TiO2 Lattice Research Articles

Extraction of W, V, and As from spent SCR catalyst by alkali pressure leaching and the pressure leaching mechanism

Spent selective catalytic reduction (SCR) catalysts are environmentally hazardous and resource-enriching. In this work, V, W, and As in a spent SCR catalyst was extracted by alkali pressure leaching. Results showed that the V, W, and As were loaded on the anatase TiO2 crystal grains as amorphous oxides. The optimum pressure leaching conditions were NaOH concentration of 20 wt%, reaction temperature of 180 °C, reaction time of 120 min, L/S of 10 mL/g, and stirring speed of 300 rpm. The leaching efficiency of W, V, and As reached 98.83%, 100%, and 100%, respectively. The experiment revealed the preferential leaching of V and As rather than W, and the leaching mechanisms of V, W, and As were studied through experiment and density functional theory (DFT). The leaching kinetics of W conformed to a variant of the shrinking core model and the leaching process of W is controlled by both chemical reactions and diffusion processes. During the leaching process, Na2Ti2O4(OH)2 product powder layer was generated, which affects the mass transfer of W. The destruction of the TiO2 skeleton in the spent SCR catalyst is essential for adequate W extraction, especially for the extraction of W embedded in the TiO2 lattice. The DFT simulation result indicated that the V and As loaded onto the TiO2 support are easier to absorb hydroxide ions rather than W, and the leaching reaction energy of V and As was lower than W, As, and V has leaching priority over the leaching of W. Furthermore, an anatase TiO2 photocatalyst with the {001} crystal surface exposed was successfully prepared from the alkali pressure leaching residue. This work provides theoretical support for the metal leaching and utilization of spent SCR catalysts via alkali pressure leaching.

Control of metal oxides’ electronic conductivity through visual intercalation chemical reactions

Cation intercalation is an effective method to optimize the electronic structures of metal oxides, but tuning intercalation structure and conductivity by manipulating ion movement is difficult. Here, we report a visual topochemical synthesis strategy to control intercalation pathways and structures and realize the rapid synthesis of flexible conductive metal oxide films in one minute at room temperature. Using flexible TiO2 nanofiber films as the prototype, we design three charge-driven models to intercalate preset Li+-ions into the TiO2 lattice slowly (µm/s), rapidly (mm/s), or ultrafast (cm/s). The Li+-intercalation causes real-time color changes of the TiO2 films from white to blue and then black, corresponding to the structures of LixTiO2 and LixTiO2-δ, and the enhanced conductivity from 0 to 1 and 40 S/m. This work realizes large-scale and rapid synthesis of flexible TiO2 nanofiber films with tunable conductivity and is expected to extend the synthesis to other conductive metal oxide films.

Tailoring the photocatalytic properties of anatase TiO2 by B–TM (TM = Pt, Ta, V) co-doping

In order to provide insight into the influence of co-doping with boron (B) and transition metals (TM = Pt, Ta, V) on the photoactivity of anatase TiO2, the electronic, structural and optical characteristics of the mentioned co-doped systems were studied using density functional theory calculations and the modified Becke–Johnson exchange potential. For each transition metal two cases were considered, with B atom either replacing O atom (B-substitutional) or imbedding interstitially (B-interstitial) into TiO2 lattice. The calculations showed that the co-doping is more favorable for the B-interstitial systems than for the B-substitutional ones and under the O-rich conditions. For the B-substitutional cases a slight decrease of the band gap is observed. In contrast, the results obtained for the B-interstitial systems exhibited no band gap narrowing. However, in these systems, the occurrence of localized states within the band gap is noticed, which could improve visible light absorption through a two-step optical transition.

The Role of Lattice Defects on the Optical Properties of TiO2 Nanotube Arrays for Synergistic Water Splitting.

In this study, we report a facile one-step chemical method to synthesize reduced titanium dioxide (TiO2) nanotube arrays (NTAs) with point defects. Treatment with NaBH4 introduces oxygen vacancies (OVs) in the TiO2 lattice. Chemical analysis and optical studies indicate that the OV density can be significantly increased by changing reduction time treatment, leading to higher optical transmission of the TiO2 NTAs and retarded carrier recombination in the photoelectrochemical process. A cathodoluminescence (CL) study of reduced TiO2 (TiO2-x) NTAs revealed that OVs contribute significantly to the emission bands in the visible range. It was found that the TiO2 NTAs reduced for a longer duration exhibited a higher concentration of OVs. A typical CL spectrum of TiO2 was deconvoluted to four Gaussian components, assigned to F, F+, and Ti3+ centers. X-ray photoelectron spectroscopy measurements were used to support the change in the surface chemical bonding and electronic valence band position in TiO2. Electron paramagnetic resonance spectra confirmed the presence of OVs in the TiO2-x sample. The prepared TiO2-x NTAs show an enhanced photocurrent for water splitting due to pronounced light absorption in the visible region, enhanced electrical conductivity, and improved charge transportation.

