Nb2O5 Samples Research Articles

Effect of the Synthesis Parameters on the Physicochemical Properties and Photocatalytic Performance of Nb2O5 to Water Treatment and H2 Production

Nb2O5 is a promising photocatalyst for degradation of organic pollutants and production of H2 (renewable and green fuel) from water is an alternative to overcome environmental and energy concerns. Therefore, the effect of Nb precursor and synthesis method on the Nb2O5 physicalchemical properties and photocatalytic performance were investigated in this work. X-ray diffraction and Raman spectroscopy results showed that synthesis parameters had a significant impact on the structural properties of the materials obtained. The synthesis parameters were able to tune Nb2O5 crystalline phase, morphology and specific surface area. Nb2O5 sample obtained by hydrothermal method resulted in materials with smaller size and homogeneous particles compared to the other samples, which resulted in a higher specific surface area (200 m2 g-1) and surface hydroxylation. Nb2O5 samples were active to promote both the degradation of Rhodamine B and amiloride, the specific surface area and surface hydroxylation play a key role in the performance of the materials. The most active sample for organic pollutant degradation was also active in H2 production, additionally, the decoration with Pt nanoparticles increased its performance. This work describes the effect of synthesis parameters of Nb2O5 on its photocatalytic properties and demonstrates the potential application of this material in heterogeneous photocatalysis.

Activation and hydrogen storage properties of Mg-based composites synthesized by catalytic mechanochemical hydrogenation strategy

To ameliorate the activation performance and absorption/desorption properties, Mg-based composites are prepared via catalytic mechanochemical hydrogenation (CMCH) strategy by TiF3 or Nb2O5 or both. The results show that multiple H2 filling mechanochemical hydrogenation (MCH) way is in favour of the transformation from Mg to MgH2. The hydrogenation process and hydrogenation degree of Mg can be effectively accelerated via CMCH with TiF3 or Nb2O5 or both. The complete hydrogenation time for CMCH Mg–TiF3 and Mg–TiF3–Nb2O5 is compressed to 12 h, which is much shorter than those of CMCH Mg–Nb2O5 and Mg systems. The hydrogenation capacities at 3rd activation cycle of 12 h CMCH Mg–TiF3, Mg–Nb2O5 and Mg–TiF3–Nb2O5 are 5.87, 5.74 and 5.38 wt%, which corresponding to 81.3%, 79.5% and 74.5% activation rates. The hydrogenation capacities at 3rd activation cycle of 20 h CMCH Mg–TiF3, Mg–Nb2O5 and Mg–TiF3–Nb2O5 are 6.56, 7.08 and 7.18 wt% with 90.9%, 98.1% and 99.4% activation rates. The absorption capacities of CMCH Mg–TiF3, Mg–Nb2O5 and Mg–TiF3–Nb2O5 at 350 °C under 3 MPa pressure within 0.5 h are 5.75, 5.74 and 4.67 wt%. The dehydrogenation peak temperatures of γ-MgH2 reduce to 367.37 °C and 366.59 °C and the initial desorption temperatures are 355.77 °C and 351.39 °C of 12 h and 20 h CMCH Mg–TiF3–Nb2O5 at 5 °C/min heating rate. The lowest dehydrogenation peak temperatures of 391.73 °C and 389.81 °C are achieved by 12 h and 20 h CMCH Mg–TiF3–Nb2O5 samples. The catalytic mechanochemical hydrogenation has been proved to be a feasible and effective strategy for fast acquisition of Mg-based hydride composites with expected hydrogen storage performance.

Surface modification of T-Nb2O5 with low-crystallinity Nb2O5 to enhance photocatalytic degradation of rhodamine B

This work demonstrates the obtainment of an orthorhombic Nb2O5 (T) heterostructure synthesized by the polymeric precursor method coated with low-crystallinity Nb2O5 synthesized by the microwave-assisted hydrothermal method. The sample was submitted to the photocatalytic degradation test using Rhodamine B (RhB) dye decolorization under UVC irradiation for 60 min. The heterostructure sample demonstrated a significant enhancement in photocatalytic performance as compared to orthorhombic Nb2O5, achieving complete degradation of RhB within 60 min. In contrast, the orthorhombic Nb2O5 sample only discolored 26% in the same duration.

