Metal?Ag,K,Au?Tune The Electronic Structure In G-C₃N₄:Photocatalytic Activity Enhancement And Its Reaction Mechanism

In recent years,graphite-like carbon nitride?g-C3N4?has exhibited good photocatalytic advantages,and it is widely used in visible light photocatalysis applications,However,the internal structure defects of g-C₃N₄ lead to its lack of forbidden band width,high photogenerated charge recombination rate,less active sites and lower visible light utilization efficiency,which limits its application in the field of photocatalysis.The purpose of this paper is to reduce the structural defects and hydrogen bonding of g-C3N4 by doping with metal elements and to spatially suppress the high polymerization superposition of the melon unit?conjugate system,thereby regulating the internal electronic structure of g-C₃N₄?including the in-plane electronic structure and the interlayer electronic structure?induces the directional transmission of photogenerated charges,realizes efficient photo-generated carrier separation efficiency to promote photocatalytic performance,and also realizes effective regulation of the band gap structure and the number of active sites.The specific research contents of this paper are as follows:?1?Ag-introduced CN?AgCN?samples were designed as photocatalysts by introducing Ag into CN to weaken the planar hydrogen bonding for photocatalytically eliminating methyl orange pollutant.Spectroscopy,electrochemistry and computational studies revealed that AgCN photocatalyts presented a significantly enhanced sunlight absorption,efficient carrier mobility as well as improved O₂ adsorption state.As a result,photoreactivity for methyl orange photooxidation elimination over AgCN was significantly enhanced,with apparent rate of 0.13 min^-1 for optimal AgCN-4 under visible-light irradiation,which was6.50,8.13,2.60,and 4.33 times that of g-C₃N₄(0.04 min^-1),Bi₂WO₆(0.02 min^-1),BiOCl(0.016 min^-1),Ag/CN(0.05 min^-1)and Ag₂CO₃(0.03 min^-1),respectively.The result supplied an efficient approach for constructing effective visible-light-irradiation photocatalysts for environmental purification.?2?Solid strong base systems of g-C₃N₄ by inducing potassium?KC₃N₄?were constructed for photocatalytically decomposing HCHO.Characterization and theoretical calculation revealed that the formation of K-C and K-N perfected the?-conjugated structure of g-C₃N₄,which greatly enhanced the basicity,improve optical and electrical properties of g-C₃N₄.In the photocatalytic process,K-improved?-conjugated structure promoted HCHO adsorption,activation,completely oxidative decomposition under visible-light irradiation.Therefore,KC₃N₄ photocatalysts presented high efficiency in photocatalytic elimination of HCHO,and the optimal apparent rate reached 0.21 mol^-0.17·L^0.17·min^-1 with 1.17 reaction order by promoting the reaction between active oxygen?-OH and·OH?and formate species under visible-light irradiation,which was 30 times of that(0.007 mol^-0.17·L^0.17·min^-1 over pristine g-C₃N₄.These results may suggest a new way for probing the advanced solid strong base photocatalysts for eliminating volatile organic compounds.?3?graphene-like carbon nitrides combined with Au nanoparticles?AuCN?photocatalysts were facilely constructed by Au-induced space-inhibited superposition of layers.Based on series characterizations,AuCN photocatalysts were confirmed to possess the increased potentials of valence and conduction bands with enhanced plasmonic visible-light absorption and efficient charge transfer.Under visible-light irradiation,more photogenerated electrons can be not only transferred from N 2p but also from N 2s orbitals of valence band?VB?to C 2p and N 2p orbitals of conductor band?CB?with the promoting effect of the graphene-like structure of AuCN with plasmonic Au.Therefore,AuCN photocatalysts displayed greatly enhanced photocatalytic activities for gaseous HCHO decomposition and aqueous MO elimination by the·OH and·O₂^-oxidation mechanism,in comparison with bulk g-C₃N₄.