Nb Incorporation Research Articles

Doped SnO2 thin films fabricated at low temperature by atomic layer deposition with a precise incorporation of niobium atoms

Nb-doped SnO2 (NTO) thin films were synthesized by atomic layer deposition technique at low temperature (100 °C). For an efficient incorporation of the Nb atoms, i.e. fine control of their amount and distribution, various supercycle ratios and precursor pulse sequences were explored. The thin film growth process studied by in-situ QCM revealed that the Nb incorporation is highly impacted by the surface nature as well as the amount of species available at the surface. This was confirmed by the actual concentration of the Nb atom incorporated inside the thin film as determined by XPS. Highly transparent thin films which transmit more than 95% of the AM1.5 global solar irradiance over a wide spectral range (300–1000 nm) were obtained. In addition, the Nb atoms influenced the optical band gap, conduction band, and valence band levels. While SnO2 thin film were too resistive, films tuned to conductive nature upon Nb incorporation with controlled concentration. Optimal incorporation level was found to be ⩽1 at.% of Nb, and carrier concentration reached up 2.5 × 1018 cm−3 for the as-deposited thin films. As a result, the high optical transparency accompanied with tuned electrical property of NTO thin films fabricated by ALD at low temperature paves the way for their integration into temperature-sensitive, nanostructured optoelectrical devices.

Influence of Nb on the hydrogen-assisted cracking behaviour in multiphase stainless steel: Phase fractions, stacking fault energies, and nanosized NbC precipitation

Nb alloying has been reported to deteriorate the hydrogen embrittlement resistance of multiphase steels, which contrasts to the case of single-phase metallic materials. This study clarifies the impact of Nb alloying on the hydrogen embrittlement behaviour of a novel multiphase stainless steel. The findings revealed a 17 % reduction in the hydrogen embrittlement sensitivity upon Nb incorporation. It was found that higher austenite fractions in the Nb-bearing steels impeded hydrogen ingress. The austenite phase in such Nb-bearing steels possesses a higher stacking fault energy, thereby delaying martensitic transformation and crack initiation. The precipitation of nanometre-sized NbC in the matrix obstructed hydrogen diffusion, which indirectly inhibited crack initiation and propagation.

Fine tuning of Nb-incorporated TiO2 thin films by atomic layer deposition and application as efficient electron transport layer in perovskite solar cells

Access to finely tuned thin films that can act as electron transport layer (ETL) and adapt to the absorber composition and whole cell fabrication process is key to achieve efficient perovskite-based solar cells. In this study, the growth of mixed niobium-titanium oxide (Nb-TiO2) thin films by atomic layer deposition and its use to extract photogenerated electrons is reported. Films were obtained at 200 °C from titanium (IV) i-propoxide, (t-butylimido)tris(diethylamido)niobium(V), and water by introducing Nb2O5 growth cycle in a TiO2 matrix. Process parameters (order of precursor introduction, cycle ratio) were optimized; the growth mechanism and the effective Nb incorporation were investigated by an in situ quartz crystal microbalance and x-ray photoelectron spectroscopy. The composition, morphology, structural, and optoelectronic properties of the as-deposited films were determined using a variety of characterization techniques. As a result, a fine control of the film properties (between TiO2 and Nb2O5 ones) could be achieved by tuning Nb content. To allow a successful implementation in solar devices, a comprehensive annealing study under several conditions (temperatures, various atmospheres) was conducted leading to an evolution of the optical properties due to a morphological change. Ultimately, the incorporation of these 15 nm-thick films in mesoscopic perovskite solar cells as ETL shows an improvement of the cell performances and of their stability with increasing Nb content, in comparison of both TiO2 and Nb2O5 pure compounds, reaching power conversion efficiency up to 18.3% and a stability above 80% of its nominal value after 138 h under illumination.