Niobium pentoxide as an adsorbent for methylene blue removal: Synthesis, characterization and thermal stability

This study investigated the synthesis of niobium pentoxide (Nb2O5) by peroxide oxidation with hydrothermal treatment and evaluated its application for adsorption of the organic pollutant methylene blue (MB) in aqueous medium. Hydrothermal treatment was performed at 150 °C for different times (4, 12, and 24 h). The resulting materials were characterized by X-ray diffractometry, Raman spectroscopy, thermogravimetry, differential scanning calorimetry, Fourier-transform infrared spectroscopy (FTIR), N2 adsorption isotherm analysis, zeta-potential analysis, and scanning electron microscopy (SEM). Nb2O5 samples had high surface area (174 m2 g−1) and orthorhombic crystal structure. FTIR revealed that an increase in synthesis time produced an increase in surface hydroxylation. Particles dispersed in water had zeta-potential values lower than −31.3 mV, suggesting colloidal stability in aqueous suspension. SEM analyses showed no significant variation in nanoparticle morphology as a function of synthesis time. MB adsorption studies using the sample treated at 150 °C for 24 h showed that the adsorption was higher at pH 6.0, and the process follows pseudo-second order kinetics, suggesting chemical diffusion as the dominant process. The Freundlich isotherm model provided the best fit to experimental data. Thermal analyses indicated a phase transition at about 600 °C, corroborated by analysis of samples after calcination at 500 and 700 °C. Thus, the obtained materials have high specific surface area, adsorption capacity, suspension stability, and thermal stability.

Modular calcination strategy to construct defect-rich nitrogen-doped Nb2O5 for boosting photocatalytic oxidation of cyclohexane to cyclohexanone in solvent-free conditions

The partial oxidation of cyclohexane (CHA) with oxygen to cyclohexanone (CHA-one) is one of the most transformation in the chemical industry in view that CHA-one is an irreplaceable raw material in the production of nylon. Herein, hydrogen, vacuum and air modules combined with ammonia module, respectively, were used to construct defect-rich nitrogen-doped Nb2O5. And, the calcination order and temperature were also considered to establish a modular calcination strategy. A series of modified N-doped Nb2O5 were prepared by the proposed strategy, which were used to catalyze the photo-oxidation of CHA in solvent-free and room temperature conditions. Among these modified N-doped Nb2O5 samples, the HN-Nb2O5 possessed abundant chemical defects of oxygen vacancies and Nb4+, and achieved the best photocatalytic performance. Surprisingly, HN-Nb2O5 achieved an amount of 130.35 μmol for CHA-one, which was approximately 2.2 and 26 times that of the pure Nb2O5 and commercial Nb2O5, respectively, with up to 96.68% selectivity to CHA-one. The outstanding photocatalytic performance of the HN-Nb2O5 can be ascribed to the presence of chemical defect-rich and the NOx species, enhanced light absorption and effective electron-hole separation. DFT calculations explained the promotion of the chemical defects and N doping on Nb2O5 photocatalytic activity in terms of the band electron and band-gap level. The results of EPR analysis and scavenger tests found that e− is the main active species resulted in photocatalytic activity, while O2− is the dominant active species for producing CHA-one in the photo-oxidation of CHA. The present work developed an efficient strategy to construct the defect-rich N-doped metal oxide for the improved photocatalytic oxidation of hydrocarbon.

Phosphate doping as a promising approach to improve reactivity of Nb2O5 in catalytic activation of hydrogen peroxide and removal of methylene blue via adsorption and oxidative degradation

This study is devoted to the evaluation of the influence of phosphate dopants on the reactivity of Nb2O5-based nanomaterials in the combined catalytic activation of H2O2 and the elimination of methylene blue (MB) from an aqueous solution via adsorption and chemical degradation. For this purpose, several niobia-based catalysts doped with various amounts of phosphate were prepared by a facile hydrothermal method and subsequent calcination. Phosphate doping was shown to strongly enhance the ability of Nb2O5 to activate H2O2, as well as to adsorb and degrade MB. The most pronounced differences in the reactivity of the parent Nb2O5 and phosphate-doped samples were observed under strongly acidic conditions (pH ~ 2.4), at which the most active modified catalysts (Nb/P molar ratio = 5/1) was approximately 6 times more efficient in the removal of MB. The observed enhancement of reactivity was attributed to the increased generation of singlet oxygen 1O2, which was identified as the main oxidizing agent responsible for efficient degradation of MB. To our knowledge, it is the first report revealing that phosphate doping of Nb2O5 resulted in an improved activity of niobia in the adsorption and degradation of organic pollutants.

