N-doped TiO2 Nanoparticles Research Articles

One step synthesis of N-doped and Au-loaded TiO2 nanoparticles by laser pyrolysis: Application in photocatalysis

Photocatalysis is a major tool for air and water depollution and photocatalysts with improved efficiency in the visible range are still needed. In this context, we show that N-TiO2 nanoparticles modified with Au, called Au/N-TiO2, seem to represent a good compromise: significant photocatalytic activity is observed under visible light together with an activity higher than TiO2 P25 under UV irradiation. In order to demonstrate such efficiency of the Au/N-TiO2 sample, TiO2, Au-TiO2, N-TiO2 and Au modified N-TiO2 nanoparticles were synthesized in one step using the laser pyrolysis method. The photocatalytic activity of the powders was evaluated through the photocatalytic degradation of formic acid (FA) both under UV and visible light irradiation. Under UV irradiation, all the laser-synthesized samples exhibit a high efficiency compared to commercial TiO2 P25. Moreover, the modification by Au induces an enhancement of the photocatalytic activity compared to pure TiO2 even at very low concentrations. Under visible light, the N-doped samples exhibit some photoactivity and the degradation rate of FA in presence of Au/N-TiO2 is much increased compared to N-TiO2. In conclusion, our Au/N-TiO2 sample exhibits efficiency better than P25 under UV together with an activity under visible light.

Density functional theory study of the adsorption of NO2 molecule on Nitrogen-doped TiO2 anatase nanoparticles

Adsorption of NO2 molecule on pristine and N-doped TiO2 anatase nanoparticles have been studied using the density functional theory (DFT) technique. The structural properties (such as bond lengths and bond angles) and the electronic properties (such as density of states, band structures and atomic partial charges) have been computed for considered nanoparticles. The results show that, the adsorption of NO2 molecule on N-doped nanoparticles is more energetically favorable than the adsorption of NO2 molecule on the pure TiO2 nanoparticles. However, on the base of the obtained results, the N-doped TiO2 nanoparticles can be used in NO2 sensing and removing applications.

Photocatalytic removal of atrazine using N-doped TiO2 supported on phosphors

Visible light-active N-doped TiO2 (N-TiO2) was successfully immobilized on ZnS-based phosphors microparticles (ZSP) by a modified sol–gel method. Core-shell catalysts were prepared to serve as “photoactive support”, able to harvest the external irradiation and to emit a luminescence with wavelength suitable for activation of N-doped TiO2. The nominal loading of N-TiO2 on ZSP was in the range of 15–50wt% and the effect of the progressive increase in N-TiO2 loading on the coverage of phosphors particles was evaluated. The preparation method did not induce alterations of the initial ZSP crystallographic structure and allowed to obtain N-TiO2 dispersion on ZSP surface. By varying the N-TiO2 loadings on the surface of ZSP, its morphology gradually evolved from pseudo-spherical shape, until 30wt% N-TiO2 loading, to elongated shape for an N-TiO2 content of 50wt%. The photocatalytic activity of N-TiO2/ZSP was evaluated for the removal of atrazine under UVA light irradiation. Enhanced performance compared to either pure N-TiO2 nanoparticles or bare ZSP was observed. The photocatalyst N-TiO2/ZSP at 30wt% of N-TiO2 loading (30N-TiO2/ZSP) demonstrated the highest photocatalytic activity. Photocatalytic performances were strongly dependent on the concentration of catalyst and the initial pH of solution. The optimal catalyst concentration was 0.5gL−1 and the optimal initial pH was 5.8. A study of the reaction intermediates during the photocatalytic removal of atrazine was carried out, evidencing that the sequence of intermediates for 30N-TiO2/ZSP and for the phosphors ZSP alone included dealkylation reactions and alkyl chain oxidation.

