Interfacial Charge Interactional Transfer Promotes Photocatalytic Phenol Mineralization

Heterogeneous photocatalytic oxidation has a bright application prospect in the degradation of low concentration phenolic wastewater,but the lack of hydroxyl radical generation and the slow interfacial charge transfer process hinder the practical application of this technology.Efficient photocatalytic degradation requires simultaneous promotion of photoinduced hydroxyl radical generation and semiconductor-cocatalyst interfacial charge transfer（SC）,while the inherent correlation of photoinduced hole extraction to electronic Fermi level allow us to promote photocatalytic contaminant mineralization by facilitating the transfer of electrons from semiconductor to the solution.In this paper,Ti O₂,the most widely used photocatalyst,was selected as the main photocatalyst to improve the photocatalytic activity of the catalyst from the aspects of accelerating hole extraction and promoting electron transfer,and to explore the internal logic of interfacial charge correlation transfer.（1）In order to improve the photocatalytic mineralization performance,solvothermal method was used to synthesize Cu-Ti O₂,and characterization methods such as SEM,TEM,XRD and so on proved that Cu entered the Ti O₂ lattice in the form of bulk doping,and doping almost did not change the band position and light absorption of Ti O₂.LSV experiment proved that modified Ti O₂ was more close to water oxidation potential(E_H2O/·OH=2.4 V vs RHE),which was conducive to the generation of hydroxyl radical.The photocatalytic mineralization performance is close to that of the phenol wastewater without relying on the noble metal co-catalyst Pt,and the COD value of phenol wastewater decreases below 20 after 2 hours photocatalytic mineralization.（2）We here develop a fixed bed photocatalyst based on homogeneous contact that can facilitate reduction half-reaction by simultaneously promoting semiconductor-cocatalyst interfacial electron transfer and the collision of dissolved oxygen to the catalytic sites.Besides,this photocatalyst configuration can alleviate competitive light absorption by the contaminant and cocatalyst.Importantly,the efficient electron transfer can synergistically promotion the hydroxyl radical generation for mineralizing recalcitrant contaminants like phenol in the wastewater.It is proved by photoelectric chemistry that there is a strong internal correlation between hole transfer and Fermi level of electron.When electrons accumulate in the semiconductor,Fermi level increases,the probability of hole-electron recombination is high,and the hole transfer rate is slow.Ti O₂|Cu-Ti O₂ reduce photoinduced potential,accelerate the electron transfer,Forward movement of photoinduced potential can reduce the electron concentration in the semiconductor.Since the product of electron concentration and hole concentration can be approximated to a constant,the dawnshfit of the Fermi level can increase the number of holes in the semiconductor,facilitating the photoinduced of·OH.After 2 hours of degradation,Ti O₂|Cu-Ti O₂ can completely mineralized phenol in the wastewater,transcend the traditional cocatalyst system（Pt-TiO₂）.