Reasonable design of Sm-modified Cu-based catalyst for NH3-SCO: Role of the amide intermediates

The selective catalytic oxidation of ammonia (NH3-SCO) is currently the most effective method used to eliminate NH3. However, one of the major challenges for NH3-SCO is the development of catalyst capable of completely converting NH3 into harmless N2 and water vapor. In this paper, a high N2 selective catalyst prepared by the sol-gel method using TiO2 as the support, Cu as the active species, and Sm as the auxiliary agent is presented. Compared to traditional Cu/TiO2 catalyst, the 4SmCu/TiO2 catalyst has higher catalytic activity and N2 selectivity at low temperatures. The NH3 conversion can reach 100%, and the selectivity of N2 can be maintained at 100% at 275 °C. The excellent catalytic activity is attributed to the highly dispersed active species, abundant Lewis acid sites (LASs), and the generation of large amounts of surface-adsorbed oxygen. In addition, doping Sm species will cause TiO2 lattice distortion, and at the same time load the distorted TiO2 with more active material. Moreover, in-situ DRIFTS analysis suggests that both the 4SmCu/TiO2 and Cu/TiO2 catalysts follow the "internal" selective catalytic reduction (iSCR) mechanism during NH3-SCO reactions. The 4SmCu/TiO2 catalyst generates more amides (-NH2), which reduces the non-selective oxidation of the catalysts and promotes the formation of N2. This provides a new idea and method for the selective catalytic oxidation of NH3 to N2 and water vapor using Cu-based catalysts.

Improvement of Photocatalytic Degradation of Titanium Dioxide Nanomaterials by Non-metal Doping

Semiconductor photocatalysis is a process that benefits from sunlight to start chemical reactions. In order to take advantage photocatalytic properties of semiconductors and to achieve better performance structural adjustment is needed. In this study, varying amounts of nitrogen were used to modify TiO2 nanostructures using the sol-gel method. The crystalline structure of the synthesized TiO2 nanostructures was studied using the X-ray diffraction (XRD) technique. X-ray photoelectron spectroscopy (XPS) was conducted to analyse the elemental composition of nanomaterials. XPS analyze confirms that nitrogen is introduced into the lattice of TiO2. The photocatalytic degradation of methylene blue (MB) under UV irradiation was employed to assess the photocatalytic performance of the samples. To evaluate degradation, the absorption of MB over time was measured using a UV-Vis spectrophotometer. As a result, the doping process has been found to improve the photocatalytic performance of TiO2, and 0.2% N doped TiO2 nanostructures demonstrated superior photocatalytic activity for photocatalytic degradation of MB.

Optimal Deposition of a Thin FeOOH Layer on S-TiO2/BiSbS3 p-n Junction for Improved Solar Water Splitting and Mechanistic Insights

Hydrogen is gaining significant attention as a clean fuel option due to its high energy density, which can be produced through solar water splitting. In this study, S-TiO2 photocatalyst has been synthesized using the sol-gel method. Analysis revealed that cation substitution S+4 and S+6 of Ti+4 in the TiO2 lattice resulted in the formation of S=O bond and S-Ti-O bond. The S-TiO2 was then coated with BiSbS3 using the chemical bath deposition (CBD) method, followed by the deposition of FeOOH using the similar technique. The resulting photoelectrode, S-TiO2/BiSbS3/FeOOH, exhibited a photocurrent density of 4.36 mA.cm−2 at 1.23 V vs reverse hydrogen electrode and a solar-to-hydrogen efficiency of 1.31% at 0.6 V vs RHE, outperforming other electrodes. The improved photoactivity was attributed to the synergetic effect of heterojunction and cocatalyst loading. This study provides insight into the potential applications of cocatalysts in (photoelectrochemical) PEC water splitting.