Preparation of N doped TiO2 via microwave-assisted method and its photocatalytic activity for degradation of Malathion

We report herein, nitrogen doped TiO2 nanostructure synthesized by simple microwave assisted method, where ammonia was used as hydrolyzing agent. The synthesized nanomaterials were characterized by means of X-ray diffraction (XRD) which demonstrated that N-doped TiO2 is in anatase phase with average crystallite size of 10nm. Doping of N into the lattice of TiO2 was supported by X-ray photoelectron spectroscopy (XPS), Fourier transform-infrared spectroscopy (FT-IR), CHNS analysis, energy dispersive spectroscopy (EDS). The diffuse reflectance spectroscopy (DRS) showed shifting of absorption edge toward the visible region. Thermogravimetric–differential thermal analysis (TGA–DTA) points out N-doped TiO2 nanoparticles are thermally stable. In order to achieve maximum degradation efficiency, the effect of catalyst loading, pH and light sources (UV and sunlight) were studied. A maximum 97% degradation efficiency was achieved under optimized conditions. A 80% reduction in the chemical oxygen demand (COD) was observed after 150min that indicated mineralization of Malathion. The cytotoxicological studies indicate that photocatalytically degraded products were less toxic as compared to Malathion.

Synthesis of N-doped TiO2 photocatalyst for low-concentration elemental mercury removal under various gas conditions

This study proposes preparing N-doped TiO2 nanoparticles that exhibit a narrow bandgap by calcinating a mixture of Degussa P-25 TiO2 and NH4Cl at a temperature of 400°C under airtight conditions to remove gaseous elemental mercury (Hg0). Sample characterization performed using X-ray photoelectron spectroscopy and ultraviolet-visible spectra indicated that the presence of Ti3+ caused by oxygen vacancy and molecular-state N may be incorporated into a TiO2 lattice; this result was supported by an observation of the Ti–N group conducted using Fourier transform infrared spectroscopy. The formed nanoparticles exhibited a size of 32.4nm and were in a mixed form of anatase and rutile according to the X-ray diffraction spectra. The low Hg removal of TiO2 nanoparticles under the 0% O2 dark condition indicated that photocatalytic oxidation limited Hg adsorption. The reemission of adsorbed Hg caused by H2O competition for active sites can be markedly inhibited by N modification, which may be caused by strong bonding between Hg, N, and O groups. In addition, TiOxNy underwent less adsorption competition from humidity at an elevated temperature than an untreated sample did. NO exhibited substantial competition for the adsorption sites on the TiO2 surface. By contrast, under dark conditions, both SO2 and HCl slightly enhanced Hg adsorption; under ultraviolet and visible-light irradiation, both SO2 and HCl markedly reduced Hg removal. SO2 and HCl may substantially consume O2− and OH free radicals during light irradiation and subsequently reduce the transformation of Hg0 into HgO.

Photocatalytic effects of wool fibers modified with solely TiO2 nanoparticles and N-doped TiO2 nanoparticles by using hydrothermal method

The surfaces of wool fibers are modified with N-doped TiO2 nanoparticles by treating the fibers with tetrabutyl titanate and ammonium chloride under low temperature hydrothermal conditions to obtain wool fibers with photocatalytic functions in the visible light spectrum. The effects of nitrogen and sulfur in amino acids in keratin on the photocatalytic activity of TiO2 particle coated wool fibers are investigated. Changes of various fiber properties such as tensile strength, photocatalytic activity, and self-cleaning performance of untreated, TiO2 coated and N-doped TiO2 coated wool fibers are studied. It is found that N-doped anatase TiO2 nanoparticles with an average grain size of 11.2 nm are synthesized and simultaneously grafted onto the wool fibers. After treatments, the crystallization index of the wool fibers is slightly reduced. The capability to protect against ultraviolet radiation is much enhanced. The performances of photocatalytic degradation of methylene blue dye and self-cleaning of red wine under both UV and visible light irradiation are endowed. It is also found that wool fibers coated with TiO2 particles without being doped by nitrogen still have apparent photocatalytic reactions and self-cleaning effects under visible light irradiation due to the formation of C-Ti3+, O-Ti3+, and N-Ti3+ bonds between TiO2 and wool keratin on the wool fiber surfaces. Thus wool fabrics might not need to be coated with N-doped TiO2 nanoparticles to realize its self-cleaning effect under visible light. Such important conclusions would provide wool materials with wide applications in clothing and technical products such as wastewater treatment.

Electro-catalytic activity of palladium modified nitrogen doped titania nanoparticles.

