Rotating Disk Reactor Research Articles

Cu2O nanocrystals/TiO2 microspheres film on a rotating disk containing long-afterglow phosphor for enhanced round-the-clock photocatalysis

A Cu2O nanocrystals/TiO2 microspheres (Cu2O NCs/M-TiO2) rotating disk reactor assisted by long-afterglow phosphor was successfully designed and fabricated in order to achieve enhanced round-the-clock photocatalysis. The Cu2O NCs/M-TiO2 composite exhibited good photocatalytic activity owing to enlarged light absorption and efficient quantum yield by integrating Cu2O NCs with core-shell M-TiO2. Through rotating the catalyst disk, a thin aqueous film was formed on its upper part as well as continuously refreshed. Compared with bulk reaction, the photon propagation distance within this film was greatly shortened, and the possibility of light absorption by solution was correspondingly reduced, increasing the light utilization yield of photocatalytic system. Additionally, the continuous update of pollutants and their intermediates on catalyst was beneficial to photocatalysis. The long-afterglow phosphor in reactor could absorb excessive light energy and give out persistent fluorescence, exciting Cu2O NCs/M-TiO2 composite and realizing round-the-clock photocatalysis. As a result, the Cu2O NCs/M-TiO2 rotating disk reactor containing long-afterglow phosphor presented high reactivity in the photocatalytic degradation of rhodamine B and bisphenol A. The recycle experiments confirmed the stability and reliability of prepared reactor.

Effects of reaction-kinetic parameters on modeling reaction pathways in GaN MOVPE growth

In the modeling of the reaction-transport process in GaN MOVPE growth, the selections of kinetic parameters (activation energy Ea and pre-exponential factor A) for gas reactions are quite uncertain, which cause uncertainties in both gas reaction path and growth rate. In this study, numerical modeling of the reaction-transport process for GaN MOVPE growth in a vertical rotating disk reactor is conducted with varying kinetic parameters for main reaction paths. By comparisons of the molar concentrations of major Ga-containing species and the growth rates, the effects of kinetic parameters on gas reaction paths are determined. The results show that, depending on the values of the kinetic parameters, the gas reaction path may be dominated either by adduct/amide formation path, or by TMG pyrolysis path, or by both. Although the reaction path varies with different kinetic parameters, the predicted growth rates change only slightly because the total transport rate of Ga-containing species to the substrate changes slightly with reaction paths. This explains why previous authors using different chemical models predicted growth rates close to the experiment values. By varying the pre-exponential factor for the amide trimerization, it is found that the more trimers are formed, the lower the growth rates are than the experimental value, which indicates that trimers are poor growth precursors, because of thermal diffusion effect caused by high temperature gradient. The effective order for the contribution of major species to growth rate is found as: pyrolysis species>amides>trimers. The study also shows that radical reactions have little effect on gas reaction path because of the generation and depletion of H radicals in the chain reactions when NH2 is considered as the end species.

Effects of reaction-kinetic parameters on modeling reacting pathways in GaN MOVPE growth