Structural, optical and magnetic studies of sol-gel synthesized Mg-doped pure anatase TiO2 nanoparticles for spintronic and optoelectronics applications

Here in we reported the synthesis of MgxT1−xO2 (for x = 0.00, 0.01, 0.02, 0.03, 0.04) nanoparticles via simple sol-gel technique. Mg-doped TiO2 is a hopeful material for the study of the origin of room-temperature ferromagnetism (RTFM) in dilute magnetic semiconductors (DMS) systems, but very scanty work on this material has been reported. The as-synthesized samples were subjected to X-ray diffraction (XRD) which shows that the samples aligned with tetragonal anatase phase of TiO2. UV\\Vis\\NIR diffuse reflectance spectroscopy analysis showed a slight increase in TiO2 energy band gap with Mg doping from 3.25eV to 3.33 eV as a result of blue shift in absorbance edge of the sample. The obtained recombination of photo-generated electrons and holes is excellently curbed by Mg doping which was examined by the photoluminescence study and the blue shift in the most intense Eg (3) Raman mode confirms integrated Mg in TiO2 lattice. As revealed by Field Emission Scanning Electron Microscopy (FESEM), the morphology of the samples showed irregularly distributed nanoparticles and to examine elemental composition of the samples, Energy Dispersive X-ray (EDX) were carried out which stipulates all elements like Ti and Mg are in the sample. Soft ferromagnetism at low magnetic field with hysteresis loop was noticed in all the samples, with values of coercivity in the range 206–309Oe. Maximum value of saturation magnetization was evident by the 2% doped sample. These materials can find applications in electronics, spintronics and magneto-optics devices.

Structural and optical properties of sol-gel synthesized TiO2 nanocrystals: Effect of Ni and Cr (co)doping

Nickel and chromium metal ions have been utilized to dope and co-dope titanium dioxide nanocrystals, thereby broadening the light absorption range of titania into the visible light spectrum. The doped and co-doped TiO2 nanocrystals were prepared using sol-gel techniques, with a varied doping concentration that extended from 0.25 to 10.0 wt%.These modified materials underwent comprehensive analysis using standard analytical tools such as X-ray diffraction, Raman spectroscopy, BET surface area measurement, Fourier transform infrared spectroscopy, UV–vis diffuse reflectance spectroscopy, and fluorescence spectroscopy. Powder XRD technique reveals that the modified catalyst majorly contains the anatase polymorph with the transition metal ion either substituting Ti or located as interstitials in the lattice of TiO2. Raman and UV–Vis absorption spectra of the doped and codoped catalyst a show λmax shift towards longer wavelength when in the metal ion concentration is increased from 0.25 to 10 wt%. FTIR patterns show the stretching and vibration patterns of hydroxyl radicals present in the nanocrystals. The BET surface areas of the doped and codoped TiO2 nanocrystals have substantially higher surface areas compared with that of the undoped TiO2. Electronic structural studies of the TiO2, (Ti,Cr)O2, (Ti,Ni)O2, and (Ti,Ni,Cr)O2 crystals using density functional theory indicated a reduction in the band gap width (Eg) of pure TiO2 when doped with transition metals. Specifically, the indirect bandgap values for Ni(10%), Cr(10%) and NiCr(5% + 5%) doping were 2.96, 2.83, and 2.7 eV, respectively. Furthermore, the photoluminescence intensity substantially decreased with the incorporation of transition metal ions in the TiO2 nanocrystals.

Enhanced humidity sensing properties of interstitial B-doped TiO2 nanofibers

This paper investigates the ability of boron (B) as a dopant in TiO2 nanofibers for use in humidity sensing. B-doped TiO2 nanofibers are synthesized through tuning molar ratio of B/Ti using a facile electrospinning technique. The influences of B content on the phase transition, specific surface area, morphology, and surface valence of TiO2 nanofibers are studied by employing XRD, BET, SEM, and XPS characterization tests. The doping mode and humidity sensing performances for B doping TiO2 nanofibers are also performed in detail. The results show that B is successfully incorporated into the TiO2 lattice using interstitial mode, inducing the increase in cell volume and specific surface area, decreasing grain size. Compared to pristine TiO2 nanofibers, interstitial B doping generates oxygen vacancies and increases the Ti3+ concentration, resulting in an increase in humidity sensitivity. The B-doped TiO2 nanofibers based on the optimum B/Ti molar ratios of 1:4 exhibit high sensitivity, excellent linearity, narrow hysteresis, quick response and recovery time as well as favorable repeatability and stability, which are promising humidity sensing materials. The sensing mechanism is systematically investigated using electrochemical impedance spectroscopy combined with equivalent circuits.