Pd-modified N-doped TiO2 nanoparticles were prepared by the sol-gel method. The X-ray diffraction (XRD) pattern indicated that the pure anatase TiO2 has been obtained. Transmission electron microscope (TEM) was used to observe the micro-morphology of the nanoparticles. The average size of the particles was 8.04 nm. The N2 adsorption isotherm of the resulted nanoparticles was the type IV with a H1 type hysteresis loop. The specific surface area was 145.2 m2 g(-1) and the average diameter of adsorption was 4.178 nm. These Pd-modified N-doped TiO2 nanoparticles were applied onto the surface of glass carbon electrode (GCE), and its electro-catalytic activity was tested by cyclic voltammetry (CV). The reduction peak currents showed a linear response to the dissolved oxygen (DO) concentrations ranging from 0.6 mg L(-1) to 7.2 mg L(-1) on the Pd-N-TiO2/ GCE. The linear regression equation was y = 3E - 6x + 1E-5 (R = 0.9909). The detection limit was 0.22 mg L(-1.) The result indicated that the Pd-N-TiO2 possessed a good electro-catalytic activity.

Effect of calcination on the visible light photocatalytic activity of N-doped TiO2 prepared by the sol-gel method.

A series of N-doped TiO2 nanoparticle powders have been prepared by the sol-gel method using triethylamine as N precursor. The effect of calcination temperatures on the quality of the as-prepared samples was studied and an annealing treatment was introduced to improve further the quality of the as-prepared sample. The visible light photocatalytic activities of the samples were evaluated by decomposition of methyl orange (MO) in water. The calcination temperature plays a key role in determining the quality of N-doped TiO2 nanoparticle powders. The enhancement of calcination temperatures facilitates the crystallization of N-doped TiO2 powders and the elimination of surface organic residues, but promotes the loss of doping N and the agglomeration of nanoparticles and results in low N doping level and large particle sizes. The N-doped TiO2 sample (NT-300) calcined at 300 degrees C in air for 3 h produced the maximum visible light photocatalytic activity. The annealing treatment of NT-300 at its calcination temperature could improve the crystallinity, remove effectively the surface organic residues, keep nanoparticles in smaller size, and retain the doping N, therefore improving the visible light photocatalytic activity significantly.

Modification of dye-sensitized solar cell working electrode using TiO2 nanoparticle/N-doped TiO2 nanofiber composites

Nanocomposite films of N-doped TiO2 nanofibers (NFs) and commercial-grade TiO2 nanoparticles Degussa (P25) were utilized as working electrode of typical dye-sensitized solar cells (DSSCs). N-doped TiO2 NFs were fabricated via electrospinning method using ammonium acetate (CH3COONH4) as nitrogen source and titanium (IV) isopropoxide (TiP) in ethanol as starting precursor in combination with calcinations process. The electrospun NFs were characterized by XRD, Raman spectroscopy, XPS, SEM, and TEM. The photoelectric conversion performance of the DSSCs with composite film electrode was compared to the device using pure P25 film. The result shows that as calcination temperature increases, the anatase-to-rutile phase transformation and the fiber size reduction of NFs were observed. The energy conversion efficiency (η) of the device tends to increase with increasing calcined temperature with specific nanofiber loading content, indicating the significant enhancement in the device performance by the incorporation of the NFs. This enhancement of DSSCs may attribute to high surface area, higher light scattering and light harvesting, low charge recombination, and fast electron-transfer rate by loaded NFs.

Improvements in the Electrochemical Kinetic Properties and Rate Capability of Anatase Titanium Dioxide Nanoparticles by Nitrogen Doping

Pure anatase TiO2 and N-doped TiO2 nanoparticles were prepared by a solvothermal method. X-ray photoelectron spectroscopy showed that the surface of the doped material was dominated by interstitial N, while interstitial and substitutional N coexisted in the material bulk. Both materials showed superior cycle stability. In addition, the N-doped material exhibited much better rate capability than pure TiO2. A discharge capacity of 45 mAh g(-1) was obtained at the 15 C rate, which was 80% higher than that of pure TiO2. The electrochemical kinetic properties of the materials were studied by a galvanostatic intermittent titration technique and electrochemical impedance spectroscopy. The charge-transfer resistance of TiO2 was decreased by N doping. Meanwhile, the minimum lithium diffusion coefficient was increased to 2.14 × 10(-11) cm(2) s(-1), which is 13 times higher than that of pure TiO2. This indicates that the electrochemical kinetic properties of TiO2 were improved by N doping, which substantially improved the specific capacity and rate capability of TiO2.

