Preparation and photocatalytic activity of Ag/bamboo-type TiO2 nanotube composite electrodes for methylene blue degradation

Photocatalysis phenomena in TiO₂ have been intensively investigated for its potential application in environmental remediation. The present work reports improved photocatalytic degradation of methylene blue dye in aqueous solution by using bamboo-type TiO₂ nanotubes deposited with Ag nanoparticles via electrochemical deposition. The photocatalytic processes are performed on Ag-modified TiO₂ bamboo-type nanotube arrays, Ag-modified smooth-walled nanotube arrays, and bare smooth-walled nanotube arrays. Both Ag-modified bamboo-type and smooth-walled nanotube arrays show improved photocatalytic degradation efficiencies (64.4% and 52.6%) compared to smooth-walled TiO₂ nanotubes of the same length (44.4%), due to the enhanced electron–hole seperation and more surface area provided by bamboo ridges. The photocatalytic activity and kinetic behavior of Ag-modified bamboo-type nanotube arrays are also optmized by tuning pulse deposition time of Ag nanoparticles. Bamboo-type nanotubes deposited with Ag nanoparticles via pulse deposition time of 0.5 s/1.5 s shows the highest methylene blue degradation efficiency of 78.5%, which represents 21.9% and 76.8% enhancement of efficiency compared to those of bare bamboo-type and smooth-walled nanotubes, respectively, indicating that a proper amount of Ag nanoparticles on TiO₂ can maximize the photocatalytic processes. In addition, overly long pulse deposition time will not further increase photocatalytic activity due to agglomeration of Ag paticles. For example, when the pulse deposition time is increased to 2 s/6 s, Ag-modified bamboo-type nanotube array exhibits a lower photocatalytic degradation efficiency of 62.9%.     

Copper-incorporated titania nanotubes for effective lead ion removal

Small copper (Cu²⁺) dopant levels were successfully diffused into titanium dioxide (titania or TiO₂) nanotube lattice via an incipient wet impregnation technique. This study investigated the optimum Cu²⁺ dopant content to be incorporated into the TiO₂ nanotubes to achieve an effective lead ion (Pb(II)) removal system. The exciton states of the PL intensities varied in the following order: pure TiO₂>0.6 M Cu–TiO₂>0.1 M Cu–TiO₂>0.06 M Cu–TiO₂>0.01 M Cu–TiO₂. The significant quenching of the PL intensity indicates that incorporation of the appropriate amount of Cu²⁺ dopants into the TiO₂ lattice markedly enhanced the charge-carrier separation and transport. The photocatalytic ability of the samples was evaluated by the removal of the Pb(II) ions under UV illumination. The results show that the Cu dopants in the TiO₂ lattice at the optimum concentration (0.8 at%) acted as photoinduced electron mediators and thus increased the Pb(II) ion removal efficiency. The maximum Pb(II) ion removal rates for the 0.01 M Cu–TiO₂ nanotubes and after five hours of UV illumination were approximately 56.3% and 79.5% at pH 5 and pH 11, respectively. The generation of strong oxidizing agents (OH radicals) effectively reduces the toxic Pb(II) ions into PbO/PbOH.     

Low temperature synthesis of pure anatase carbon doped titanium dioxide: An efficient visible light active photocatalyst

Low temperature pure anatase Carbon Doped Titanium Dioxide (C-TiO₂) is successfully synthesized by using starch as an effective, economical, and nonhazardous carbon source. The synthesized C-TiO₂ has been further characterized by X-Ray Diffraction, SEM, TEM, BET, XPS and UV- DRS techniques, which reveal that the particles are crystalline with spherical morphology, high surface area and an optical band gap of 2.79 eV for C-TiO₂ calcined at 400 °C. Furthermore photocatalytic degradation of Rhodamine B dye was carried out using as-prepared C-TiO₂ under visible light irradiation. Prepared C-TiO₂ calcined at 200 °C and 400 °C show higher degradation efficiency (85% and 100% in 120 min respectively) as compared to that of undoped TiO₂ and commercial Degussa P-25. Result shows that the C-TiO₂ containing lower carbon percentage has higher photocatalytic activity. Thus enhanced photocatalytic activity of C-TiO_2, may be due to synergic effect of carbon doping and [101] facet enhanced synthesis of anatase C-TiO₂.     