Ca2+ doped TiO2 nano-sized polygon plates with oxygen vacancies for photocatalytic hydrogen evolution

Photocatalytic hydrogen evolution using suitable photocatalysts in water is a sustainable way of energy production. In this paper, Ca2+ doped TiO2 nano-sized polygon plates with oxygen vacancies were synthesized. The incorporation of Ca2+ induces the loss of oxygen and the formation of oxygen vacancies in the TiO2 lattice, confirmed by XPS and EPR. TiO2 with 0.040% Ca adding amount shows the best photocatalytic hydrogen production activity (4485 μmol g−1 h−1) with the apparent quantum efficiency of 46.4% at 370 nm, higher than undoped TiO2 (2182 μmol g−1 h−1). The successful incorporation of Ca2+ and the formation of oxygen vacancies effectively inhibit the recombination of carriers in the reaction process and enhance the photocatalytic hydrogen production activity.

Improved photocatalytic decolorization of reactive black 5 dye through synthesis of graphene quantum dots-nitrogen-doped TiO2.

Graphene quantum dots (GQDs), a new solid-state electron transfer material was anchored to nitrogen-doped TiO2 via sol gel method. The introduction of GQDs effectively extended light absorption of TiO2 from UV to visible region. GQD-N-TiO2 demonstrated lower PL intensity at excitation wavelengths of 320 to 450nm confirming enhanced exciton lifespan. GQD-N-TiO2-300 revealed higher surface area (191.91m2g-1), pore diameter (1.94nm), TEM particle size distribution (4.88 ± 1.26nm) with lattice spacing of 0.45nm and bandgap (2.91eV). In addition, GQDs incorporation shifted XPS spectrum of Ti 2p to lower binding energy level (458.36eV), while substitution of oxygen sites in TiO2 lattice by carbon were confirmed through deconvolution of C 1s spectrum. Photocatalytic reaction followed the pseudo first order reaction and continuous reductions in apparent rate constant (Kapp) with incremental increase in RB5 concentration. Langmuir-Hinshelwood model showed surface reaction rate constants KC = 1.95mg L-1min-1 and KLH = 0.76 L mg-1. The active species trapping, and mechanism studies indicated the photocatalytic decolorization of RB5 through GQD-N-TiO2 was governed by type II heterojunction. Overall, the photodecolorization reactions were triggered by the formation of holes and reactive oxygen species. The presence of •OH, 1O2, and O2• during the photocatalytic process were confirmed through EPR analysis. The excellent photocatalytic decolorization of the synthesized nanocomposite against RB5 can be ascribed to the presence of GQDs in the TiO2 lattice that acted as excellent electron transporter and photosensitizer. This study provides a basis for using nonmetal, abundant, and benign materials like graphene quantum dots to enhance the TiO2 photocatalytic efficiency, opening new possibilities for environmental applications.

Ti-Mo-O Nanotube Arrays Grown by Anodization of Magnetron Sputtered Films

In this study, we introduced the method for the growth of titanium molybdenum oxide (TMO) nanotubes directly from metallic precursor solid state solution and provided their structural and chemical characterization. Precursor films with content of molybdenum from 32 to 82 at% were prepared using co-deposition magnetron sputtering. The optimization of deposition parameters allowed for the growth of a continuous nanotube array with a length up to 700 nm ± 10% by anodic oxidation. Scanning electron microscopy (SEM) combined with energy-dispersive spectroscopy (EDS) revealed nanotube formation with Ti1−xMoxO2 composition, where x can reach the value of 0.5. Scanning transmission electron microscopy combined with EDS (STEM-EDS) confirmed the incorporation of Mo into the TiO2 lattice and uniform elemental distribution across the nanotube at the submicron level. The nanobeam electron diffraction (NBD) and X-ray diffraction analyses (XRD) did not show any notable crystal phase formation for the titanium molybdenum oxide phase.

