Preparation and characterization of Ni-doped TiO2 materials for photocurrent and photocatalytic applications

Remarkable photocatalytic performances towards pollutant degradation under sunlight and enhanced electrochemical properties of TiO2/polymer nanohybrids

In this work, TiO₂-based nanocomposites containing polyaniline (PANI), poly(1-naphthylamine) (PNA), and polyindole (PIN) were synthesized by effective and simple routes and posteriorly employed as photocatalysts and supercapacitors. Characterization techniques such as XRD, FTIR, FESEM, UV, and PL were employed to investigate the structural, morphological, and optical properties of materials. XRD analysis confirmed the successful formation of TiO₂ and TiO₂/polymer nanocomposites. PANI, PNA, and PIN polymers were well distributed on the surface of TiO₂ nanoparticles and were investigated/explored from the FESEM analysis. The visible light absorption and the recombination rate of photogenerated charge carriers were confirmed by the UV-Vis and PL analysis. The photocatalytic properties of the nanocomposites were investigated towards malachite green (MG) dye degradation under sunlight. The dye degradation efficiency followed the order TiO₂/PNA > TiO₂/PANI > TiO₂ > TiO₂/PIN. The higher efficiency of TiO₂/PNA can be associated with its smaller bandgap energy compared to the other materials. Electrochemical properties of materials were also examined by cyclic voltammetry and galvanostatic charge-discharge measurements using a three-electrode experiment setup in an aqueous electrolyte. TiO₂/PNA nanocomposite showed higher supercapacitor behavior compared to the other materials due to higher electrical conductivity of PNA and redox potential of TiO₂ (pseudocapacitance).

Structure and Photocatalytic Properties of Ni-, Co-, Cu-, and Fe-Doped TiO2 Aerogels

TiO₂ aerogels doped with Ni, Co, Cu, and Fe were prepared, and their structure and photocatalytic activity during the decomposition of a model pollutant, acid orange (AO7), were studied. After calcination at 500 °C and 900 °C, the structure and composition of the doped aerogels were evaluated and analyzed. XRD analysis revealed the presence of anatase/brookite and rutile phases in the aerogels along with other oxide phases from the dopants. SEM and TEM microscopy showed the nanostructure of the aerogels, and BET analysis showed their mesoporosity and high specific surface area of 130 to 160 m²·g^-1. SEM-EDS, STEM-EDS, XPS, EPR methods and FTIR analysis evaluated the presence of dopants and their chemical state. The concentration of doped metals in aerogels varied from 1 to 5 wt.%. The photocatalytic activity was evaluated using UV spectrophotometry and photodegradation of the AO7 pollutant. Ni-TiO₂ and Cu-TiO₂ aerogels calcined at 500 °C showed higher photoactivity coefficients (k_aap) than aerogels calcined at 900 °C, which were ten times less active due to the transformation of anatase and brookite to the rutile phase and the loss of textural properties of the aerogels.

Efficient NiO/F-TiO2 nanocomposites for 4-chlorophenol photodegradation

This work aimed to study NiO/F-TiO₂ composites in the photocatalytic degradation of 4-chlorophenol. F-TiO₂ support was prepared by in-situ fluorination of TiO₂ using the sol-gel method. The heterostructured materials were prepared by wet impregnation method, varying NiO content (0.5, 1.0, and 2.0% wt). The solids were characterized by X-ray fluorescence, X-ray diffraction, nitrogen physisorption, diffuse reflectance UV-Vis spectrophotometry, infrared spectroscopy, and X-ray photoelectron spectroscopy. The characterization studies showed that the coupling of TiO₂ with fluoride ions promoted the generation of ≡Ti-F surface species that could be responsible for the decrease in the recombination frequency of charge carriers and the increased photoactivity. In addition, it was found that the coupling of NiO/F-TiO₂ semiconductors improved the photocatalytic properties of the fluorinated support, obtaining higher percentages of degradation and mineralization of the phenolic contaminant. These results are possibly a consequence of factors such as the formation of larger crystallites, lower band gap energies, and the generation of p-n type interfacial heterojunctions that potentiate the proper separation of electron-hole pairs. An effect of NiO content on photoactivity was observed, being a percentage of 1.0% wt the optimum in this photocatalytic treatment.