Photoreduction of Cr(VI) in wastewater by anodic nanoporous Nb2O5 formed at high anodizing voltage and electrolyte temperature.

In this study, nanoporous anodic film was produced by anodization of niobium, Nb in a fluoride ethylene glycol electrolyte. The effect of anodization voltage and electrolyte temperature was studied to find an optimum condition for circular, ordered, and uniform pore formation. The diameter of the pores was found to be larger when the applied voltage was increased from 20 to 80V. The as-anodized porous film was also observed to comprise of nanocrystallites which formed due to high field-induced crystallization. The nanocrystallites grew into orthorhombic Nb2O5 after post-annealing treatment. The Cr(VI) photoreduction property of both the as-anodized and annealed Nb2O5 samples obtained using an optimized condition (anodization voltage: 60V, electrolyte temperature: 70°C) was compared. Interestingly, the as-anodized Nb2O5 film was found to display better photoreduction of Cr(VI) than annealed Nb2O5. However, in terms of stability, the annealed Nb2O5 presented high photocatalytic efficiency for each cycle whereas the as-anodized Nb2O5 showed degradation in photocatalytic performance when used continually.

Fabrication and Characterization of Nb<sub>2</sub>O<sub>5</sub> Dopant Al Thin Films Prepared by DC Reactive Plasma Sputtering Technique

The development of niobium oxide (Nb2O5) thin films is an important work as a result of wide applications of this oxide in the field of material science and thin-film applications. In this study, thin-film microstructures of aluminum (Al)-doped Nb2O5 were prepared by DC plasma sputtering on glasses substrate. The ratio of doping was (0.5, 1, and 1.5) wt. % Al. The obtained samples were thermally treated at 450 °C. Characterized and analyzed the physical properties by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), atomic force microscopy (AFM), and UV-Visible spectroscopy for optical properties investigation. Results showed that the average crystalline size of Nb2O5:0.5%Al film was found at 26.47 nm and the structure was a monoclinic phase for all samples. The distribution of grain size was found lower than 36.3 nm and uninformed particles on the surface. The analyzed optical properties showed the absorption decreased from 0.46 to 0.05 with increasing the wavelength and Low energy gap values decreased from 3.10 eV for Nb2O5 samples to 2.84 eV for 1.5%Al samples. In general, the doping by aluminum improved the physical properties of Nb2O5 films.

Flash cold sintering of Nb2O5: polarity and electrolyte effects

ABSTRACT We report on a novel consolidation technique based on the combination of a liquid (cold sintering) and electricity (flash sintering). The evolution of hydrogen from electrolysis of the solvent triggered the Flash Cold Sintering (FCS) event without need for external heating. Electrochemical effects became pronounced in the presence of acetic acid solution as the electrolyte had an increased conductivity compared to pure water. By adjusting the acetic acid molar concentration to 0.5 M and by inverting the polarity during FCS a 5 mm diameter 0.8 mm thick Nb2O5 sample was evenly sintered up to 99% in 100 s at a temperature as low as 350°C. Conventional sintered counterparts achieved a 95% relative density when dwelled for 240 min at 1400°C. The inherent complexity of the proposed FCS approach resulted in enhanced densification and weakly translucent samples.

Topological synthesis of crystalline Ag/T‐Nb2O5 nanobelts with enhanced solar photoelectrochemical properties for splitting water

AbstractThe tetragonal phase Nb2O5 (T‐Nb2O5) nanobelts with preferentially exposed the (010) facet have been successfully prepared for the first time by insitu topological reaction using the KNb3O8 nanobelts as the precursor. Meanwhile, the transformation mechanism of the crystal structure and morphology from the layered KNb3O8 nanobelt to the T‐Nb2O5 nanobelt was revealed in detail by using XRD, FE‐SEM, TEM, HRTEM, SAED, UV‐vis DRS, EDX, XPS, and Raman spectra. In addition, Ag deposited T‐Nb2O5 (Ag/T‐Nb2O5) nanobelts were prepared by photo‐reduction reaction. The photoelectrochemical properties of the T‐Nb2O5 nanobelts and Ag/T‐Nb2O5 nanobelts as a photocatalyst were evaluated by splitting water under simulated sunlight. The results show that the photocurrent density generated by the prepared Ag/T‐Nb2O5 sample is 48.1 µA∙cm−2, which is 2.3 times that of the T‐Nb2O5 sample, and the prepared tetragonal phase T‐Nb2O5 nanobelts produce a photocurrent value 1.5 times that of the contrast orthogonal phase O‐Nb2O5 nanosheets. It indicates that the (010) facet of the tetragonal phase Nb2O5 is one of the highest photocatalytic active surfaces, and the visible light utilization efficiency of the T‐Nb2O5 nanobelt with Ag deposited on the surface has been significantly improved, which implies that it has potential applications in the field of photocatalysis.

