Synthesis And Property Research Of G-C₃N₄-based Photocatalysts

Graphitic carbon nitride(g-C3N4),as a metal-free and visible-light-responsive photocatalyst,has become a new research hotspot in the arena of solar energy conversion and environmental remediation.Since 2009,an enormous amount of research has mainly focused on optimizing highly efficient g-C3N4-based photocatalysts for the splitting of water into hydrogen gas.In recent years,the application of g-C3N4 as photocatalytic CO2 reduction has also largely developed.However,the primary g-C3N4 usually exhibits limited utilization for visible light and the fast combination of photoexcited charge carriers,resulting in the low photocatalytic ability.Several strategies have been proposed to address above mentioned issues,including molecule incorporation,morphology regulation,as well as band-engineer controlling.Therefore,in this paper,we prepared g-C3N4-based phptocatalysts to improve its photocatalytic activity.(1)A new g-C3N4-based photocatalyst simultaneously containing nitrogen vacancies and oxygen-doping is successfully developed by using two-step post-synthetic strategy for photocatalytic H2 evolution,resulting in greatly-boosted H2 evolution activity(1689 ?mol g-1 h-1)comparing with that of pristine g-C3N4(112 ?mol g-1h-1).The modification endows carbon nitride materials with enhanced optical absorption,accelerated charge carriers transfer rate and the increased hydrogen evolution rate.It is believed that the newly developed double-defect strategy may open an avenue toward obtaining molecular level comprehension into the function of catalyst in photocatalytic H2 evolution and can be extended to the modification of other semiconductors.(2)We first realize the homogeneous decoration of B-H into the MOF and then assembly the developed MOF with carbon nitride nanosheet,resulting in the construction of elegant photocatalyst for CO2 reduction.The developed photocatalyst preferably captures CO2 and further photoreduces CO2 with high efficiency under visible-light irradiation.The photo-generated excitions from carbon nitride nanosheet can directionally migrate to B-H bonding,which effectively suppress electron-hole pair recombination and thus greatly improve the photocatalytic ability.Comparing with g-C3N4 nanosheet,the BIF-20@g-C3N4 nanosheet composite displayed a much-enhanced photocatalytic CO2 reduction activity,which is equal to approximately 10-fold enhancements in CH4 evolution rate(16 ?molg-1h-1)and approximately 10-fold improvements in CO generation rate(54 ?mol g-1h-1).Density functional theory(DFT)calculations further prove that the presence of B-H bonding in the composite is favorable for CO2 adhesion and activation in the reaction process.Thus,we believe that the implantation of functional active sites into porous matrix provides important insights for preparation of efficient photocatalyst.We anticipate that this elegant decoration strategy combined with these molecular material platforms will be applicable to a broad range of catalytic applications,particularly to those that require solar harvesting and gaseous compatibility.