First-principles study on the co-adsorption of water and oxygen molecules on chalcopyrite(112)-M surface

Chalcopyrite is a common copper-bearing mineral with antiferromagnetic properties.However,this property has rarely been considered in previous studies for detailed adsorption behaviors of molecules on chalcopyrite.Based on density functional theory(DFT),new adsorption pathways by H_(2)O and O_(2)on the chalcopyrite metal terminated(112)surface((112)-M)is found in this work.First,through simulating the adsorption of an isolated water molecule and monolayer water molecules,it is confirmed that H_(2)O molecules tend to adsorb on the surface Fe atoms more than on the surface Cu atoms.Then,we studied various adsorption behaviors of the O_(2)molecule.It is found that the adsorption on the hollow FeAFe site is the most stable case;however,O_(2)is undissociated.Two adsorption cases will happen when H_(2)OAO_(2)adsorb simultaneously on the surface.For the S site,the H_(2)O molecule thoroughly dissociated and formed SAO species,and the other case is H_(2)O undissociated adsorbing at the Cu site.For the former case,it is interesting that H_(2)O is dissociated before O_(2).

DFT study on the interaction of HCHO molecule with S-doped TiO_(2) (001) surface without and with water and oxygen molecules

The interactions of formaldehyde(HCHO)molecule with S-doped anatase TiO_(2)(001)surface without and with water and oxygen were studied by density functional theory(DFT).The adsorption energy of HCHO adsorption on S-doped TiO_(2) surface with water and oxygen(-709.62 kJ/mol)is much larger than that without water and oxygen(-312.14 kJ/mol).For HCHO adsorption system without water and oxygen,one CeH bond of HCHO molecule is broken.The oxygen and carbon atoms of HCHO are bonded to the titanium and sulfur atoms of SeTiO_(2) surface,respectively,and form a CH_(2)OS structure.For the system with water and oxygen,H_(2)O and HCHO molecules are both dissociated.HCHO molecule not only interacts with TiO_(2) surface,but also combines with O_(2) molecule.Two CeH bonds of HCHO are broken,one hydrogen atom(H1)is bonded to the sulfur atom(S)of TiO_(2) surface doping,while another hydrogen atom(H_(2))is bonded to the O atom(O_(2))of O_(2) molecule.The remaining CeO bond can be oxidized to form CO_(2) in subsequent action by oxygen from the atmosphere.The surface doping of sulfur have significant impact on the degradation of HCHO molecule on anatase TiO_(2)(001)surface with H_(2)O and O_(2).

DFT study for combined influence of C-doping and external electric field on electronic structure and optical properties of TiO_(2)(001)surface

The electron structure and optical properties of C-TiO_(2)(001)surface under external electric field were studied by DFT method.After carbon doping,a new impurity level is introduced in the bandgap region of TiO_(2)(001)surface,and leads to the decrease of band gap,contributing to the shift of optical absorption to the visible region.When external electric field is applied across the C-TiO_(2)(001)surface,the band gap is further reduced with the increase of the electric field intensity from 0.1 eV to 0.5 eV.The electric field over 0.5 eV induces the electronic polarization.The spin-up bands show a gap,while spin-down electrons correspond to a metallic state.The energy gap of spin-up band decreases with increasing the electric field from 0.7 eV to 1.0 eV.The optical absorption of C-TiO_(2)(001)shifts to long wavelength compared with pure TiO_(2)(001).The electric filed make the optical absorption red-shift further,and the shift increases with an increase of the electric field,especially in the range of 0.7 eV-1.0 eV.The results show that the combined effect of carbon doping and electric field can enhance the photocatalytic activity of TiO_(2)(001)surface in visible region.