Facile synthesis of hollow urchin-like Nb2O5 nanostructures and their performance in dye-sensitized solar cells

In present study, hollow urchin-like nanostructures of Nb2O5 with elongated nanofilaments as photoanode material for dye-sensitized solar cells (DSSCs) are successfully synthesized at different reaction times (viz. 12, 24, and 40 h, respectively, named as samples NB-1, NB-2, and NB-3) using facile hydrothermal route. We have studied the significant influence of hydrothermal reaction time on the structural, optical, morphological, and electrical properties. The photovoltaic performance of different samples is understood from response of current-potential (J-V) curve and incident photon-to-current efficiency (IPCE) while charge recombination behavior and resistance of the cells are studied by electrochemical impedance spectroscopy (EIS). The X-ray diffraction (XRD) study shows the orthorhombic crystalline form for the synthesized samples. Electron microscopy studies confirm the formation of porous spherical morphology with hairy filaments protruding outward. Size of urchin-like particle is found to be in the range of about 1 μm diameter, and the filaments emerging out from the surface of hollow spheres are seen to be 30–70 nm long and 5–20 nm in diameter. The DSSCs fabricated from the resultant nanostructures show the better photovoltaic performance with Nb2O5 sample synthesized at 24-h reaction time. The Jsc and efficiency for NB-2 are 8.24 mAcm−2 and 3.58% respectively, which are better than corresponding samples synthesized at the reaction time of 12 h and 40 h, respectively. These photovoltaic results obtained from the DSSCs fabricated using Nb2O5 nanostructures are comparatively exciting with TiO2 spheres. By further optimizing reaction conditions, it is expected that niobium pentoxide can emerge as better semiconductor oxide for photovoltaic and optical devices.

Temperature dependent conductivity and broadband dielectric response of precursor-derived Nb2O5

Different polymorphs of niobium pentoxide (Nb2O5) were synthesized using niobium ethoxide as a precursor by varying the pyrolyzing temperature. The room temperature X-ray diffractograms revealed the irreversible phase evolution from amorphous to pseudohexagonal (823 K) to orthorhombic (1023 K) and to monoclinic crystal structure (1223 K). While phase evolution was also confirmed by thermogravimetry and dilatometry, Raman spectroscopy clearly suggested complete elimination of free carbon in the pyrolysed ceramics. The sintering conditions were optimized to produce a highly dense (>95%) thermodynamically stable monoclinic Nb2O5. The electrical properties of stable monoclinic Nb2O5 sample were thoroughly studied. The monoclinic Nb2O5 was found to have a dielectric constant of around 28 with a dielectric loss of 0.008 at room temperature and at 100 kHz. At low measurement frequencies, an anomalous increase in the effective dielectric permittivity with increasing temperature was observed. Large values of the ε’ are associated with polarization due to the accumulation of free electrons at the grain boundaries. An analysis of the dispersion curves of Nb2O5 revealed that two relaxation processes are responsible for the observed anomalies, and the temperature dependencies of their parameters (dielectric strength, relaxation time and spectrum broadening parameter) were determined. The low-frequency process (relaxation time τ0 ~ 0.45 s), which makes the largest contribution to the dielectric constant, was apparently due to the inhomogeneous conductivity of ceramics. It was revealed that the DC conductivity of ceramics has thermoactivation character with activation energy of about 660 meV and was determined by the oxygen vacancies.