In the modeling of the reaction-transport process in GaN MOVPE growth, the selections of kinetic parameters (activation energy E a and pre-exponential factor A ) for gas-phase reactions are very uncertain, which cause deviations in both chemical reaction path and growth rate. In this study, the deviations of kinetic parameters in the modeling of GaN MOVPE growth by previous researchers are summarized and the sources of the deviations are discussed. On this basis, numerical simulation of the reaction-transport process for GaN MOVPE growth in a vertical rotating disk reactor is carried out, with variation of the groups of kinetic parameters in different reactions, such as the pre-exponential factors in adduct formation and reversible dissociation, the pre-exponential factor and activation energy in irreversible adduct decomposition into amide, and the pre-exponential factor in the trimer formation. By comparisons of the molar concentrations of the major Ga-containing species and the corresponding growth rates, the effects of kinetic parameters on reaction paths in GaN MOVPE growth are determined. It is found that, for the adduct formation, if A is large ( A =2.18×1014 cm3 mol−1 s−1), adduct formation path will dominate followed by irreversible adduct decomposition to form amide; if A is small ( A =1.0×109 cm3 mol−1 s−1), the TMG pyrolysis will be the dominant path; if A is in mid-value ( A =1.0×1012 cm3 mol−1 s−1), both adduct formation path and TMG pyrolysis path will exist. For the reversible adduct dissociation, if A is large ( A =1.0×1014 s−1), growth rate will be higher and the pyrolysis path will dominate; if A is small ( A =9.5×109 s−1), both adduct formation path and TMG pyrolysis path will provide reaction precursors. For the irreversible adduct decomposition into amide, the activation energy E a will determine the reaction paths. If E a is small ( E a=32 kcal mol−1), the adduct formation path will dominate; if E a is large ( E a=49 kcal mol−1), both the adduct formation and the TMG pyrolysis exist. The main conclusions are obtained as follows: (1) different pre-exponential factors and activation energies lead to different reaction paths and growth rates, and the TMG pyrolysis path can increase the growth rate more effectively than the adduct formation path. (2) When the trimer formation is not considered, the predicted growth rates are close to the experimental value. The reason is that the transport-limited growth depends on the transport rate of Ga-containing species. Although the concentrations of Ga-containing species are different in different reaction paths, the total amount of Ga-containing species arriving on the substrate does not change much. The above fact gives well explanation why different previous researchers using different kinetic parameters for simulation obtained the similar growth rates with the experiment values. (3) When the trimer formation is considered and the pre-exponential factor for the trimer formation is varied, it is found that the trimer contribution to the growth rate is small due to the repulsive force on large molecules by thermophoretic force. The more the trimer is formed, the larger the growth rate error is. The simulation results have clarified some problems existed in the simulation of GaN MOVPE growth and improved the understanding for GaN growth reaction paths. The results of this study may not be applicable to the horizontal reactor, but it also has the guiding significance for the basic principle of the reaction-transport simulation.

Film formation in a horizontal twin-shaft rotating disk reactor for polymer devolatilization

Film formation characteristics in a horizontal twin-shaft rotating disk reactor for polymer devolatilization have been investigated by means of experiment and computational fluid dynamics (CFD). Volume of fluid (VOF) model has been used to simulate the film formation process and predict the film thickness distribution on the rotating disks, validated experimentally by electrical conductance method. The mechanism for the film formation in twin-shaft rotating disk reactor is different from that in single-shaft reactor, due to the effect of overlapping zone between two adjacent disks. There are two kinds of films generated in the reactor. The free film, greatly affected by the liquid viscosity and rotating speed, shows the similar characteristics with that in the single-shaft reactor. The scraped film, generated by overlapping zone, is much thinner and more uniform than the free film for highly viscous liquid. Compared with the viscosity and the rotating speed, the disk clearance plays a more significant role in determining the thickness and the shape of the scraped film.

A Photocatalytic Rotating Disc Reactor with TiO₂ Nanowire Arrays Deposited for Industrial Wastewater Treatment.

A photocatalytic rotating disc reactor (PRD-reactor) with TiO2 nanowire arrays deposited on a thin Ti plate is fabricated and tested for industrial wastewater treatment. Results indicate that the PRD-reactor shows excellent decolorization capability when tested with methyl orange (>97.5%). Advanced oxidation processes (AOP), including photocatalytic oxidation and photolytic reaction, occurred during the processing. Efficiency of the AOP increases with reduction in light absorption pathlength, which enhanced the photocatalytic reaction, as well as by increasing oxygen exposure of the wastewater thin film due to the rotating disc design. It is found that, with a small dosage of hydrogen peroxide, the mineralization efficiency of industrial biodegraded wastewater can be enhanced, with a superior mineralization of >75% total organic carbon (TOC) removal. This is due to the fact that the TiO2 photocatalysis and hydrogen peroxide processes generate powerful oxidants (hydroxyl radicals) that can strongly improve photocatalytic oxidation efficiency. Application of this industrial wastewater treatment system is benefited from the TiO2 nanowire arrays, which can be fabricated by a mild solvothermal method at 80 °C and under atmospheric pressure. Similar morphologies and microstructures are found for the TiO2 nanowire arrays deposited on a large metal Ti disc, which makes the wastewater treatment process more practical and economical.

Bacterial and fungal biofilm formation on anodized titanium alloys with fluorine.