Partially Reduced Ni-NiO-TiO2 Photocatalysts for Hydrogen Production from Methanol–Water Solution

The study compares the photocatalytic behavior of TiO2, NiO-TiO2, and Ni-NiO-TiO2 photocatalysts in photocatalytic hydrogen production from methanol–water solution. TiO2 and NiO-TiO2 photocatalysts with theoretical NiO loading of 0.5, 1.0, and 3.0 wt. % of NiO were prepared by the sol–gel method. The Ni-NiO-TiO2 photocatalysts were prepared by partial reduction of NiO-TiO2 in hydrogen at 450 °C. The Ni-NiO-TiO2 photocatalysts showed significantly higher hydrogen production than the NiO-TiO2 photocatalysts. The structural, textural, redox, and optical properties of all of the prepared photocatalysts were studied by using XRD, SEM, N2- adsorption, XPS, H2-TPR, and DRS. Attention is focused on the contribution of Ni loading, the surface composition (Ni2+, the lattice O2− species, and OH groups), the distribution of Ni species (dispersed NiO species, crystalline NiO phase, and the metallic Ni0 species), oxygen vacancies, TiO2 modification, the TiO2 crystallite size, and the specific surface area.

Photocatalytic Degradation of Organic Dyes Contaminated Aqueous Solution Using Binary CdTiO2 and Ternary NiCdTiO2 Nanocomposites

The synergistic effect of binary CdTiO2 and ternary NiCdTiO2 on the photocatalytic efficiency of TiO2 nanoparticles was investigated. The SEM analysis demonstrates spherical TiO2 NPs of different sizes present in agglomerated form. The structural analysis of the nanocomposites reveals a porous structure for TiO2 with well deposited Cd and Ni NPs. TEM images show NiCdTiO2 nanocomposites as highly crystalline particles having spherical and cubical geometry with an average particle size of 20 nm. The EDX and XRD analysis confirm the purity and anatase phase of TiO2, respectively. Physical features of NiCdTiO2 nanocomposite were determined via BET analysis which shows that the surface area, pore size and pore volume are 61.2 m2/g, 10.6 nm and 0.1 cm3/g, respectively. The absorbance wavelengths of the CdTiO2 and NiCdTiO2 nanocomposites have shown red shift as compared to the neat TiO2 due to coupling with Ni and Cd that results in the enhanced photocatalytic activity. The photocatalytic activity demonstrated that TiO2, CdTiO2 and NiCdTiO2 degrade methylene blue (MB) and methyl green (MG) about 76.59, 82, 86% and 63.5, 88, 97.5%, respectively, at optimum reaction conditions.

Efficient photocatalytic degradation of nitrobenzene by copper-doped TiO2: kinetic study, degradation pathway, and mechanism

Cu-doped TiO2 (0.1, 0.25, and 0.5% Cu-TiO2) photocatalyst was prepared by sol-gel method and was characterized by powder XRD, FTIR, TEM, SEM, EDX, UV-vis diffuse reflectance (DRS), photoluminescence (PL), and Raman spectroscopy. The XRD spectrum shows tetragonal anatase phase. TEM analysis indicate that the nanoparticles were spherical with sizes 12-13 nm. The degradation of NB was studied, and an optimal degradation time of 180 min led to 98.6% NB abatement of NB = 0.05 mM, pH = 4, and catalyst loading = 50 mg/100 mL, under visible light. The degradation of NB follows the pseudo-first-order kinetics. The reusability studies indicated the excellent stability of 0.25% Cu-TiO2.