Niobium doping of CVD-WS2 monolayers using solid precursors with and without salt-KBr as a catalyst: A comparative study

The in situ doping of tungsten disulfide (WS2) monolayers with Niobium (Nb) atoms was obtained through the atmospheric pressure chemical vapor deposition (APCVD) method by controlling the Nb2O5 and WO3 precursors mass ratios. Samples were prepared employing the same growth parameters with and without the use of KBr salt as a catalyst. In both cases, the Nb incorporation quenches the luminescence intensity of the doped samples, and it depends on the Nb2O5:WO3 mass ratio. X-ray photoelectron spectroscopy (XPS) measurements were performed, and the observed redshift at the Fermi level indicated p-type doping. Nb-doped WS2 monolayers synthesized without the use of the catalyst have lower defect density, as revealed by a careful Raman analysis, and are free of agglomerates on their monolayers’ basal plane. The use of KBr as the catalyst increases the average crystal size but also increases the disorder effects compared with samples prepared without the use of salt. The presence of agglomerates of impurities at the surface of doped samples was observed in samples prepared with the use of salt as a catalyst. The controlled synthesis of p-type WS2 with low defect density is essential for developing electronic and photonic devices based on WS2 material.

Effect of Nb Addition on the Corrosion and Wear Resistance of Laser Clad AlCr2FeCoNi High-Entropy Alloy Coatings

Laser clad AlCr2FeCoNiNbx (x = 0, 0.5, 1.0, 1.5, 2.0, with x values in molar ratio) high-entropy alloy (HEA) coatings were fabricated on Q345 carbon steel. This study delves into the impact of Nb incorporation on the reciprocating sliding wear resistance of these laser clad coatings against a Φ6 mm silicon nitride ball. The microstructure of the as-clad AlCr2FeCoNiNbx coatings transformed from a single Face-Centered Cubic (FCC) solid solution (when x = 0) to the hypoeutectic state (when x = 0.5) and progressed to the hypereutectic state (when x ≥ 1.0). This evolution was marked by an increase in the Laves phase and a decrease in FCC. Consequently, the HEA coatings exhibited a gradually increasing Vickers hardness, reaching a peak at HV 820. Despite a decline in corrosion resistance, there was a notable enhancement in wear resistance, and the friction of the HEA coating could be reduced by Nb addition. The phase evolution induced by Nb addition led to a shift in the predominant wear mechanism from delamination wear to abrasive wear. The wear rate of Nb0.5 was impressively low, at 6.2 × 10−6 mm N−1 m−1 when reciprocating sliding under 20 N in air. In comparison to Nb0, Nb0.5 showcased 3.6, 7.2, and 6.5 times higher wear resistance at 5 N, 10 N, and 20 N, respectively. Under all applied loads, Nb1.5 has the lowest wear rate among all HEA coatings. This substantiates that the subtle introduction of Laves phase-forming elements to modulate hardness and oxidation ability proves to be an effective strategy for improving the wear resistance of HEA coatings.

Tuning the acidity of SAPO-34 zeolite through niobium incorporation for enhanced catalytic performance during MTO reaction

SAPO-34 zeolite is commonly used for light olefin production, an important petrochemical, through the methanol-to-olefin (MTO) conversion process. To modify the physicochemical characteristics of the SAPO-34 zeolite, a series of Nb-incorporated SAPO-34 catalysts were synthesized to alter the crystal size and acidity of the catalysts to enhance its MTO catalytic properties. The Nb incorporation reduced crystal size from 4.6 μm to 1.4 μm, with enhanced acidity for the Nb0.005SP catalyst. The catalytic results revealed that the Nb0.005SP catalyst showed remarkably superior MTO conversions, ∼2.5 time as compared with conventional SP catalyst, due to its reduced crystal size, higher surface area and higher acid sites concentration owing to its shorter diffusion pathlength, greater number of exposed active sites and ability to maintain MTO reaction for longer time, respectively. Moreover, the Nb0.005SP catalyst also exhibited a lower hydrogen transfer index-HTI index with a slight slope, leading to slower coking, enhanced light olefine selectivity and a longer lifetime compared to other counterparts.

Cu docking-activated Nb incorporation in multivariate CuO-Nb2O5/CeO2 catalysts for selective reduction of NOx with NH3

Improving the low-temperature selective catalytic reduction of NOx with NH3 (NH3-SCR) meanwhile maintaining N2 selectivity are challenging in the field of catalysis. Herein, we showcase the fabrication of the synergistic catalytic sites in the CuO-Nb2O5/CeO2 catalysts. Impressively, the CuO-Nb2O5/CeO2 is characteristic with abundant oxygen vacancies at the interfacial regions, which facilitate the redox reaction between Ce3+, Nb5+ and Cu2+ with the assistance of surface oxygen, exhibiting high NH3-SCR activity, N2 selectivity and wide temperature window at a gas hourly space velocity of 150,000 h−1. Contrast experiments, EXAFS analysis, in situ infrared and Raman spectroscopy, and theoretical calculations indicate that the introduction of proper copper ions in the CeO2 lattice induces the structure distortion of surface CeO2, improving more niobium ions incorporation into the CeO2. The embedded Nb synergizes Cu and Ce to evoke the generation of newly adsorptive sites for NOx and NH3, thus contributing to the NH3-SCR reaction.

