanosheets can be accelerated via F intercalation and B intralayer modification.Furthermore,a novel strategy based on controllable in situ surface engineering and morphology is developed to synergistically boost the catalytic activity of CN via tuning the hydroxyl groups on its surface and constructing unique nanostructure.The controllable introduction of hydroxyl groups on CN nanoshells,which is prepared by thermal condensation of oxygen-contained supramolecular precursors formed in water.The results of density general letter theory(DFT)show that the introduction of-OH group not only realizes the spatial separation of MOMO and LUMO,accelerates the process of charge dynamics.The optimized hollow hemispherical CN nanoshells exhibited remarkable catalytic activity,with a photoelectrocatalytic OER overpotential of about 330 m V at a current density of 10 m A cm^-2,outperforming most precious-metal catalyst.This innovative strategy provides a new way for microcosmic and macro-level development of charge separation strategy to accurately regulate charge dynamics.(3)Here,we developed an effective strategy to control?-electron densities in creel-like carbon nitride through C implantation(CN-C)based on the co-polycondensation of a host–guest supramolecular precursor prepared from?-electron-rich oxamide with urea and melamine with cyanuric acid,thereby eliminating the issues in the mismatch of the physicochemical properties of two constituents.The increasing?-electron density realizes the spatial separation of MOMO and LUMO,accelerates the process of charge dynamics,and promotes the separation and transmission of photo-charged carriers within and between laye rs.In addition,the asymmetric CN structure activates the n-?*electron leaping mode,which not only enhances the absorption of visible light,but also increases the migration path of photoelectronics.The CN-C nanocages exhibit remarkable photocatalytic hydrogen evolution activity under visible light exposure with the highest H₂ generation rate of 1135?molh^-1g^-1,which is more 19times above the pristine CN(59.6?molh^-1g^-1).(4)Herein,we developed a novel strategy---simultaneously building two kinds of heterojunctions----to modulate interfacial charge kinetics in polymeric carbon nitride(CN)for improving photocatalytic activity.Using a simple one-step thermal condensation of carbon quantum dots(CQDs)-contained supramolecular precursors formed in water,the controllable CQDs embedded CN nanoframes possessed two kinds of heterogeneous interfaces within seamlessly stitching micro-area two-dimensional in-plane and out-of-plane domains.These two kinds of heterojunctions can effectively enhance its intrinsic driving force to accelerate the separation and transfer of charge along different directions.The remarkable visible-light photocatalytic activity of hollow porous CN-CQDs nanoframes was demonstrated by degrading tetracycline(TC)and rhodamine(Rh B)as models.This work provides a novel strategy of the interface design of heterophase junction with atomic precision.