Zero-valent nanophase iron and nitrogen co-modified titania nanotube arrays: Synthesis,characterization, and enhanced visible-light photocatalytic performance

We prepared nano-zero-valent iron (nZVI) and N co-modified TiO₂ (nZVI/N–TiO₂) nanotube arrays as an enhanced visible-light photocatalyst. The TiO₂ nanotube arrays were synthesized by electrochemical anodization of Ti foil in a two-electrode system. Amorphous TiO₂ nanotube arrays were immersed in ammonia and then annealed to produce crystalline N-doped TiO₂ (N–TiO₂) nanotube arrays. nZVI spheres were directly deposited on the N–TiO₂ nanotube arrays by borohydride reduction. The photocatalysts were characterized by field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), UV–visible diffuse reflectance spectroscopy (UV–vis DRS), and electrochemical impedance spectroscopy (EIS). The environmental applicability and photocatalytic activity of the proposed nZVI/N–TiO₂ nanotube arrays were tested by phenol degradation in an aqueous system under UV and visible light irradiation. The phenol degradation rate constants of each sample under visible light irradiation were in the following order: nZVI/N–TiO₂ (k_obs=0.006 min⁻¹⁾>N–TiO₂ (k_obs=0.002 min⁻¹) ⪢ nZVI/TiO₂ (k_obs=0.0003 min⁻¹)>TiO₂ (k_obs=0.0001 min⁻¹). This result can be attributed to the synergistic effect of the N–TiO₂ nanotubes with lower energy band gap and the electron transfer from the conduction band (CB) of N–TiO₂ to nZVI spheres highly-dispersed on the N–TiO₂ for enhanced separation of photogenerated electrons and holes.     

Rapid synthesis of TiO2/MWCNTs nanocatalyst with enhanced photocatalytic activity using modified microwave technique

This work described the rapid synthesis procedure for TiO₂/MWCNT nanocatalyst using a modified microwave method. Transmission electron micrographs suggested TiO₂ nanoparticles were strongly attached to the MWCNT. The surface area of the nanocatalysts determined by the Brunauer–Emmett–Teller method proved that the hybrid nanocatalyst have higher surface area (262.3 m²/g) than pristine TiO₂ (172.3 m²/g). The photocatalytic activity of the nanocatalyst was investigated under visible light (VL) illumination by studying the degradation of methylene blue dye (MB) with concentration of 10 ppm in 100 mL H₂O as a model compound. The results showed that the degradation efficiency obtained by using TiO₂/MWCNTs is about 40% higher than bare TiO₂. This signification enhancement was attributed to higher surface area and the ability of MWCNTs to act as a visible-light photosensitising agent revealing potential application in the treatment of wastewater.     

Synthesis of TiO2 thin films with highly efficient surfaces using a sol–gel technique

Three different strong acid catalysts were used in a simple sol–gel synthesis to produce TiO₂ thin films with increased homogeneity and enhanced photocatalytic activity on their mesoporous surfaces. Various techniques were used to characterize the samples, including UV–visible spectrophotometry, X-ray diffraction, micro-Raman spectrometry, photobleaching, scanning electron microscopy, transmission electron microscopy and high-resolution transmission electron microscopy. The band gaps varied from 3.73 to 3.75 eV and the transmittance was >80%. An anatase phase was obtained in all the samples and the crystal size varied from 20 to 45 nm as a function of the annealing temperature. The increase in the efficiency of the surface of the TiO₂ thin films was evaluated by photodegradation of methylene blue in water. The results showed that the acid catalysts used in the synthesis had an important effect on the morphology and photocatalytic activity of the thin films, resulting in more efficient surfaces. Synthesis with hydrofluoric acid produced thin films with a homogenous mesoporous structure and improved the photodegradation of the methylene blue dye to 92% in 2.5 h.     