Doping-induced Ti3+ state and oxygen vacancies in TiO2: A single-chip combinatorial investigation

TiO2 is widely recognized as a high performance photocatalyst for photocatalytic applications. Oxygen vacancies (VO) and titanium defects are known to make a significant contribution to the enhanced photocatalytic efficiency of TiO2, accordingly control of these two centers is pivotal to optimizing the surface photochemical activity. In this work, the formation of VO and Ti3+ ions induced by n-type doping of TiO2 with Nb is demonstrated using a combinatorial investigation approach. Chemical Beam Vapour Deposition (CBVD) is used to fabricate Nb concentration-graded (NbxTi1-x)O2 anatase films with 0.009 ≤ x ≤ 0.033 over a 5 mm length on a single chip. Cathodoluminescence (CL) microanalysis shows the luminescence intensity decreases with increasing Nb concentration; however, the presence of a self-trapped exciton (STE) emission, characteristic of anatase TiO2, indicates that the Nb incorporation does not affect the structural properties of TiO2. Notably, the introduction of Nb donors induces the formation of the signature luminescence bands of VO and Ti3+ at 2.05 and 2.60 eV at 80 K, respectively, and their intensities rise by up to 28% with increasing Nb content. The formation of VO and Ti3+ is attributed to the effect of excess electrons locally produced by Nb donor doping. The thermal activation energies for the STE and defect-related emissions are found to be identical at 32 ± 4 meV, suggesting that the recombination kinetics is mediated by Nb donors. Significantly, we demonstrate that the near-surface VO density can be further increased by two different post-growth treatment approaches: (i) remote hydrogen plasma and (ii) low-energy electron beam irradiation (LEEBI), without effecting the valence state of Ti. Our results open opportunities to optimize the photocatalytic properties of TiO2 by defect engineering.

Stability and physical properties of the K, Na and Nb doped BiFeO3 lead-free system synthesized by the solid state route

A study of the structural, dielectric, and optical properties of the lead-free ceramic compound (1-x)BiFeO3–(x)(K0.5Na0.5)NbO3 [(1-x)BFO-(x)KNN] prepared by the solid-state reaction method is presented. The structural analysis was carried out by performing Rietveld refinement on the X-ray diffraction data showing a distorted rhombohedral structure of the R3c space group for all samples. The presence of all active Raman modes confirms this result. The effect of K, Na, and Nb incorporation in the BFO structure is clearly seen in the scanning electron microscopy micrographs of the samples, and energy dispersive x-ray spectroscopy (EDS) confirms the existence of all elements. Piezoelectric force microscopy analysis reveals a well-defined domain structure for the higher concentrations of KNN as well as ferroelectric switching behavior. The room temperature dielectric response increases with KNN doping. A small hump in the dielectric permittivity vs. temperature plots is observed near 350 °C and is ascribed to a para-antiferromagnetic phase transition at the Nèel temperature. An optical absorption study revealed that tuning of the bandgap energy is possible through controlled doping, as shown in the present case, where the bandgap varies from 2.16 eV for x = 0.0 to 1.93 eV for x = 0.08. The results of this investigation demonstrate that K, Na, and Nb doping is an effective way to enhance the dielectric and optical properties of BFO.

Improving the Glucose to Fructose Isomerization via Epitaxial‐Grafting of Niobium in UIO‐66 Framework

AbstractGlucose to fructose transformation is an essential transformation for the success of biorefinery. Herein, the epitaxial‐grafting of Nb in UIO‐66 significantly improved the fructose yield. Post‐synthesis incorporating Nb in the UIO‐66 phenomenally improved the glucose conversion from 31.1 % to 71.8 % and fructose selectivity from 38.2 % to 71.2 %. The incorporation of Nb was confirmed from the FTIR, HR‐TEM investigation, EDX analysis, and elemental mapping. The XPS analysis distinctly stated the successful incorporation of Nb and generation of Zr−O−Nb oxo clusters in the UIO‐66 framework. The NH3‐TPD provided distinguishable information about the chemical interaction of Nb with the UIO‐66 framework that resulted in the increase of the acid strength after the Nb incorporation in the UIO‐66 catalyst. The content of Nb and reaction parameters, especially temperature and duration, control the glucose to fructose isomerization over glucose to mannose epimerization. The structure‐activity relationship was established, and a reaction mechanism was proposed. The catalyst was recycled five times with only a lower decrease in the fructose yield (47.3 % to 42.2 %) than several reported MOFs catalysts. The activity of the developed catalyst was higher or similar to the reported catalysts. The successful grafting of Nb demonstrates that by swiftly modifying the acidity of the catalyst, a superior activity can be achieved.