Orthopaedic device-related infections are closely linked to biofilm formation on the surfaces of these devices. Several modified titanium (Ti-6Al-4V) surfaces doped with fluorine were studied in order to evaluate the influence of these modifications on biofilm formation by Gram-positive and Gram-negative bacteria as well as a yeast. The biofilm studies were performed according to the standard test method approved by ASTM (Designation: E2196-12) using the Rotating Disk Reactor. Four types of Ti-6Al-4V samples were tested; chemically polished (CP), two types of nanostructures containing fluorine, nanoporous (NP) and nanotubular (NT), and non-nanostructured fluorine containing samples (fluoride barrier layers, FBL). Different species of Gram-positive cocci, (Staphylococcus aureus and epidermidis), Gram-negative rods (Escherichia coli, Pseudomonas aeruginosa), and a yeast (Candida albicans) were studied. For one of the Gram-positive (S. epidermidis) and one of the Gram-negative (E. coli) species a statistically-significant decrease in biofilm accumulation for NP and NT samples was found when compared with the biofilm accumulation on CP samples. The results suggest an effect of the modified materials on the biofilm formation.

A simplified reaction model and numerical analysis for Si deposition from the SiHCl3-H2 system in vertical rotating disk reactors

The objectives of this study are to develop a simplified reaction model for Si deposition from an SiHCl3-H2 gas mixture, and to investigate the effect of the gas flow pattern on Si deposition in a vertical rotating-disk (VRD) reactor. A well-known simplified Si deposition model involves SiHCl3 adsorption and Si production by reaction with H2. On the other hand, it has been reported that the reactivity of HCl, which is a by-product from the SiHCl3-H2 system, has a strong influence on the Si deposition rate. Therefore, we have modified the simplified model to include this effect of HCl concentration. Numerical simulations of momentum, energy, and mass transport in the VRD reactor were conducted using the new reaction model. When the inlet gas flow rate was insufficient, the deposited Si films had non-uniform thickness in the radial direction of the wafer. The numerical results have indicated that large-scale recirculating flow occurs in the reactor, and the byproduct HCl gas accumulates in the reactor when the inlet gas flow rate is insufficient. Therefore, the film thickness is considered to decrease from the center to the perimeter of the wafer. The proposed simplified reaction model, which explicitly takes into account the effect of HCl, is able to predict such a distribution of the Si deposition rate on the wafer surface under conditions with insufficient flow rate.

Rotating Disk Apparatus: Types, Developments and Future Applications

Power consumption reduction investigations attracted the attention of enormous numbers of researchers in the past few decades due to its high academic and economic impacts. The pumping power losses during the transportation of crude oils are considered as one of the main power consuming applications due to the turbulent mode of transportation. Investigating the possible solutions for this problem is expensive and time consuming due to the large apparatuses needed to simulate the flow in real pipelines. Rotating disk apparatus (RDA) is an instrument mainly comprising a rotating disk and an electrical motor to rotate the disk, which was implemented as an efficient and economical path to simulate what can be done in pipelines through generating a controlled degree of turbulence. This technique was also used in many other scientific applications due to its dynamic mode of operation. For example, a rotating disk electrode was used in electrodeposition processes and to characterize deposition film thickness and uniformity. The rotating disk reactor was employed to investigate the reaction rate between fluids and solid surfaces. The present work evaluates the RDA from different prospective and applications in order to introduce it as an efficient research tools for future dynamic investigations.

Recovery of Copper from Effluents by Cementation on Aluminum in a Multirotating Cylinder-Agitated Vessel

Recovery of copper from synthetic waste solution using cementation technique in a new agitated vessel employing multirotating aluminum cylinders impeller was investigated. Parameters studied are cylinder diameter, rotation speed, initial copper ion concentrations, and effect of surfactants. Solution analysis and scanning electron microscopy were employed to investigate the kinetic and mechanism of the process. The rate of recovery was found to be at its maximum value at the operating conditions of 350 rpm rotation speed, 5000 ppm initial CuSO4 concentration, and 1.2 cm cylinder diameter. All data were correlated by the dimensionless equation: $$ {\text{Sh}} = 1.16 {\text{Sc}}^{0.33} {\text{Re}}^{0.63} \left( {\frac{{d_{\text{c}} }}{L}} \right)^{0.54}, $$ with an average deviation of ±8.5 pct and a standard deviation of 5.88 pct. Presence of nonylphenol ethoxylate surfactant in the solution decreased the rate of recovery by an amount ranging from 2.94 to 38.57 pct depending on the operating conditions. The present geometry gave higher rates of recovery compared to both the single rotating cylinder and rotating disc reactor.

