| In recent years,TiO2,MoS2and MoSe2 have been widely used in the field of catalysts.However,their application in the field of photocatalysis is very limited because the band gap of TiO2 is large,and the photocatalytic active sites of MoS2 and MoSe2 exist only at the edge of the material.Doping is considered to be an effective method to solve the above problems and improve the photocatalytic activity of materials.This topic mainly introduces the influence of metal or non-metal doping on the photocatalytic activity of materials.The details are as follows:(1)The crystal structure,formation energy,electronic and optical properties of undoped,Co,N doped and co-doped TiO2 were investigated by first principles calculations.Considering the potential of water redox reaction of these systems indicate that only N-,Co-1N-and Co-2N co-doped TiO2 meet the requirement of the photosplitting water.Moreover,the optical absorption threshold and absorption area of Co-2N co-doped TiO2 are obviously enlarged compared with the undoped TiO2.Co-2N co-doped TiO2 has the highest light absorption efficiency and hydrogen production efficiency,due to the presence of curved and broad impurity levels that greatly improve the carriers'mobility and separation.(2)The crystal structure,formation energies,electronic structures and effective masses of charge earriers of N/F co-doped anatase TiO2 were investigated by first principle calculations.We have found that the incorporation of the N atom will be easier in the presence of the F dopant.Second,the impurity band of N/F co-doped TiO2 has no spin polarization and smaller effective mass.which improves the photogenerated carriers'mobility and separation.Moreover,it has lower band edge energy,which increases the oxidation ability of the photogenerated holes.Thus,we explained the mechanism of the enhancement of photocatalytic efficiency of N/F co-doped TiO2 observed by experiments.(3)Recently,P doped ultra-thin MoS2 film has demonstrated enhanced photocatalytic property.However,the flat impurity level within the bulk band gap acting as the recombination center hinders the photocatalytic performance.This impurity level is induced by P.Thus,charge compensated doping P and Cl together is adopted here to remove the impurity levels.It is found that P and Cl atoms tend to settle at S sites(PS and ClS)instead of Mo sites or interstitial.Interestingly,PS-ClS co-doping can enhance the photoeatalytic activity of MoS2 by removing the flat impurity level and increasing the number of catalytic active sites.(4)The geometrical structure,redox potentials,electronic and photocatalytic properties of nonmetal(H,B,C,Si,N,P,As,O,S,Te,F,Cl,Br and I)doped monolayer MoSe2 were investigated by first principle calculations.The binding energy indicates that nonmetal doped MoSe2 are energetically favorable compared to Se vacancies,except B-and C-doped.Nnonmetal dopants with an odd number of valence electrons doped MoSe2 have better photocatalytic performance.(5)Using fir-st-principle calculations,we have systematically investigated the enhancement of photocatalytic activity in nonmetal(NM)(B,C,Si,N,P and As)doped monolayer MoSe2 after hydrogen(H)passivation.We have found that incorporation of the NM atoms into MoSe2 will be easier in the presence of H.Moreover,H-passivation can enhance the photocatalytic activity of doped MoSe2 by suppressing the recombination of photogenerated electron/hole pairs and increasing the reduction ability of photogenerated electrons,especially in C-2H doped MoSe2.(6)The electronic and photocatalytic properties of 3d transition metal(TM)doped(Sc,Ti,V,Cr,Mn,Fe,Co,Ni,Cu and Zn)2H-MoSe2 were investigated by first-principles calculations.The results indicate that Sc,Ti,V,Cr.Mn,Fe and Co atoms tend to substitute the Mo atoms under Se-rich condition,while Ni,Cu and Zn atoms prefer to occupy the interstitial positions.More importantly,Sc-and Ti-doped 2H-MoSe-2 can enhance the photocatalytic activity by increasing the oxidizability of photogenerated holes,suppressing the recombination of photogenerated carriers and increasing the number of catalytic active sites... |
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