Effects of silver substrates on the visible light photocatalytic activities of copper-doped titanium dioxide thin films

Novel copper-doped titanium dioxide (Cu-doped TiO₂) thin films on silver (Ag) substrates with different thicknesses were prepared by sol–gel and magnetron sputtering methods. The influences of the Ag substrate thickness on the morphology and performance of the films were investigated by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, UV–visible spectroscopy, and photocatalytic degradation testing with methylene blue aqueous solution under visible light irradiation. The results indicated that Ag substrates with an optimal thickness of 30 nm not only maintained the tiny nanocrystals but also greatly improved dispersion of the nanoparticles on the surface of the nanofilms. Furthermore, during the calcination process, part of the Ag atoms diffused from the substrates into the Cu–TiO₂ films and substituted for the Cu ions to form Ag–TiO₂. A proper Ag substrate thickness (30 nm) greatly improved the photocatalytic properties of TiO₂ with photocatalytic efficiency, reaching approximately 86% in 300 minutes under visible light irradiation. However, an excess of Ag substrate not only led to the Cu ion separating out in the form of CuO but also resulted in the agglomeration of TiO₂ particles on the surface, which were detrimental to photocatalytic activities.     

Visible-light-driven composite La2O3/TiO2 nanotube arrays: Synthesis and improved photocatalytic activity

In this work, using a lanthanum nitrate solution as lanthanum source, a visible-light responsive La₂O₃/TiO₂ nanotube arrays (TNTs) composite was synthesized by a facile impregnation-calcinations technique. The as-synthesized samples were characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectroscopy and photocurrent tests. The photocatalytic activity of the La₂O₃/TNTs composite under visible-light irradiation (λ>420 nm) was evaluated by the degradation of Rhodamine B (RhB). The results revealed one part of La was doped, and the other part was dispersed on the TNTs surface in the form of La₂O₃. La-doping narrowed the band gap and La₂O₃ modification accelerated the separation of photo-induced electron-hole pairs. Consequently, the as-prepared La₂O₃/TNTs composite exhibited much higher photocatalytic activity than pure TNTs. The photocatalytic activity of the composite was related to impregnation time of lanthanum nitrate solution, and an optimal time was 2 h. The activity of 2-La₂O₃/TNTs displayed 3.7 times as high as that of pure TNTs. A possible mechanism on the La₂O₃/TNTs photocatalytic activities is suggested. The composite, as promising materials, could be used to degrade dye wastewater or other organic pollutants.     

WO3/TiO2 nanocomposites: Salt–ultrasonic assisted hydrothermal synthesis and enhanced photocatalytic activity

A series of WO₃/TiO₂ composite photocatalysts were fabricated via a facile salt–ultrasonic assisted hydrothermal process. The obtained samples were characterized by X-ray diffraction, scanning eletron microscopy, energy dispersive X-ray spectroscopy and UV–vis diffused reflectance spectroscopy. It was confirmed that anatase TiO₂ and monoclinic WO₃ coexisted in the composites. The photocatalytic activity of as-prepared WO₃/TiO₂ composites for degradation of Rhodamin B (RhB) under visible light irradiation was investigated. The results showed that WO₃/TiO₂ composites have a higher photocatalytic activity than those of pure TiO₂ and pure WO₃. First-principle calculations based on density functional theory were performed to explore the electronic structure and illustrate the photocatalytic mechanism of WO₃/TiO₂. The calculated energy gap was 2.53 eV, which was close to the experimental observation (2.58 eV). Due to the combination of WO₃/TiO₂, the photoinduced electrons and holes transfer between the WO₃ and TiO₂ in opposite directions, thus providing sufficient charge separation, which contributed to the photocatalytic activity enhancement.     

Effect of seed layer on the growth of rutile TiO2 nanorod arrays and their performance in dye-sensitized solar cells

In order to improve the performance of TiO₂ photoanode-based dye sensitized solar cells (DSSCs), rutile TiO₂ nanorod arrays (NRAs) were grown on SnO₂:F (FTO) conductive glass coated with TiO₂ seed layer by a hydrothermal method. The TiO₂ seed layer was obtained by spin-coating titanium tetraisopropoxide (TTIP) isopropanol solution with concentration in the range of 0~0.075 M. Then the effect of the thin TiO₂ seed layer on the crystal structure and surface morphology of TiO₂ NRAs and the photoelectric conversion properties of the corresponding DSSCs were investigated. It is found that TiO₂ NRAs are vertically oriented, about 1.7 μm long and the average diameter is about 35 nm for the samples derived from TTIP in the range of 0.005~0.05 M, which are more uniform and better separated from each other than those without TiO₂ seed layer (average diameter 35~85 nm). The photoelectric conversion efficiency of DSSCs based on TiO₂ NRAs with TiO₂ seed layer is larger than that without TiO₂ seed layer. Typically, the energy efficiency of DSSCs obtained from the seed solution of 0.025 M TTIP is 1.47%, about 1.8 times greater than that without TiO₂ seed layer. The performance improvement is attributed to the thinner, denser and better oriented NRAs grown on seeded-FTO substrate absorbing more dye and suppressing charge recombination at the FTO substrate/electrolyte interface.     

