Effect Of Surface Impurities On Anatase TiO₂?101?surface Adsorption Of Sp³ Hybrid Gas Molecules

Titanium dioxide has been its non-toxic,stable chemical properties,photo catalytic ability,cheap and easy preparation and other excellent characteristics attract the attention of many scholars,but also play an important role in solving the problem of energy utilization and environmental governance issues etc.However,due to its wide band gap,TiO₂ can only respond in the ultraviolet region,the utilization rate of visible light is very low,and the photocatalytic activity of TiO₂ is relatively low.It is important to study the microscopic properties of TiO₂ doped impurity ions or surface adsorbed gas molecules,which can improve the photocatalytic activity and provide theoretical basis for the experimental study.This paper use the first-principles plane-wave ultrasoft pseudopotential method based on density functional theory?DFT?to construct Cu-C,N,F doped and Co doped anatase phase TiO₂ model and simulate.The results showed Cu-N co-doping system and Cu,N single-doped system are better than other systems in the use of visible light.The reason is that the Cu and N elements respectively acceptor level cooperative action result in the Cu-N codoped system response to visible light effect is the best.The second step,we construct N-Sc,V,Cr,Mn,Fe codoped anatase TiO₂ structure model and simulate calculation.The results show the order of each doped system visible light absorption capacity is N-Fe > N-Cr > N-Mn > N-Sc > N-V > N.The results verification that the double acceptor level is beneficial to the optical excitation,also found4 s atomic orbit of Cr is not completely filled,which hybridized with p electronic orbit is most likely to act as photo-generated electron trap centers,and result in that the photo-catalytic activity of N-Cr co-doped Ti O2 is higher than that of N-Mn co-doped TiO₂.The third step is to study the microscopic mechanism of NH₃ and H2 O adsorption on anatase TiO₂?101?surface.After the NH₃ molecules adsorption on the surface of oxygen vacancies,a new energy level appeared near the Fermi surface,which changed the response ability of anatase Ti O2?101?to visible light.This provides a theoretical basis for the material as an optical gas sensing material.Finally,the characteristics and mechanism of NH₃ adsorption on B,C,N,F doped TiO₂?101?surface were studied.The results show that the adsorption effect of NH₃ on the doped surface is better than that of the undoped surface.The surface doped C is the most stable adsorption structure by comparison with different elements doping.The analysis of Mulliken charge distribution and difference charge density show: near the Fermi surface,the greater contribution of the doping atoms to the electronic density of states,the smaller the charge transfer net value of doped atoms and NH₃ molecule,the smaller adsorption distance,the greater the adsorption energy,and the adsorption structure is more stable.