A qualitative simulation of a face dissolution pattern in acidizing process using rotating disk apparatus for a carbonate gas reservoir

Formation damage caused by drilling, cementation, perforation, etc is a major problem facing oil and gas wells by reducing hydrocarbon production. Acidizing is an effective technique in carbonate reservoirs to reduce formation damages. Rotating disk reactor is an apparatus to measure reaction rate, reaction order, reaction rate constant, activation energy and diffusion coefficient. The author performed a core flood experiment with a dolomitic reservoir rock with hydrochloric acid and a face dissolution pattern is observed. In this study, the acidizing process is simulated with finite element codes and the flow pattern is observed qualitatively and the model is validated. In the simulation, model proposed by Panga is used. An optimum discretization method of the equations is employed in the simulation. In previous simulation studies, it was assumed that the reaction rate between mineral rocks with acid is first order therefore, linear model was constructed. In this study, by using a rotating disk reactor, it was shown that assumption of first order is not correct and non-linear model is constructed.

(Invited) Epitaxial III-Nitride Film Growth in a Single Wafer Rotating Disk MOCVD Reactor

Epitaxy of GaN on large-size Si wafers can enable the adoption of AlGaN-based High Electron Mobility Transistors (HEMTs) in a broad range of applications ranging from consumer electronics, solar and wind power, power supplies, and automotive, to the potential integration with Si-based CMOS technologies. Device performance dictates stringent requirements for epitaxial film quality and uniformity, while wafer bow management during growth facilitates the use of larger diameter substrates. Uniform temperature profile and gas distribution in the MOCVD reactor become critical elements for film performance and, ultimately, technology adoption. In this work, we are reporting on the epitaxy of Al/Ga/N containing films on 200 mm Si wafers. The TurbodiscÒ, vertical, rotating disk reactor used for epitaxy encompasses the fundamental reaction and high velocity laminar flow characteristics of its predecessor batch systems, thus enabling stable, repeatable operation, long PM cycles, and direct, model-based process scale up. Moreover, it incorporates advanced features, which will be discussed, for alkyl/hydride flow distribution and temperature uniformity, which translate into excellent uniformity in epitaxial layer thickness, alloy composition, and doping profile across the wafer. Results on AlGaN/GaN heterostructures, thickness uniformity of GaN 0.48%, 1σ, and AlN 0.86%, 1σ, Al composition uniformity in AlGaN of 0.289%, 1σ, and 2DEG performance are presented. Uniform incorporation of dopant species (Mg and C) across the substrates is reported. The average Hall mobility is > 1700 cm2/V.s, with sheet carrier concentration at 9.5x1012/cm2, and sheet resistance 380 Ohm/sq for the 5 points across the wafer. Results on the repeatability of film quality, FWHM of GaN (002) and (102) showing < 1.5% 1σ over 20 runs, and average Al composition of AlGaN barrier, showing variation of 0.37 % 1σ over 16 runs, are presented. Wafer bow can be precisely engineered and controlled through the thickness and composition of the stress compliance structure.

Optimization of Gallium Nitride Metalorganic Chemical Vapor Deposition Process

This paper investigates the simulation, response surface modeling, and optimization of the metalorganic chemical vapor deposition (MOCVD) process for the deposition of gallium nitride (GaN). Trimethylgallium (TMGa) and ammonia (NH3) are the precursors carried by hydrogen into the rotating-disk reactor. The deposition rate of GaN film and its uniformity form the focus of this study. Computational fluid dynamics (CFD) model simulates the deposition of the GaN film. CFD model is employed to identify two design variables, inlet velocity and inlet precursor concentration ratio, which significantly affect the deposition rate and uniformity of GaN film. Compromise response surface method (CRSM) is used to generate response surfaces for average deposition rate and uniformity. These response surfaces are used to generate the Pareto front for the conflicting objectives of optimal rate of average deposition and uniformity. Pareto front captures the trade-off between deposition rate and uniformity of the GaN film. It is observed that for the whole range of design variables, there are numerous options to get stable uniformity levels than deposition rate. The optimal inlet velocity and precursor concentration for different objective functions considered tend to be near the upper bounds.