Solar photocatalytic activity of chemical solution-prepared barium tungstate nanostructures

Nanostructured barium tungstate (BaWO₄) as a solar photocatalyst has been successfully synthesized by a chemical solution method. The sample was characterized using X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and UV–vis diffuse reflectance spectroscopy. Then, the photocatalytic degradation of methylene blue (MB) in an aqueous medium was evaluated with nanostructured BaWO₄ under direct sunlight irradiation. The effects of the initial pH, and the catalyst dosage on the dye degradation were studied in order to achieve maximum degradation efficiency. The nanostructured BaWO₄ exhibited good photocatalytic activity for degradation of MB under sunlight irradiation at pH 10 after 3 h of irradiation. Also, the optimal catalyst loading of 25 mg/L obtained throughout the present study. The degradation of the dye followed the first-order reaction and the adsorption obeyed the Langmuir model.     

Enhanced photocatalytic performance of platinized CdS/TiO2 by optimizing calcination temperature of TiO2 nanotubes

TiO₂ nanotubes were prepared by hydrothermal treatment of TiO₂ powder in NaOH aqueous solution and then calcined at various temperatures. The post-calcination treated TiO₂ nanotubes were decorated with CdS by wetness impregnation and subsequently sulfurization to fabricate CdS/TiO₂ composites. The photocatalytic performance of CdS/TiO₂ composites toward hydrogen production from water splitting was investigated. The results show that the calcination temperature of TiO₂ nanotubes has a significant effect on the photocatalytic performance of CdS/TiO₂. With the increase of calcination temperature from 300 to 500 °C, the crystallinity of TiO₂ nanotubes is increased resulting in the enhanced photocatalytic performance of CdS/TiO₂. When the calcination temperature is higher than 500 °C, TiO₂ nanotubes gradually transform into nanorods and finally completely collapse, which leads to the decrease of photocatalytic performance of CdS/TiO₂. The CdS/TiO₂ composite with TiO₂ nanotubes calcined at 500 °C exhibits the highest hydrogen evolution rate, which could be attributed to its 1 D nanotubular structure and good crystallinity.     

Photocatalytic activity of TiO2/Ti composite coatings fabricated by mechanical coating technique and subsequent heat oxidation

Titanium (Ti) coatings were fabricated on alumina (Al₂O₃) balls by mechanical coating technique (MCT) with Ti powder. The Ti coatings were then oxidized to titanium dioxide (TiO₂) coatings at different temperatures. The oxidation behavior and microstructure evolution of these coatings were investigated. The results showed that the inner and surface layers of the Ti coatings were oxidized simultaneously. When oxidizing at a relatively low temperature for a short time, TiO₂/Ti composite coatings were obtained. Increasing the oxidation temperature or time increased the thickness of the TiO₂ layer and eventually Ti coatings were totally oxidized to TiO₂ coatings. During oxidation, TiO₂ needles formed at a lower temperature grew to generate columnar crystals. The photocatalytic activity of these coatings was examined. Compared with TiO₂ coatings, the TiO₂/Ti composite coatings showed much higher photocatalytic activity. The highest activity was observed for the TiO₂/Ti composite coatings prepared by MCT and subsequent oxidation at 1073 K for 15 h and then the thickness of the TiO₂ layer was 27 μm.     

