Preparation Of TiO₂-NiTiO₃ Composite Film By In-situ Microwave Anodization And Its Photocatalytic Performance

With the development of world economy,the problem of water pollution is becoming increasingly serious,and thus it is urgent to control water pollution.Traditional physical and chemical methods for water pollution can only treat the symptoms but not cure the root causes.This problem could be solved by semiconductor catalysts such as: ZnO,CdS,WO 3,etc.,Among them,TiO2 has become the most commonly used and reliable catalyst material in practical applications due to its advantages of good photocatalytic activity,environmental friendly and harmless,cheap and easy to get,stable properties et al..However,TiO2 shows obvious shortcomings of the wide band gap width of about 3.0 e V,leading to its only absorption of ultraviolet light(about 4% of the total solar energy)in the sunlight,and extremely low sunlight utilization.Compared with TiO2,NiTiO3(NTO),a narrower band gap width(approximately 2.18 eV),can absorb visible light(about 45% of total solar energy)in the sunlight,and also exhibits excellent photoelectric conversion capability.But,its high photo-generated electron-hole pair recombination rate limit its further application.In this case,a composite thin film of TiO2-NiTiO3 was synthesized by an in-situ microwave anodization to address the photocatalytic performance of TiO2.The effections of deposition time,deposition voltage,and external bias voltage on the degradation properties of the thin film material were systematically studied.The main contents are as follows:A thin film of TiO2-NTO composite was in the first time successfully prepared by a microwave-assisted in-situ anodization method.Of them,most of TiO2 forms a heterostructure with NTO,resulting in the band gap of TiO2 changed from 3.0 e V to 2.49 e V,which can thereof absorb visible light.The effects of deposition time on the degradation performance of the composite thin film were studied.In the conditions of a deposition voltage of 25 V,a applied bias of 1.4 V,and visible light source,with the increase of deposition time,the efficiency of photocatalytic degradation of methylene blue increased first and then decreased.60 min is an optimal depositing time for photocatalytic degradation of methylene blue(MB)using the composite film,and the degradation efficiency of methylene blue(MB)was 82.4% at 120 min.The effects of deposition voltage on the degradation properties of composite film materials were systematically studied.In the conditions of a deposition time of 60 min,an applied bias of 1.4 V,and exposed simulated sunlight,As the deposition voltage increased,the efficiency of the composite thin-film photocatalytic methylene blue increased first and then decreased.The composite film prepared at a deposition voltage of 25 V had the best degradation efficiency of methylene blue(MB),arriving at 93.76% at a degradation efficiency of 120 min.The effects of the applied bias voltage on the degradation properties of composite film materials were systematically studied.In the conditions of a deposition voltage of 25 V,a deposition time of 60 min and simulated sunlight exposure,with the increase of the applied bias,the degradation increased first and then decreased slightly.The composite film material showed the best degradation efficiency of methylene blue(MB)under 2.2 V external bias voltage,reaching 99.65% at 120 min.For the composite film prepared at a deposition time of 60 min and a deposition voltage of 25 V,an external bias voltage of 1.4 V was used to perform a cyc le stability test under simulated sunlight.After five cycles,the degradation performance of the composite film decreased from 93.76% to 92.12%,a decrease of 1.64%,indicating that the composite material possesses good stability.