Study On Preparation And Performance Of New AgI/Am-TiO₂-O And Ta/Al-Fe₂O₃Photocatalysts

It is of great scientific value and profound realistic significance to use semiconductor which can efficiently use and convert solar energy into chemical energy for pollutants treatment. The key point is to develop the stable and efficient photocatalysts which can utilize the visible light.A novel visible light driven photocatalyst, AgI/Am-TiO2-O, was synthesized by onestep deposition-precipitation method. The as-prepared photocatalyst was a mixture of β-AgI and y-AgI supported on amorphous TiO2. Under visible light irradiation, AgI/Am-TiO2-O-N showed greater photocurrent and stronger electrocatalytic ability for oxidation than AgI/P25-TiO2, AgI/An-TiO2and AgI/Am-TiO2.AgI/Am-TiO2-O-N represented highest catalytic activity and superior stability on degradation of Org Ⅱ and RhB. The optimal activity for the degradation of Org Ⅱ was achieved at slightly acidic to neutral pH (5.2), proper catalyst dosage (2g/L), and higher light intensity (89.9mW/cm2). The dominating reactive species involved in Org Ⅱ degradation process were O2·-and h+.AgI/Am-TiO2-O-N and AgI/P25-TiO2were used for the visible light induced synergistic removal of dye (RhB) and Cr(Ⅵ). The influence of pH value was also investigated. It was found AgI/Am-TiO2-O-N exbihited more significant synergistic effect than AgI/P25-TiO2when RhB coexisted with Cr(VI). For AgI/Am-TiO2-O-N, RhB and Cr(VI) could be cooperatively degradated within a wide pH value ranged from3to10, indicating AgI/Am-TiO2-O-N was highly desirable for the remediation of RhB and Cr(VI) co-contaminated wasterwaters. Morever, lower pH value was beneficial to increase the oxidation of RhB and reduction of Cr(VI).A new type of tantalum and aluminum co-doped iron oxide (Ta/Al-Fe2O3) photoanode was also fabricated by a simple drop coating method. Ta/Al-Fe2O3film presented excellent enhanced photoelectrocatalytic (PEC) activity and photostability, a15times higher photocurrent density as well as two times higher incident-photon-to-current efficiency (IPCE) can be observed relative to Al-Fe2O3under visible light irradiation. Results from surface characterization and PEC experiments indicated that Ta and Al were successfully co-doped into Fe2O3and Ta could greatly influence the chemical environment of Al and O on the catalyst surface. The dramatic enhanced PEC performance were attributed to mixed effects induced by tantalum doping, such as positive shift of flat band potential, a reduction in anodic overpotential for water oxidation and greatly reduced charge transfer resistance, which eventually facilitated more efficient separation and easier transfer of photogenerated electron-hole pairs.PEC, electrocatalytic (EC) and photocatalytic (PC) degradation of MB were carried out using Ta/Al-Fe2O3electrode as the photoanode. The influencing factors such as pH value, applied voltage were investigated. Results indicated that the PEC process had synergetic effects in enhancing the discoloration efficiency of MB in comparison with the individual PC or EC process. MB discoloration efficiency of Ta/Al-Fe2O3was2times higher under visible light irradiation than that of Al-Fe2O3. The acidic solutions were favorable for the PEC degradation of MB. The PEC reaction rate of MB increased with the enhancement of the applied voltage in a certain range. Possible mechanism for the degradation of MB was proposed:Ta/Al-Fe2O3 could generate electron and hole under irradiation and excite photoelectrons from the valance band to conduction band. Then the electrons were scavenged by O2to yield O2-and H2O2in oxygen-equilibrated media. Those new formed intermediates could interact to produce OH. It is well known that-OH and holes were powerful oxidizing agents capable of degrading MB into CO2and H2O.