Comparative study of TiO2–Fe3O4 photocatalysts synthesized by conventional and microwave methods for metronidazole removal

This study focused on a direct comparison of conventional hydrothermal and microwave treatment during the synthesis of TiO2–Fe3O4 photocatalyst, which is an effective catalyst for decomposing metronidazole. The photocatalyst underwent various characterization analyses, including X-ray diffraction, Raman spectroscopy, transmission electron microscopy, energy dispersive X-ray, and diffuse reflectance spectroscopy. The Raman spectroscopy analysis revealed that the materials obtained through the conventional hydrothermal treatment consisted of separate phases of anatase and magnetite. On the other hand, the materials synthesized using the microwave process showed a noticeable shift in the Eg band (143 cm−1) and its half-width towards higher wavenumbers. This shift is likely due to the introduction of Fe ions into the TiO2 lattice. Additionally, both conventional hydrothermal and microwave synthesis routes produced TiO2–Fe3O4 systems with superparamagnetic properties, as demonstrated by SQUID magnetic measurements. The TEM analysis revealed that the materials synthesized using the microwave process exhibited higher homogeneity, with no noticeable large aggregates observed. Finally, this work proposed a convenient LED photoreactor that effectively utilized the photo-oxidative properties of TiO2–Fe3O4 photocatalysts to remove metronidazole. Combining photoactive TiO2–Fe3O4 catalysts with an energy-efficient LED reactor resulted in a low electrical energy per order (EEO).

Enhanced electron extraction using neodymium ions doped TiO2 for all-inorganic CsPbBr3 perovskite solar cells

The high-quality electron-transport layer (ETL) plays a vital role in boosting the power conversion efficient (PCE) of perovskite solar cells (PSCs). Herein, the lanthanide neodymium (Nd) is used as a dopant to incorporate into the lattice of TiO2 to reduce the trap states and form a n-doping effect, resulting in an increase in electron mobility and conductivity of TiO2, an energy level of TiO2 matching well with that of the perovskite layer. Moreover, the improved wettability of the Nd-TiO2 film enables a fabrication of perovskite light-absorbing layer with high-quality. As a result, the all-inorganic CsPbBr3 PSCs based on Nd-TiO2 ETL achieve a champion PCE of 10.06% owing to the promotion of charge extraction and the inhibition of charge recombination, which is a significantly improved efficiency in comparison with the 6.57% value of the reference cell. Additionally, the target device without encapsulation displays an effectively enhanced stability with over 90% and 80% retention of the original efficiency after aging in ambient air with high humidity (80% RH, 25 °C) for 30 days and under AM 1.5 G illumination at 85 °C for 100 h, respectively.

Mg doped TiO2 thin films: Optical, dielectric, photocatalytic, magnetic and antibacterial studies

The sol-gel dip-coating route was utilized to synthesize Mg-doped TiO2 thin films with Mg doping concentration (2,4,6,8 and 10) wt.%. The prepared films were transparent, homogeneous, and compact. The development of the anatase phase was confirmed by the diffraction peaks of XRD spectra. The size of crystallites was observed to be reduced from 12.08 to 11.82 nm when the dopant concentration was increased. The dielectric behavior of all thin films was standard. The AC conductivity was used to investigate the barrier height, the density of localized states at the Fermi level, and the hopping distance. Ferromagnetism was observed for Mg-doped TiO2 thin films. The antibacterial activity of Mg-doped TiO2 was optimal and can be applied in nanomedicines. According to the findings, Mg replaced Ti in the TiO2 lattice and produced new energy levels, lowering the bandgap of the doped films. Furthermore, increasing the Mg content caused the optical absorption of the films to shift from the ultraviolet to the visible range. The research indicated that doping a little amount of Mg into TiO2 thin film can increase visible light absorption, making it a promising material for use in solar cells to capture solar radiation. Mg-doped TiO2 exhibited favourable photocatalytic activity for the degradation of methylene blue at a concentration of 10 wt% Mg. Methylene blue was degraded in the presence of sunlight, making it a promising material for water treatment and environmental pollution. Mg-doped TiO2 thin films can also be used as CO gas sensors.

Enhanced immobilization of Arsenic(III) and Auto-oxidation to Arsenic(V) by titanium oxide (TiO2), due to Single-Atom vacancies and oxyanion formation