Fabrication of Gallium Nitride Films in a Chemical Vapor Deposition Reactor

A numerical study has been carried out on the metalorganic chemical vapor deposition (MOCVD) process for the fabrication of gallium nitride (GaN) thin films, which range from a few nanometers to micrometers in thickness. The numerical study is also coupled with an experimental study on the flow and thermal transport processes in the system. Of particular interest in this study is the dependence of the growth rate of GaN and of the uniformity of the film on the flow, resulting from the choice of various design and operating parameters involved in the MOCVD process. Based on an impingement type rotating-disk reactor, three-dimensional simulations have been preformed to indicate the deposition rate increases with reactor pressure, inlet velocity, and wafer rotating speed, while decreases with the precursor concentration ratio. Additionally, a better film uniformity is caused by reducing the reactor pressure, inlet velocity and wafer rotating speed, and increasing precursor concentration ratio. With the impact of wafer temperature included in this study as well, these results are expected to provide a quantitative basis for the prediction, design, and optimization of the process for the fabrication of GaN devices. The flow and the associated transport processes are discussed in detail on the basis of the results obtained to suggest approaches to improve the uniformity of thin film, minimize fluid loss, and reduce flow recirculation that could affect growth rate and uniformity.

Residual structure of Streptococcus mutans biofilm following complete disinfection favors secondary bacterial adhesion and biofilm re-development.

Chemical disinfection of oral biofilms often leaves biofilm structures intact. This study aimed to examine whether the residual structure promotes secondary bacterial adhesion. Streptococcus mutans biofilms generated on resin-composite disks in a rotating disc reactor were disinfected completely with 70% isopropyl alcohol, and were again cultured in the same reactor after resupplying with the same bacterial solution. Specimens were subjected to fluorescence confocal laser scanning microscopy, viable cell counts and PCR-Invader assay in order to observe and quantify secondarily adhered cells. Fluorescence microscopic analysis, particularly after longitudinal cryosectioning, demonstrated stratified patterns of viable cells on the disinfected biofilm structure. Viable cell counts of test specimens were significantly higher than those of controls, and increased according to the amount of residual structure and culture period. Linear regression analysis exhibited a high correlation between viable and total cell counts. It was concluded that disinfected biofilm structures favored secondary bacterial adhesion.

Novel wedge structured rotating disk photocatalytic reactor for post-treatment of actual textile wastewater

A wedge structured rotating disk photocatalytic (PC) reactor was used for post-treatment of actual textile wastewater collected after activated sludge treatment. Compared with a conventional planar disk, the wedge structured disk had larger surface area and exhibited better light utilization efficiency. Treatment conditions such as pH and rotating speed were optimized. The COD content in effluent was reduced from 380mgO2L−1 to 109 and 56mgO2L−1 respectively after 3h and 5h treatment at pH 6.0 and rotating speed of 20rpm. The effect of anions (NO3−, SO42− and Cl−) in actual textile wastewater on treatment was investigated. Benefit from high light utilization efficiency, the wedge rotating disk reactor could compensate COD removal inhibition caused by anions. A 1.5V voltage was also applied to perform photoelectrocatalysis process to further improve the performance, and no additional electrolyte was needed. COD in effluent was reduced to as low as 75mgO2L−1 after 3h treatment. In addition, this reactor was used to treat other water samples including the actual textile wastewaters collected before activated sludge treatment (initial COD of 880mgO2L−1) and after activated carbon adsorption post-treatment (initial COD of 108mgO2L−1). Experimental results suggested that wedge structured rotating disk photocatalysis process was stable, efficient and worth further scale-up investigation.

BiOBr visible-light photocatalytic films in a rotating disk reactor for the degradation of organics

BiOBr visible-light photocatalytic films utilized in a rotating disk reactor have achieved improved photoactivity for the degradation of color organics.

Water quality variation and tubing metal release due to nitrification

Metals are released during nitrification in drinking water distribution systems; therefore, the release of metal due to nitrification and the relationship between pipe material and water quality variation have been investigated in this research by rotating disk reactors (RDRs). As a result, the extent of nitrification depended on the pipe material; nitrifiers grown on metal surfaces would be unfavorable relative to inert surfaces because of metal toxicity. Results implicate that nitrification could affect water quality and metal release. In RDR with Cu coupons, copper release was accompanied by a decrease in pH and an increase in the nitrite concentration resulting from nitrification. Fe and Zn ions from galvanized steel followed a pattern similar to that of Cu coupons. Stainless steel was identified as the material that was the least influenced by nitrification. As for other metal ions, metal coupons generally released more metal ion when nitrification existed, moreover, it released more metal than plastic pipe whether nitrification exists or not. Electrochemical reactions and acidic environments that result from nitrification may induce these differences. Surprisingly, iron and manganese released from steel material were found to be highly correlated (R = 0.9373), and iron-to-manganese ratio precisely conform to their composition.