Crystallization and conductivity of large-domain Nb-doped TiO2 films prepared by electron beam evaporation

Thin solid films of titania (TiO2), undoped and doped with niobium (Nb), are prepared by reactive electron-beam evaporation at 250 °C and post-heated at temperatures up to 750 °C. Nucleation starts at 375 °C and Nb-doped films largely crystallize at 420 °C, to anatase, as detected by X-ray diffraction (XRD), Raman spectra, and Raman phonon maps. Nb incorporation favors the anatase phase over other crystalline titania phases and leads to an increase in its unit cell volume and a blue shift of the Raman Eg(1) peak. In Raman phonon mapping, films with good conductivity show large domains with similar Raman signals, more than 1 µm in diameter, larger than the crystalline grain diameter of 70 nm obtained from XRD. Such films exhibit a unit cell volume indicating effective Nb incorporation, and a minimum electrical resistivity of about 200 µΩcm, sometimes reached already upon annealing at 350 °C. These findings suggest that the phonon domains consist of about 200 grains with similar crystalline orientation separated by small-angle boundaries.

Enhanced visible-light photocatalytic properties of SnO2 quantum dots by niobium modification

The incorporation of transition metal elements is an effective route to enhance the photocatalytic properties of semiconductors. Tin oxide (SnO2) has a wide band gap of 3.6 eV, which inhibits its applications as visible-light photocatalysts. In this work, niobium-modified SnO2 quantum dots (Nb-SnO2 QDs) are synthesized by a one-step hydrothermal method. The crystal structures and optical properties of the Nb-SnO2 QDs are characterized and the photocatalytic performances are evaluated by the degradation of organic contaminants under visible-light illumination. The rate constant of Nb-SnO2 QDs increases 2.34 times as that of pristine SnO2 QDs in MO degradation. The improved photocatalytic properties are ascribed to the modified band structure by the transition metal. The main active radical is determined to be O2− in the photocatalytic process. The first principle computational models are established based on the experimental characteristics of Nb-SnO2 QDs. The calculation reveals that Nb incorporation brings an impurity energy level in the band structure, which is originated from the 4d orbital electrons of Nb atoms.

Molten Salt Flux Synthesis, Structure determination, Optical, Impedance and Modulus Spectroscopy Characterization of perovskite compound

The chemical Molten Salt Flux process was used for the synthesis of Ba0.97La0.02Ti1-xNb4x/5O3 polycrystalline sample (well-known as BLTi0.93Nb0.056). Doping with Niobium caused significant alterations in the physical properties of BLT ceramic. The XRD analysis revealed that Nb introduction forms a pure perovskite phase and crystallize in the P4/mmm-tetragonal symmetry. The average crystallite size was proven to decrease with the increase in Nb concentration. TEM image showed the formation of particles, where the average grain size decreased with Nb doping. The Nb incorporation into the BLT host lattice was also confirmed by the optical band gap (Eg) value. The optical properties were strongly influenced by Nb doping. The dielectric parameters were subsequently investigated as a function of frequency and d.c bias voltage. The observed dielectric dispersion was interpreted on the basis of Maxwell-Wagner interfacial model and Koop's phenomenological theory. Overall, Nyquist plot shows both bulk and grain boundary effect. The electrical relaxation process occurring in the material has been found to be d.c bias voltage dependent. Modulus analysis has established the possibility of hopping mechanism for electrical transport processes in the system.