Pt–TiO2–Nb2O5 heterojunction as effective photocatalyst for the degradation of diclofenac and ketoprofen

Pt–TiO2–Nb2O5 heterojunction was synthetized and studied for the photocatalytic removal of diclofenac (DCF) and ketoprofen (KTF) under UV light irradiation. The physical-chemical properties of the prepared catalysts were analysed by different characterization techniques revealing that the lowest platinum nanoparticle size and the better metal distribution was observed in Pt–TiO2–Nb2O5 sample. The Pt–TiO2–Nb2O5 heterojunction possessed the best photocatalytic activity toward both the photodegradation and mineralization of the two selected pollutants. The optimal photocatalyst showed a DCF and KTF mineralization rate of 0.0555 and 0.0746 min−1, respectively, which were higher than those of Pt–TiO2 (0.0321 min−1 for DCF and 0.0597 min−1 for KTF). The experiments driven to analyse the effects of free radical capture showed that ·OH, ·O2− and h+ have a primary role in reactive during the photocatalytic reaction. The improved photocatalytic performances of the Pt–TiO2–Nb2O5 heterojunction could be argue by a direct Z-scheme mechanism in which the Pt0 nanoparticles could act as a bridge between TiO2 and Nb2O5, improving the electron-hole separation and, ultimately, enhancing the photocatalytic removal rate of both DCF and KTF.

One-Step Plasma Synthesis of Nb2 O5 Nanofibers and their Enhanced Photocatalytic activity.

Fiberform nanostructured niobium (Nb) was fabricated by one step helium (He) plasma irradiation. He ion implantation formed He nano-bubbles on a Nb plate and led to formation of protrusions while migrating in Nb matrix; fiberform nanostructures (FN) were grown when the fluence became high (>1026 m-2 ). The necessary conditions for the formation of Nb FN were revealed to be the surface temperature range of 900-1100 K and the incident ion energy higher than 70 eV. The sample was oxidized at 573-773 K in an air atmosphere, and Pt nanoparticles were photo-deposited on the Nb2 O5 samples. The surface was analyzed by scanning electron microscope, transmission electron microscope, x-ray photoelectron spectroscopy, and ultraviolet-visible spectrophotometry. Photocatalytic activity of the fabricated materials was studied using methylene blue (MB) decolorization process. An enhanced photocatalytic performance was identified on FN Nb2 O5 substrate with Pt deposition.

Acidic surface niobium pentoxide is catalytic active for CO2 photoreduction

In this paper, we report for the first time the significant photocatalytic activity of Nb-based materials for CO2 reduction. Nb2O5 catalysts were prepared through a modified peroxide sol-gel method using different annealing temperatures, showing activity for CO2 photoreduction in all conditions. The activity and selectivity of the Nb2O5 samples were directly related to their surface acidity: high surface acidity prompted conversion of CO2 to CO, HCOOH, and CH3COOH; low surface acidity prompted conversion of CO2 to CH4. The results also indicated that CO is the main intermediate species of the CO2 photoreduction in all conditions. We have uncovered the role played by the surface acidity of Nb2O5 and the mechanism behind its performance for CO2 photoreduction.

Water effects on the acidic property of typical solid acid catalysts by 3,3-dimethylbut-1-ene isomerization and 2-propanol dehydration reactions

Two model reactions, namely the Brønsted-acidity-specific skeletal isomerization of 3,3-dimethylbut-1-ene for evaluating the Brønsted acidity and dehydration of 2-propanol for the overall acidity at the catalyst surface, were employed in this work to measure the effect of water on the surface acidic property of typical solid catalysts (HZSM-5, γ-Al2O3 and Nb2O5). For the isomerization reaction, water addition in the reaction feed produced little effect on the catalysis of HZSM-5 but significantly positive effect on the catalysis of Nb2O5; the typical Lewis acidic γ-Al2O3 showed no activity for this reaction in either the presence or absence of water. For the dehydration reaction, the effect of water was generally negative on the catalysis of every catalyst, demonstrating that water presence resulted in poisoning more or less of the Lewis acidity on the catalyst surface. Water poisoning of the Lewis acidity on Nb2O5 also resulted in generation of Brønsted acidity and the higher the H2O partial pressure (or H2O-to-substrate ratio) the higher the newly generated Brønsted acidity. However, generation of Brønsted acidity did not happen on γ-Al2O3 and HZSM-5, regardless of the H2O partial pressure. Three Nb2O5 samples with varying calcination temperature were involved, and their behavior clearly indicated that the water effects on Nb2O5 also depended sensitively on the sample calcination temperature. Moreover, water presence increased the activation energy and selectivity for di-isopropyl ether of the dehydration reaction over γ-Al2O3 and Nb2O5, and thus affected the acidity distribution at the catalyst surface during the reaction.