Characterization of N-doped TiO2 nanoparticles supported on SrTiO3 via a sol–gel process

A heterojunction photocatalyst that efficiently enhanced hydrogen production from an aqueous solution containing a sacrificial reagent under solar irradiation was developed by growing N-doped TiO2 on SrTiO3 via a sol–gel process. The effect of N-doped TiO2 combined with SrTiO3 on the heterojunction properties was studied. The heterojunction characterization results indicated that the coupling of SrTiO3 with N-doped TiO2 enhanced the visible-light-absorption range because N-doped TiO2 acted as photosensitizer. In addition, N-doped TiO2 coated on SrTiO3 prevented particle agglomeration, providing the heterojunction materials with finer crystals of anatase TiO2 and larger specific surface area than the theoretical values. However, when the SrTiO3/N-doped TiO2 weight ratios were increased to over 10 %, the material increasingly showed SrTiO3-like properties, which gradually decreased the solar-energy-absorption efficiencies, SBET values,, and photoactivity. At the 5 % weight ratio of SrTiO3/N-doped TiO2, the photocatalytic H2 production rates of the heterojunction were significantly increased by up to 94.2 %, which could be ascribed to the efficient electron/hole separation, charge migration from the photocatalyst interior to the surface, absorption range of visible light, and prevention of particle agglomeration.

Solvothermal synthesis of N-doped TiO2 nanoparticles using different nitrogen sources, and their photocatalytic activity for degradation of benzene

Anatase-brookite mixed-phase N-doped TiO2 (N-TiO2) nanoparticles were synthesized through a solvothermal method using different nitrogen sources. The resulting samples were characterized by X-ray diffraction, specific surface area measurement, X-ray photoelectron spectroscopy, and standard and high-resolution transmission electron microscopy. The effects of the different nitrogen sources on phase composition, particle size, microstructure, and specific surface area are investigated. The photocatalytic activity of the TiO2 samples was evaluated through photocatalytic degradation of gaseous benzene under UV-light irradiation. N-TiO2 prepared using hydrazine hydrate achieved the highest photocatalytic performance in all the samples studied (including the commercial P25). Different intermediates during the photocatalytic degradation of benzene over HNT were identified by GC-MS analysis. A detailed reaction mechanism was proposed to explain their formation as intermediates in the reaction. Moreover, the photocatalytic activity of the nanoparticles remained almost unchanged after 15 gaseous-benzene degradation test cycles.

One-step solvothermal synthesis of N-doped TiO2 nanoparticles with high photocatalytic activity in the reduction of aqueous Cr(VI)

N-doped TiO2 (N-TiO2) nanoparticles were synthesized via a one-step low temperature (180 °C) solvothermal route, which adopted NH4NO3 as the nitrogen source. The structure, composition, BET specific surface area, and optical properties of the as-synthesized product were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, N2 adsorption–desorption isotherms, and UV–vis diffuse reflectance spectroscopy. In addition, its photocatalytic properties were tested by the reduction of aqueous Cr(VI) under UV and visible light (x > 420 nm) irradiation. It was observed that for the reduction of aqueous Cr(VI), the as-synthesized N-TiO2 nanoparticles not only exhibited much higher photocatalytic activity than P25 TiO2 under UV light, but also exhibited remarkably high photocatalytic activity under visible light (λ > 420 nm).

Magnetic resonance study of annealed and rinsed N-doped TiO2 nanoparticles

Abstract Nanoparticles of nitrogen-modified TiO2 (N-doped TiO2) calcined at 300°C and 350°C, have been prepared with and without water rinsing. Samples were characterized by x-ray diffractrometry (XRD) and optical spectroscopy. The electron paramagnetic resonance (EPR) spectra from centers involving oxygen vacancies were recorded for all samples. These could be attributed to paramagnetic surface centers of the hole type, for example to paramagnetic oxygen radicals O−, O2−etc. The concentration of these centers increased after water rising and it further increased for samples annealed at higher temperature. Additionally, for samples calcined at 300°C, and calcined at 350°C and rinsed, the EPR spectra evidenced the presence of magnetic clusters of Ti3+ ions. The photocatalytic activity of samples was studied towards phenol decomposition under unltraviolet-visible (UV-Vis) irradiation. It was found that, in comparison to the starting materials, the rinsed materials showed increased photocatalytic activity towards phenol oxidation. The light absorption (UV-Vis/DRS) as well as surface Fourier transform infrared/diffuse reflectance spectroscopy (FTIR/DR) studies confirmed a significantly enhanced light absorption and the presence of nitrogen groups on the photocatalysts surfaces, respectively. A significant increase of concentration of paramagnetic centers connected with oxygen vacancies after water rising has had an essential influence on increasing their photocatalytic activity.