Improved carrier mobility of pentacene organic TFTs by suppressed oxide growth at remote interface using nitrogen doping in high-k NdNbO dielectric

Pentacene organic TFTs (OTFTs) using high-k Nd 2 O 3 doped with niobium and/or nitrogen as gate dielectric have been fabricated with gate-dielectric annealing at 200 °C and 400 °C. For 400 °C, the OTFT with only niobium doping in the Nd 2 O 3 gate dielectric shows an obvious improvement in carrier mobility compared with its counterpart with pure Nd 2 O 3 as gate dielectric. Moreover, for the lower temperature of 200 °C, the OTFT with both niobium and nitrogen dopings in the Nd 2 O 3 gate dielectric achieves further improvement with a small threshold voltage of −0.79 V and a high carrier mobility of 2.24 cm 2 /V·s. AFM and XPS reveal that the nitrogen doping, like the niobium doping, can reduce the hygroscopicity of Nd 2 O 3 , leading to a smoother surface of dielectric and thus larger overlying pentacene grains for reducing the scatterings of surface roughness and grain boundary respectively. Besides, highest mobility is achieved for the NdNbON gate dielectric without the best film quality because with nitrogen doping and lower-temperature annealing, a thinner interlayer between the gate dielectric and the Si gate is formed to enhance the electrostatic coupling between them, thus suppressing the phonon scattering on channel carriers caused by the thermal oscillation of the atoms inside the gate dielectric. •For pentacene OTFTs, Nb incorporation in Nd oxide as gate dielectric can reduce its hygroscopicity, leading to a smoother dielectric surface, larger pentacene grains, fewer interface traps and resultant improved performance. •Furthermore with N inclusion in NdNbO, high-performance OTFT can be achieved by using lower-temperature oxide annealing. •Besides passivation effect of nitrogen to further reduce hygroscopicity and oxygen vacancies, results show that nitrogen helps suppress formation of the dielectric/Si-gate interlayer, thus enhancing gate screening effect on the remote phonon scattering to improve carrier mobility.

Comparing the planar and porous Nb-doped TiO2 photoanode of triple cation perovskite solar cells

Achieving an optimal electron transport layer is an essential step toward fabricating perovskite solar cells with higher power conversion efficiency (PCE). Photoanode and perovskite absorber are among the most influential components which affect the charge generation and transport rates. Here, we report on the photoanode modification and its influence on the triple cation perovskite solar cells. We successfully synthesized and systematically characterized the niobium (Nb) doping into the planar and mesoporous TiO2 electron transport layer. X-ray diffraction patterns, energy-dispersive X-ray spectroscopy maps, together with the optoelectronic measurements, prove higher Nb incorporation efficiency into the planar TiO2 photoanode. Electrochemical impedance spectroscopy, photocurrent density-voltage (J-V), and photoluminescence spectroscopy (PL) confirm that the charge transfer resistance of the photoanodes, transparency, and their dopant density have a considerable influence on the photocurrent generation and collection rates of the PSCs. Owing to the more visible light transmittance, greater charge transfer conductivity, and higher Nb incorporation efficiency, the planar photoanode demonstrates superior performance compared to the mesoporous counterpart. Moreover, J-V results exhibit substantial PCE improvement of 28.8 and 33.1% by the addition of 5 at.% Nb into the mesoporous and planar photoanodes, respectively, compared to the bare TiO2 photoanode. The radiative recombination rate within the perovskite absorber layer drops by Nb incorporation into the TiO2 photoanode, validated by the PL spectra. Remarkably, this radiative recombination quenches more in the planar photoanode, which is due to the lower charge transfer resistance of the planar TiO2 photoanodes.

Incorporating Nb into MoSe2 Nanoflowers for Overall Electrocatalytic Water Splitting

AbstractIncorporating transition metals such as by doping has a significant effect on the properties of TMDs, and it is an appealing research strategy to provide structural and functional tunability of these prospective materials for energy and environmental applications. Here we report the effect of incorporating Nb into MoSe2 nanoflowers on the catalytic properties for electrochemical water‐splitting. Impressively, the Nb incorporation greatly improved the active surface area and the charge‐transfer kinetics of the catalyst resulting in significant enhancement of the HER and OER activity. The considerable enhancement can be attributed to the synergistic effect of electronic regulation and surface modification induced by the Nb addition. The Nb‐modified MoSe2 comprise thin coverage of active Nb2O5 phase as evident from XPS. The niobium oxide is chemically stable under acidic and neutral conditions but degraded in strong alkaline media, thus our catalyst becomes a good candidate for water electrolysis under non‐alkaline conditions.