G-C3N4/Nb2O5 heterostructures tailored by sonochemical synthesis: Enhanced photocatalytic performance in oxidation of emerging pollutants driven by visible radiation

In this study, g-C3N4/Nb2O5 heterostructures were successfully prepared by a sonochemical method based on surface charge-induced heteroaggregation. Under visible irradiation, the heterostructured g-C3N4/Nb2O5 samples exhibited higher activity in the photooxidation of the drug amiloride (AML) and rhodamine B dye (RhB), compared to the pure g-C3N4 and Nb2O5 phases. The enhanced photocatalytic activity of the heterostructures could be attributed to the effective formation of heterojunctions between the g-C3N4 and Nb2O5 semiconductors, causing the migration of photogenerated electrons and holes, hence increasing their lifetimes. Formation of the type-II heterostructure was confirmed by time-resolved photoluminescence, in which the 3CN:1Nb heterostructure showed the longest electron/hole pair lifetime. The 3CN:1Nb and 1CN:3Nb heterostructures exhibited high stability even after four cycles of reuse in RhB dye and drug AML oxidation, respectively. In summary, the combination of g-C3N4 with Nb2O5 to produce a type-II heterostructure is a good strategy to overcome important challenges in photocatalysis.

Reactive dynamics analysis of critical Nb2O5 sputtering rate for drum-based metal-like deposition.

Drum-based metal-like film deposition for oxide was investigated using single wavelength in situ monitoring. The data were used to investigate the oxidation mechanism using combined second-order kinetic and parabolic models. A critical Nb2O5 deposition rate of 0.507nm/s was found at drum rotation of 1rev/s. However, Nb2O5 samples prepared at varying deposition rates showed that the deposition rate must be much lower than the critical deposition rate to achieve reasonable absorption. Thus simulation for the volume-fraction of metal in the oxide layer was done using effective medium approximation and a distribution function. Simulation gave high agreement with experimental results and allows the prediction of extinction coefficients at various deposition rates.

Nb2O5 Nanostructure Evolution on Nb Surfaces via Low-Energy He+ Ion Irradiation.

We propose low-energy, broad-beam He+ ion irradiation as a novel processing technique for the generation of Nb2O5 surface nanostructures due to its relative simplicity and scalability in a commercial setting. Since there have been relatively few studies involving the interaction of high-fluence, low-energy He+ ion irradiation and Nb (or its oxidized states), this systematic study explores both effects of fluence and sample temperature during irradiation on resulting surface morphology. Detailed normal and cross-sectional scanning electron microscopy (SEM) studies reveal subsurface He bubble formation and elucidate potential driving mechanisms for nanostructure evolution. A combination of specular optical reflectivity and X-ray photoelectron spectroscopy (XPS) is also used to gain additional information on roughness and stoichiometry of irradiated surfaces. Our investigations show significant surface modification for all tested irradiation conditions; the resulting surface structure size and geometry have a strong dependence on both sample temperature during irradiation and total ion fluence. Optical reflectivity measurements on irradiated surfaces demonstrate increased surface roughening with increasing ion fluence, and XPS shows higher oxidation levels for samples irradiated at lower temperatures, suggesting larger surface roughness and porosity. Overall, it was found that low-energy He+ ion irradiation is an efficient processing technique for nanostructure formation, and surface structures are highly tunable by adjusting ion fluence and Nb2O5 sample temperature during irradiation. These findings may have excellent potential applications for solar energy conversion through improved efficiency due to effective light absorption.

Preparation of gold nanoparticles supported on Nb2O5 by deposition precipitation and deposition reduction methods and their catalytic activity for CO oxidation

Nanoparticulate gold catalysts supported on niobium oxides (Nb2O5) were prepared by different deposition methods. The deposition precipitation (DP) method, DP method with urea, deposition reduction (DR) method and one-pot method were used to prepare a 1 wt% Au/Nb2O5 catalyst. Layered-type Nb2O5 synthesized by a hydrothermal method (Nb2O5(HT)) was the most suitable as a support among various types of Nb2O5 including commercially available Nb2O5 samples. It appeared that the large BET surface area of Nb2O5(HT) enabled the dispersion of gold as nanoparticles (NPs). Gold NPs with a mean diameter of about 5 nm were deposited by both the DP method and DR method on Nb2O5(HT) under an optimized condition. The temperature for 50% CO conversion for Au/Nb2O5(HT) prepared by the DR method was 73 °C. Without deposition of gold, Nb2O5(HT) showed no catalytic activity for CO oxidation even at 250 °C. Therefore, the enhancement of the activity by deposition of gold was remarkable. This simple Au/Nb2O5 catalyst will expand the types of gold catalysts to acidic supports, giving rise to new applications.