The relation between TiO2 nano-pastes rheology and dye sensitized solar cell photoanode efficiency

TiO₂ nanoparticle pastes for screen printed semiconductive photoanodes of dye sensitized solar cells were prepared with different content (from 0 to 9 wt%) of ethyl cellulose and evaluated by rheology measurements. The effect of ethyl cellulose content in the paste is crucial for printed and sintered TiO₂ photoanode properties as thickness, roughness and amount of adsorbed dye, measured by profilometry, atomic force microscopy, IR and UV‐Vis spectroscopy. Moreover, the expressive correlation among paste rheology, layer properties and the final dye sensitized solar cell efficiency depending on the initial ethyl cellulose content was found, including correlations of the properties local maxima positions. The highest efficiency was achieved for the TiO₂ paste with 6.5 wt% of ethyl cellulose, where initial paste viscosity and thixotropy, printed layer thickness, roughness and amount of adsorbed dye achieved the local maxima (~40 Pa.s, 4.5 µm, 24 nm, 1.92×10⁻⁸ mol/cm², respectively) that indicates the optimal structure of the oxide photoanode layer. The results confirm the importance of controlled ethyl cellulose concentration and rheological properties of applied pastes for higher DSSC efficiency achievement.     

Mesoporous-assembled In2O3–TiO2 mixed oxide photocatalysts for efficient degradation of azo dye contaminant in aqueous solution

This work focuses on the improvement of the photocatalytic activity of mesoporous-assembled In₂O₃–TiO₂ mixed oxide photocatalysts for Congo Red (CR) azo dye degradation by varying the In₂O₃-to-TiO₂ molar ratio and calcination temperature. All of photocatalysts are synthesized by a sol–gel process with the aid of a structure-directing surfactant. The results show that the incorporation of In₂O₃ to the mesoporous-assembled TiO₂ can increase the specific surface area and total pore volume, inhibit the anatase-to-rutile phase transformation, and decrease the crystallite size of the resulting In₂O₃–TiO₂ mixed oxide photocatalysts. The mesoporous-assembled 0.05In₂O₃–0.95TiO₂ mixed oxide photocatalyst with an In₂O₃-to-TiO₂ molar ratio of 0.05:0.95 (5 mol% In₂O₃ incorporation) and calcined at 500 °C exhibits the highest CR dye degradation activity (with reaction rate constant of 0.86 h⁻¹), being considerably higher than that of the commercial P-25 TiO₂ powder.     

Sol–gel-synthesized mesoporous-assembled TiO2–ZrO2 mixed oxide nanocrystals and their photocatalytic sensitized H2 production activity under visible light irradiation

The purpose of this work was to investigate, in the first study of its kind, hydrogen production by photocatalytic water splitting under visible light irradiation using Eosin Y-sensitized mesoporous-assembled TiO₂–ZrO₂ mixed oxide nanocrystal photocatalysts. The mesoporous-assembled TiO₂–ZrO₂ mixed oxide nanocrystals, with various TiO₂-to-ZrO₂ molar ratios, were synthesized by a sol–gel method with the aid of a structure-directing surfactant. The synthesized nanocrystals were characterized by thermogravimetric and derivative thermogravimetric analyzer, N₂ adsorption–desorption, X-ray diffraction, UV–visible spectroscopy, scanning electron microscope–energy-dispersive X-ray analyzer, and transmission electron microscope analyses. Parameters affecting the photocatalytic activity, including calcination conditions and phase composition, were mainly discussed. Experimental results showed that the incorporation of ZrO₂ with suitable contents could preserve the mesoporous-assembled structure of TiO₂ at high calcination temperatures and enhance its thermal stability significantly. Results of the photocatalytic-sensitized hydrogen production revealed that the TiO₂–ZrO₂ mixed oxide photocatalyst, with a TiO₂-to-ZrO₂ molar ratio of 95:5, calcined at 800 °C for 4 h, provided maximum photocatalytic hydrogen production activity. The optimized TiO₂–ZrO₂ mixed oxide photocatalyst can be considered as a potential photocatalyst for hydrogen production under solar light irradiation.     

