Theoretical Calculation Study On The Adsorption Strengthening Mechanism Of O₃ Molecules On The TiO₂ Interface By Applying Positive Electric Field

Electro-heterogeneous catalytic ozonation（E-catazone）is a novel advanced oxidation technology developed by our group in the early stage,which achieves a highly efficient synergy between electrochemistry and ozone（O₃）-TiO_2-NFheterogeneous catalytic reaction by applying an positive electric field to a porous titanium aeration anode loaded with TiO₂nanoflowers(TiO_2-NF).Electrochemical and ozone（O₃）-TiO_2-NFheterogeneous catalytic reactions are efficiently synergized.Previous studies have demonstrated that for ozone-inert pharmaceutical micro-pollutants（PMP）(ibuprofen k _O3=9.6 M^-1s^-1,p-chlorobenzoic acid k _O3<0.1M^-1s^-1,etc.),E-catazone can increase the pollutant removal rate by 50～70 times and hydroxyl radical yield by two orders of magnitude compared to ozone catalysis and electrochemical oxidation alone,and it has been preliminarily demonstrated that The enhanced effect of applied positive electric field on the adsorption and conversion of O₃molecules at the Ti/TiO₂interface and the generation of reactive oxygen species（ROS）has been demonstrated.However,the mechanism of the enhanced effect of the applied positive electric field on the adsorption of O₃at the Ti/TiO₂interface,which is a key prerequisite for this enhanced effect,is still unclear and needs to be studied.Therefore,based on density functional theory（DFT）,this thesis investigates the effect of applied positive electric field on the adsorption of O₃molecules at Ti/TiO₂interface,focusing on the effect of applied positive electric field on the adsorption energy of Ti/TiO₂interface,identifying the key adsorption sites and adsorption modes.TiO₂crystalline surface and crystalline type;finally,the mechanism of the enhanced effect of the applied positive electric field on the adsorption of O₃at the Ti/TiO₂interface was elucidated by the charge density and density of states analysis.The following key conclusions are mainly drawn.（1）The enhanced adsorption effect of the applied positive electric field（0.2 V/（?）～1 V/（?））on O₃molecules at the Ti/TiO₂interface was confirmed.At an applied positive electric field of 1 V/（?）,the adsorption energy(E_ads)of O₃molecules at the Ti/TiO₂interface was enhanced by 29%～125%on the Ti-based anatase TiO₂（101）crystal plane（Ti/TiO₂（A101））compared to that without the applied positive electric field.（2）The key sites（double H₂O molecules）and adsorption modes（bridging adsorption）for the adsorption of O₃molecules at the Ti/TiO₂interface were clarified using the Ti/TiO₂（A101）crystalline surface as an example.By systematically studying different adsorption sites(single H₂O molecule,double H₂O molecules,single hydroxyl（OH）,double hydroxyl（2OH）,H₂O-OH,Ti⁴⁺Lewis acid sites,etc.)and different adsorption modes（bridging adsorption,single-arm adsorption）,it was found that with the bridging adsorption mode of double H₂O molecules,O₃molecules are more easily adsorbed at the Ti/TiO₂interface and have more stable adsorption structures,and the obtained adsorption energy(E_ads)was-4.16 e V,which was much higher than those obtained at other sites（-0.87 e V～-3.04 e V）.（3）It is further confirmed that the applied positive electric field also has O₃adsorption enhancement on different crystalline Ti/TiO₂（A001）and different crystalline types（titania-based rutile TiO₂110 crystalline surface,Ti/TiO₂（R110））.The maximum enhancement of O₃molecule adsorption energy at Ti/TiO₂（A001）and Ti/TiO₂（R110）interfaces by the applied positive electric field ranges from（15%～31%）compared to Ti/TiO₂（A101）crystalline surface.（4）After the analysis of charge density and density of states,the above enhanced adsorption effect is mainly caused by the charge redistribution inside Ti/TiO₂caused by the applied positive electric field,which promotes the migration of H-atom electron clouds from H₂O molecules to O-atoms in O₃molecules at the interface and the overlapping hybridization of orbitals,and the degree of overlapping has a positive correlation with the electric field strength.As shown above,this thesis has elucidated the strengthening mechanism of the applied positive electric field on the adsorption reaction between O₃molecules and TiO₂molecules at the atomic level:the applied positive electric field promotes the charge density,electron transfer and overlapping hybridization of orbitals between O₃and H atoms of H₂O molecules at the interface,which in turn reduces the distance between O₃molecules and H₂O molecules at the interface and increases the adsorption energy of Ti/TiO₂-O₃.The elucidation of the above enhancement mechanism can provide basic data for the electrochemical precise regulation of ozone heterogeneous catalysis and conversion pathways,and provide the fundamental principles for the subsequent real-time regulation of catalyst interfacial properties and ROS generation in engineering.It is worth noting that the applied positive electric field studied in this paper is smaller than the decomposition electric field of H₂O molecules（1.23 V/（?））,which belongs to the non-Faraday reaction interval,and the application of the above weak electric field can realize the efficient enhancement of ozone interfacial catalysis,which provides a new idea for the development of low consumption and green water treatment technology.