Quaternary-metal phosphide as electrocatalyst for efficient hydrogen evolution reaction in alkaline solution

Hydrogen evolution reaction (HER) is a critical process in electrocatalytic water splitting for hydrogen production. However, the development of low-cost electrocatalysts for highly efficient HER is still a huge challenge. Hence, we fabricate a multi-metal phosphide on Ni foam, FeCoNiNbxP, through a facile hydrothermal reaction followed by phosphorization. We find that Nb promotes the formation of metal phosphides, and the main phases of the catalysts with Nb are multiphase phosphides. Importantly, the Nb incorporation significantly improves the HER activity of FeCoNiP. We show that FeCoNiNb0.3P has the best HER activity, which only requires an overpotential of 78 mV to achieve a current density of 10 mA cm−2 in 1 M KOH, and demonstrates excellent stability under both constant potential and varied current densities. Our findings show that the multiple-metal compounds are beneficial to the improvement of catalytic activity and provide guidance on the design of novel catalysts for applications.

Nickel-Containing Ceria-Zirconia Doped with Ti and Nb. Effect of Support Composition and Preparation Method on Catalytic Activity in Methane Dry Reforming.

Nickel-containing mixed ceria-zirconia oxides also doped by Nb and Ti have been prepared by a citrate route and by original solvothermal continuous flow synthesis in supercritical alcohols. Nickel was subsequently deposited by conventional insipient wetness impregnation. The oxides are comprised of ceria-zirconia solid solution with cubic fluorite phase. Negligible amounts of impurities of zirconia are observed for samples prepared by citrate route and doped by Ti. Supports prepared by supercritical synthesis are single-phased. XRD data, Raman, and UV-Vis DR (diffuse reflectance) spectroscopy suggest increasing lattice parameter and amount of oxygen vacancies in fluorite structure after Nb and Ti incorporation despite of the preparation method. These structural changes correlate with the catalytic activity in a methane dry reforming reaction. Catalysts synthesized under supercritical conditions are more active than the catalysts of the same composition prepared by the citrate route. The catalytic activity of samples doped with Ti and Nb is two times higher in terms of TOF (turnover frequency) and increased stability of these catalysts is attributed with the highest oxygen mobility being crucial for gasification of coke precursors.

Disorder‐Induced Phonon Localization in Incipient Ferroelectric (Ni1/3Nb2/3)xTi1−xO2 Solid Solutions

The phonon behavior in incipient ferroelectric (Ni1/3Nb2/3)xTi1−xO2 ceramic solid solutions is investigated with combined Raman, Fourier transformed infrared (FTIR), and dielectric spectroscopy. The (Ni+Nb) incorporation into rutile TiO2 leads to the Raman and infrared modes broadening, the Gaussian‐type Raman peak of A2u(LO) mode, and the dielectric constant (at 14 K) of different compositions being proportional to the mole ratio of Ti cations. It suggests that, with increasing (Ni + Nb)‐substitution, the cationic disorder gradually develops and the disorder‐induced phonon localization occurs. In particular, the soft A2u mode appears to be localized to Ti‐containing regions. This work demonstrates that the combined Raman, FTIR, and dielectric analysis can effectively probe the cationic disorder and phonon localization behaviors in incipient ferroelectric (Ni1/3Nb2/3)xTi1−xO2 and provides an experimental evidence of phonon localization in 3D disordered systems with mass and spring constant disorder, which enriches the understanding of the Anderson localization in vibrational systems.

Platinum-catalyzed Nb–doped TiO2 and Nb-doped TiO2 nanotubes for hydrogen generation in proton exchange membrane water electrolyzers

This paper studies the catalytic activity of Pt deposited onto Nb-doped titania supports toward the hydrogen evolution reaction (HER). New catalysts based on Nb-doped TiO2 nanoparticles (nNb-TiO2) and Nb-doped TiO2 nanotubes (nNb-TNTs), with n in the range 3–10 at % (Nb + Ti), were synthesized. The specific surface areas of nNb-TNTs were 250–300 m2g-1, about three times higher than those of nNb-TiO2. X-ray diffraction showed the Nb incorporation into the TiO2 lattice with its consequent lattice expansion. The X-ray photoelectron spectra of Pt deposited onto Nb-doped titania revealed a negative charge accumulation on Pt, thus denoting strong metal-support interaction. The electrochemical characterization in acidic media showed that Pt supported on nNb-TiO2 and nNb-TNTs presented better activity toward the HER than that of Pt deposited onto the un-doped supports and commercial Pt on carbon. The best performance was obtained with a small Nb doping of 3 at %.