Mathematical model of decolourization in a rotating disc reactor

This work presents a mathematical model of the biodegradation of an organic dye in a rotating disc reactor operated in a batch mode with discs coated with a mycelium of a white-rot fungus. The two-dimensional model domain represents the surface of one half of a disc. The disc is considered to be covered with two layers (biofilm, liquid film) and is partially immersed in bulk liquid. The biofilm is assumed to maintain a constant thickness in time over the entire domain. The enzyme laccase is presumed to play the main role in the decolourization. The regular disc rotation is described using the radial coordinate with the immersion process simulated by a step-like function of the angular coordinate.Using experimental data, we identified values of principal model parameters. Considering the Michaelis–Menten constant value of 0.005kgm−3, we found suboptimal values of the reaction rate constant (0.003molm−3s−1), proportionality constant influencing the thickness of the liquid film in the submerged phase (7×10−6mrad0.5s−0.5) and dye diffusion coefficient in the liquid phase (8×10−10m2s−1). Subsequent parametric studies suggested that the model was able to predict both qualitative and quantitative characteristics of the experimental rotating disc bioreactor on various time scales.

Enzymatic cleaning of biofouled thin-film composite reverse osmosis (RO) membrane operated in a biofilm membrane reactor

Application of environmentally friendly enzymes to remove thin-film composite (TFC) reverse osmosis (RO) membrane biofoulants without changing the physico-chemical properties of the RO surface is a challenging and new concept. Eight enzymes from Novozyme A/S were tested using a commercially available biofouling-resistant TFC polyamide RO membrane (BW30, FilmTech Corporation, Dow Chemical Co.) without filtration in a rotating disk reactor system operated for 58 days. At the end of the operation, the accumulated biofoulants on the TFC RO surfaces were treated with the three best enzymes, Subtilisin protease and lipase; dextranase; and polygalacturonase (PG) based enzymes, at neutral pH (~7) and doses of 50, 100, and 150 ppm. Contact times were 18 and 36 h. Live/dead staining, epifluorescence microscopy measurements, and 5 μm thick cryo-sections of enzyme and physically treated biofouled membranes revealed that Subtilisin protease- and lipase-based enzymes at 100 ppm and 18 h contact time were optimal for removing most of the cells and proteins from the RO surface. Culturable cells inside the biofilm declined by more than five logs even at the lower dose (50 ppm) and shorter incubation period (18 h). Subtilisin protease- and lipase-based enzyme cleaning at 100 ppm and for 18 h contact time restored the hydrophobicity of the TFC RO surface to its virgin condition while physical cleaning alone resulted in a 50° increase in hydrophobicity. Moreover, at this optimum working condition, the Subtilisin protease- and lipase-based enzyme treatment of biofouled RO surface also restored the surface roughness measured with atomic force microscopy and the mass percentage of the chemical compositions on the TFC surface estimated with X-ray photoelectron spectroscopy to its virgin condition. This novel study will encourage the further development and application of enzymes to remove biofoulants on the RO surface without changing its surface properties.

Ionic-liquid-assisted growth of flower-like TiO2 film on Ti substrate with high photocatalytic activity

Flower-like anatase TiO2 films on Ti substrate were prepared via direct oxidation in H2O2 solution assisted with [Bmim]BF4 ionic liquid. The promotion effect of ionic liquid to both the growth of anatase TiO2 crystal and the formation of flower-like morphology was demonstrated. The formation process of flower-like TiO2 film was investigated via adjusting the oxidation reaction time. During the photo-degradation of aqueous rhodamine B solution under UV light (λ=365nm) in rotating disk reactor, the obtained flower-like TiO2 film exhibited efficient decomposition of rhodamine B, which could be contributed that the flower-like morphology of TiO2 film with high anatase crystallization and mesoporous structure led to the enhancement of light harvesting and reactant adsorption. Furthermore, the excellent stability of TiO2 film during the photo-degradation reaction was resulted from the stable combination of TiO2 film with Ti substrate.