Combined embedding of N-doping and CaCO3 surface modification in the TiO2 photoelectrodes for dye-sensitized solar cells

A successive embedding of N-doping and CaCO3 surface modification was carried out in the TiO2 photoelectrodes for dye-sensitized solar cells (DSSCs). The combined effect was revealed with the great increase of the open-circuit voltage (Voc), short-circuit current (Jsc), and photoelectric conversion efficiency (η) of the prepared cells; the efficiency (η) was improved from 5.42% of a commercial TiO2 photoelectrode to 7.47% of an unmodified N-doped electrode, and to 9.03% of a N-doped and CaCO3 surface modified electrode. An enhanced photoresponse in N-doped TiO2 nanoparticles generate more photo-excited electrons in adsorbed dye, as supported by measured UV–vis diffuse reflectance spectra and incident photon to current conversion efficiency (IPCE). A successive CaCO3 surface modification then form a barrier on the surface of N-doped TiO2 particles, suppressing charge recombination of photo-generated electrons from N-doped TiO2 to dye or electrolyte, and thus extending their life time in the electrode, as supported by electron impedance spectroscopy (EIS). Furthermore, the higher basicity of the CaCO3 modified TiO2 facilitates the dye adsorption, as supported by the direct measurement of the amount of adsorbed dye.

N-doped titania powders prepared by different nitrogen sources and their application in quasi-solid state dye-sensitized solar cells

SUMMARY Nitrogen-doped TiO2 nanocrystalline particles are synthesized by a microwave-assisted hydrothermal growth method using different amines (Dipropylamine, Diethanolamine and Ammonium hydroxide) as nitrogen sources. Characterization of the nanoparticles was performed with X-ray diffraction, UV–vis diffuse reflectance spectroscopy, Field Emission Scanning Electron Microscopy and X-ray Photoelectron Spectroscopy. The prepared N-doped TiO2 nanoparticles exhibit pure anatase phase with average diameter of 9 nm and reduced optical energy gap compared to undoped TiO2. Immobilization of N-doped and pure TiO2 nanoparticles on SnO2:F conductive glass substrates was successfully performed by using doctor-blade technique and paste of the aforementioned nanoparticles. A series of N-doped TiO2 photoelectrodes with varying N dopant source and concentrations were fabricated for quasi-solid state dye-sensitized solar cells. The N-doped solar cells achieve an overall conversion efficiency ranging from 4.0 to 5.7% while undoped TiO2 showed 3.6%. The basic difference to the electrical performance of the cells is focused to the enhancement in the current density of N-doped TiO2-based cells which was from 11% to 58% compared with undoped TiO2 cells. Current densities were directly proportional with nitrogen doping level in TiO2 lattice which differs depending on the amine source nature such as basicity differences, hydrogen bonding abilities and steric inherences. Copyright © 2013 John Wiley & Sons, Ltd.

Combination of photocatalytic and photoelectro-Fenton/citrate processes for dye degradation using immobilized N-doped TiO2 nanoparticles and a cathode with carbon nanotubes: Central composite design optimization

In this report, commercial TiO2 nanoparticles were doped with nitrogen by a manual grinding method using urea. The prepared catalyst was characterized by X-ray diffraction (XRD), diffuse reflectance spectra (DRS), and transmission electron microscopy (TEM). N-doped TiO2 was immobilized on ceramic plates by methyl tri-methoxy silane. Next, multi-walled carbon nanotubes (CNTs) were stabilized on carbon paper to fabricate the cathode. Scanning electron microscopy (SEM) was employed to confirm stabilization of the CNTs. The prepared cathode and immobilized catalyst were utilized for the degradation of C.I. Direct Red 23 (DR23) by the photoelectro-Fenton (PEF) process in the presence of citrate (Cit) combined with a photocatalytic process. The coupled PEF/Cit/N-TiO2 process could be performed under visible light, not only due to the formation of iron–citrate complexes, but also because of the incorporation of nitrogen to the crystalline structure of TiO2 and the generation of TiO2 complexes with electrogenerated H2O2. Results demonstrated that the degradation efficiency of DR23 (20mg/L) using the identical operational conditions, followed a decreasing order of: PEF/Cit/N-TiO2>PEF/Cit>PEF>EF>N-TiO2. Eventually, a model was developed by the central composite design (CCD) method, describing the degradation efficiency as a function of the operational parameters.