Facile synthesis of monodispersed nanocrystalline anatase TiO2 particles with large surface area and enhanced photocatalytic activity for degradation of organic contaminant in wastewaters

Monodispersed nanocrystalline anatase TiO₂ particles have been successfully synthesized via a facile hydrothermal process, combined with encircling hexamethylenetetramine protectors. The products are characterized in detail by X-ray diffraction, Raman spectra, and transmission electron microscope. Experimental results indicate that the catalysts possess monodispersed nanocrystalline anatase structure with small particles (∼6 nm) and large surface area (286 m² g⁻¹), which are attributed to encircling hexamethylenetetramine protectors for inhibiting the undesirable grain growth. The obtained monodispersed nanocrystalline anatase TiO₂ particles exhibit better photocatalytic activity than that of Degussa P25 TiO₂ for degradation of highly toxic 2,4-dichlorophenol in wastewaters under UV irradiation, which is ascribed to the small particle size and large surface area offering more active sites, and the improved crystallinity in favor of the separation of photogenerated electron–hole pairs.     

Binder-free MWCNT/TiO2 multilayer nanocomposite as an efficient thin interfacial layer for photoanode of dye sensitized solar cell

Multiwalled carbon nanotube/TiO₂ multilayer nanocomposite was successfully deposited on the fluorine-doped tin oxide (FTO) glass via layer-by-layer assembly technique to modify interfacial contact between the FTO surface and nanocrystalline TiO₂ layer as well as carbon nanotube/TiO₂ contacts in photoanode of dye sensitized solar cell. Using this approach, binder-free interfacial thin film was developed with nonagglomerated, well-dispersed MWCNTs on FTO and into TiO₂ matrix and with maximum covering of TiO₂ nanoparticles on MWCNTs. Introduction of MWCNTs/TiO₂ interfacial layer into the TiO₂ photoanode increased short circuit current density (J_sc) from 11.90 to 17.25 mA/cm² and open circuit voltage (V_oc) from 730 mV to 755 mV, whereas there was no notable change in the fill factor (FF). Consequently, power conversion efficiency (η) was enhanced from 5.32% to 7.53%, yielding a 41.5% enhancement. The results suggest that our simple strategy can integrate reduction of back electron reaction at FTO/TiO₂ interface with the effective charge transport ability of carbon nanotubes and possessing high surface area for efficient dye loading.     

Preparation and characterization of TiO2 thin film by thermal oxidation of sputtered Ti film

Titanium dioxide (TiO₂) thin films were successfully prepared on quartz substrate by thermal oxidation of sputtered titanium film in air. The structure, composition, morphology and optical properties of oxidized TiO₂ films were characterized by Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscopy and UV-visible spectroscopy. Meanwhile, the photocatalytic activity of the films was evaluated on the basis of the degradation of methyl orange solution under UV irradiation. Ti films after oxidation present mainly in TiO₂ form with a larger amount of adsorbed O₂, and oxidation temperature has a strong impact on the crystal structure and properties of the films. A phase transformation of anatase to rutile for oxidized TiO₂ films occurred in the temperature range of 700–800 °C. The energy band gap of oxidized TiO₂ films decreased first and then increased with annealing temperature. Furthermore, TiO₂ film oxidized at 600 °C exhibited the best photocatalytic activity due to suitable crystal phase and size. These results might contribute to the synthesis of metal oxide thin films with expectant structural morphology and properties by thermal oxidation methods.     

Synthesis of Sn doped ZnO/TiO2 nanocomposite film and their application to H2 gas sensing properties

Tin doped Zinc oxide/Titanium oxide nanocomposite (TZO/TiO₂) was prepared by two methods: TiO₂ nanotube (Nt) arrays are grown by anodic oxidation of titanium foil and TZO films was deposited on the TiO₂ Nt obtained by hydrothermal process. The morphological characteristics and structures of ZnO/TiO₂ and TZO/TiO₂ were examined by (scanning elecron miscroscopy) SEM, (X rays diffraction) XRD and (energy dispersive spectroscopy) EDS analysis. The diameter of TiO₂ Nts was ranged from 40 nm to 90 nm with wall thicknesses of approximately 10 nm. The anatase structure of Titania, the hexagonal Zincite crystal of zinc oxide and tetragonal structure of tin oxide were identified by XRD. EDS analysis revealed the presence of O, Zn, Ti and Sn elements in the obtained deposits.These nanocomposites have been used as active layer in hydrogen gas sensing application. The hydrogen sensing characteristics of the sensor was analyzed by measuring the sensor responses in the temperature of 100 °C and 160 °C. The highest gas response is approximately 1.48 at 160 °C.The sensing mechanism of the nanocomposite sensor was explained in terms of H₂ chimisorption on the highly active nanotube surface.