Pollution control of As(III), a naturally occurring carcinogen, has recently gained a global attention, while due to the dominance of neutral H3AsO3 over a wide pH range, As(III) immobilization by most minerals is not efficient as As(V) immobilization. TiO2 shows promise for controlling As(III) pollution, and herein, a comprehensive study about As(III) adsorption by TiO2 and oxyanion formation is conducted by means of DFT + D3 methods. Both anatase and rutile are effective for As(III) adsorption, while As(III) adsorption affinities differ significantly and are −1.48 and −3.79 eV for pristine surfaces, ascend to −3.85 and −5.08 eV for O vacancies, and further to −5.37 and −5.26 eV for Ti vacancies, respectively. The bidentate binuclear complexes dominate for pristine surfaces, and O vacancies prefer OAs insertion into TiO2 lattice, while for Ti vacancies, all As(III) centers are auto-oxidized to As(V). Ti-3d, O-2p or/and As-4p rather than other orbitals contribute significantly to As adsorption, and O and Ti vacancies promote adsorption through stronger orbital hybridization. The superior adsorption for Ti vacancies originates from As(V) formation instead of bonding interactions. The formation of As oxyanions, which may occur spontaneously at pristine surfaces and is greatly promoted by O and Ti vacancies, enhances As(III) adsorption pronouncedly and becomes a viable strategy for As(III) immobilization. H2AsO3- and HAsO32- dominate for pristine surfaces and O vacancies, and for Ti vacancies, H2AsO4- and HAsO42- dominate over anatase whereas AsO43- also makes an important contribution over rutile. Results rationalize experimental observations available, and provide significantly new insights about the migration, bioavailability and fate of As(III) over TiO2 surfaces that facilitate the exploration of scavengers for As and other pollutants.

Preparation and Photoelectrochemical Properties of Mo/N Co-Doped TiO2 Nanotube Array Films

Mo/N co-doped TiO2 nanotube array films were obtained by a combination of magnetron sputtering and anodization. The influences of doping concentration and nanotube morphology on the structure, morphology, elemental composition, light-absorption capacity, and optoelectronic properties of TiO2 nanotubes were studied. The findings revealed that Mo was primarily incorporated into the TiO2 lattice in the Mo6+ valence state, while N was mainly embedded into the lattice as interstitial atoms. It was observed that when the sputtering power was 35 W for TiN target and 150 W for Mo-Ti target, the Mo/N co-doped TiO2 nanotube array films exhibited the best photovoltaic performance with a photogenerated current of 0.50 µA/cm2, which was 5.5 times of that of Mo-doped TiO2. The enhanced photocatalytic efficiency observed in Mo/N co-doped TiO2 nanotube array films can be ascribed to three main factors: an increase in the concentration of photogenerated electrons and holes, a reduction in the band gap width, and intense light absorption within the visible spectrum.

Influence of support properties on selective oxidation of 2-methylnaphthalene on vanadia-molybdena based catalyst

In this work, the catalytic performance of vanadia-molybdena loaded on TiO2, MgO, ZSM-5, NaY and Mordenite was investigated in the selective oxidation of 2-methylnaphthalene (2-MN) to 2-naphthaldehyde (2-NA). Results show that strong interactions between supports (TiO2, ZSM-5) and active components can promote the dispersion of active component. Monolayer VOx and MoOx are the main form on the catalyst surface, which is beneficial to the 2-NA selectivity. However, the corresponding weak interactions between Mordenite and active components may lead to the production of oxide crystals and the separation of active components, thus reducing the 2-NA selectivity. Due to the high Na content, new crystal NaVMoO6 forms on the NaY surface, which is inactive in the reaction. For V-Mo/TiO2, V and Mo can be inserted into the TiO2 lattice, changing the electronic structures of active components and support and improving the activity of surface oxygen species. This investigation highlights an important consideration on supports properties when designing supported catalysts.

Study on preparation and properties of nanocrystalline TiO2/graphite photocatalytic composite by mechanochemistry

Graphite-modified TiO2 composite is a promising photocatalyst in environmental purification. In this study, TiO2/graphite photocatalytic composites were prepared by mechanochemistry using natural flake graphite and nanocrystalline TiO2 as raw materials. The composites were examined by X-ray diffractometer, Raman spectrometer, X-ray photoelectron spectrometer, scanning electron microscope and UV-vis spectrophotometer. The photoelectrochemical properties of the composites were investigated via electrochemical impedance spectroscopy and photocurrent response. The influences of the content and premilling time of graphite on the photocatalytic properties of the composites were studied through the photocatalytic decomposition of methylene blue. The results showed that graphite was exfoliated and broken during ball milling, and defects of graphite increased with the extension of milling time. In the composite, there is no solid solution of carbon atoms in TiO2 lattice. The photocatalytic results indicated that a proper amount of graphite could improve the photocatalytic behavior of TiO2. The TiO2/graphite composite containing 1wt% graphite exhibited the best photocatalytic behavior. The pretreatment of graphite by ball milling could enhance the photocatalytic behavior of the TiO2/graphite composite and the optimal premilling time of graphite was 4 hours.