Effect of valence band energy on the photocatalytic performance of N-doped TiO2 for the production of O2 via the oxidation of water by visible light

Five types of N-doped TiO2 (TiO2−xNx, x=0, 0.005, 0.015, 0.03, and 0.06) nanoparticles were prepared and evaluated for use as a catalyst for production of O2 via the oxidation of water by irradiation with visible light. The resulting materials were characterized using ultraviolet diffuse reflectance spectroscopy (UV-DRS), electrochemical impedance spectroscopy (EIS), and photoluminescence (PL) techniques. The results indicate that a change in band gap energy (Eg) as a function of N-doping level in the materials resulted in a change in the valence band (VB) level, but not the conduction band (CB) level. The very small upward shift in VB enhanced the photocatalytic formation of OH radicals produced by irradiation with visible light. In addition, the small amount N-dopant (up to 3at%) incorporated into the samples accelerated the evolution of O2, rather than the formation of OH species. The incorporation of larger amounts of N-dopant in the TiO2−xNx reduced the rates of both O2 evolution and OH formation, due to the small energy level of VB and the short life time of the photo-generated charges. The performance of TiO1.97N0.03 nanoparticles with an Eg value of 2.8eV was outstanding for the evolution of O2 from the water under the experimental conditions used.

Decolourisation of Metanil Yellow by visible-light photocatalysis with N-doped TiO2 nanoparticles: influence of system parameters and kinetic study

A nitrogen-doped photocatalyst (N-TiO2) is prepared from 15% TiCl3 and 25% aqueous NH3 solution as precursor. The synthesised material is characterised by XRD, BET, TEM, DRS and XPS and is used for photocatalytic decolourisation of Metanil Yellow under visible-light illumination. The experimental parameters, viz, photocatalyst dose, initial dye concentration and solution pH influence the decolourisation process. At pH 3.5, N-TiO2 can decolourise almost 89% of the dye at equilibrium within 240 min. COD study reveals ∼92% mineralisation of the dye in 360 min of irradiation. The photocatalytic reaction is allowed to proceed only after the attainment of adsorption equilibrium between N-TiO2-Metanil Yellow. The adsorption is carried out by batch process under different experimental conditions, namely, N-TiO2 dose, initial dye concentration and solution pH. The adsorption process attains equilibrium within 60 min and follows Lagergren first-order kinetics. On the other hand, the photocatalytic decolourisation of Metanil Yellow is suitably fitted with the modified Langmuir–Hinselwood model. Modification of TiO2 improved the decolourisation of the dye by ∼8 times compared to TiO2 P25.

CO Adsorption and Oxidation on N-Doped TiO2 Nanoparticles

In order to oxidize CO to CO2 during the process of steam pyrolysis nuclear graphite waste, the adsorption and oxidation of a CO molecule on undoped and N-doped TiO2 nanoparticles has been studied by first-principles calculations, including the adsorption energies, bond lengths, local density of states (LDOSs), and the charge density difference (CDD). In the adsorption process, two electrons transfer from CO to the particle resulting in the reduction of the Ti sites. CO2 and carbonate form during the adsorption process on the dangling oxygen atom. The CO over the undoped and N-doped nanoparticles forms CO2 by detaching the dangling oxygen atom. Less than 0.22 eV energy gained can drive the CO2 away to a distance greater than 3.01 Å. Therefore, the CO molecule can be oxidized to CO2 by TiO2 nanoparticle, and the physically adsorbed CO2 molecule can spontaneously dissociate at room temperature, apart from the energies released in the adsorption process. The adsorption energy for an undoped particle is −0.93 eV, while that for an N-doped particle is −2.47 eV or −2.52 eV. N-doped nanoparticles have stronger oxidation ability. The doped nitrogen site (N site) in N-doped nanoparticles is also a chemical adsorption site. N-doped anatase (101) surfaces have stronger adsorption ability than the undoped surface, but weaker than the N-doped anatase nanoparticles adsorption. The results show that the N-doped anatase particles can react with CO molecule more efficiently.