Enhanced Fe-TiO2 Solar Photocatalysts on Porous Platforms for Water Purification

In this study, polyethylene glycol-modified titanium dioxide (PEG-modified TiO2) nanopowders were prepared using a fast solvothermal method under microwave irradiation, and without any further calcination processes. These nanopowders were further impregnated on porous polymeric platforms by drop-casting. The effect of adding iron with different molar ratios (1, 2, and 5%) of iron precursor was investigated. The characterization of the produced materials was carried out by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Optical characterization of all the materials was also carried out. SEM showed that pure TiO2 and Fe-TiO2 nanostructures presented similar nanosized and spherical particles, which uniformly covered the substrates. From XRD, pure TiO2 anatase was obtained for all nanopowders produced, which was further confirmed by Raman spectroscopy on the impregnated substrates. XPS and UV-VIS absorption spectroscopy emission spectra revealed that the presence of Fe ions on the Fe-TiO2 nanostructures led to the introduction of new intermediate energy levels, as well as defects that contributed to an enhancement in the photocatalytic performance. The photocatalytic results under solar radiation demonstrated increased photocatalytic activity in the presence of the 5% Fe-TiO2 nanostructures (Rhodamine B degradation of 85% after 3.5 h, compared to 74% with pure TiO2 for the same exposure time). The photodegradation rate of RhB dye with the Fe-TiO2 substrate was 1.5-times faster than pure TiO2. Reusability tests were also performed. The approach developed in this work originated novel functionalized photocatalytic platforms, which were revealed to be promising for the removal of organic dyes from wastewater.

Floating Carbon-Doped TiO2 Photocatalyst with Metallic Underlayers Investigation for Polluted Water Treatment under Visible-Light Irradiation

In the current study, we analysed the influence of metallic underlayers on carbon-doped TiO2 films for RhB decomposition and Salmonella typhimurium inactivation under visible-light irradiation. All the experiments were divided into two parts. First, layered M/C-doped-TiO2 film structures (M = Ni, Nb, Cu) were prepared by magnetron sputtering technique on borosilicate glass substrates in the two-step deposition process. The influence of metal underlayer on the formation of the carbon-doped TiO2 films was characterised by X-ray diffractometer, scanning electron microscope, and atomic force microscope. The comparison between the visible-light assisted photocatalytic activity of M/C-doped TiO2 structures was performed by the photocatalytic bleaching tests of Rhodamine B dye aqueous solution. The best photocatalytic performance was observed for Ni/C-doped-TiO2 film combination. During the second part of the study, the Ni/C-doped-TiO2 film combination was deposited on high-density polyethylene beads which were selected as a floating substrate. The morphology and surface chemical analyses of the floating photocatalyst were performed. The viability and membrane permeability of Salmonella typhimurium were tested in cycling experiments under UV-B and visible-light irradiation. Three consecutive photocatalytic treatments of fresh bacteria suspensions with the same set of floating photocatalyst showed promising results, as after the third 1 h-long treatment bacteria viability was still reduced by 90% and 50% for UV-B and visible-light irradiation, respectively. The membrane permeability and ethidium fluorescence results suggest that Ni underlayer might have direct and indirect effect on the bacteria inactivation process. Additionally, relatively low loss of the photocatalyst efficiency suggests that floating C-doped TiO2 photocatalyst with the Ni underlayer might be seen as the possible solution for the used photocatalyst recovery issue.

Photocatalytic Degradation of Thiacloprid Using Tri-Doped TiO2 Photocatalysts: A Preliminary Comparative Study

Different tri-doped TiO2 photocatalysts (Fe-N-P/TiO2, Fe-N-S/TiO2, Fe-Pr-N/TiO2, Pr-N-S/TiO2, and P-N-S/TiO2) were successfully prepared and tested in the photocatalytic removal of thiacloprid (THI) under UV-A, visible, and direct solar light irradiation. The physical-chemical properties of the prepared catalysts were analyzed by different characterization techniques, revealing that dopants are effectively incorporated into the anatase TiO2 lattice, resulting in a decrease of the energy band gap. The reduction of photoluminescence intensity indicates a lower combination rate and longer lifespan of photogenerated carriers of all doped samples in comparison with the un-doped TiO2. The doped photocatalysts not only significantly promote the photodegradation under UV-A light irradiation but also extend the optical response of TiO2 to visible light region, and consequently improve the visible light degradation of THI. Fe-N-P tri-doped TiO2 sample exhibits the highest THI photodegradation degree (64% under UV-A light, 29% under visible light and 73% under solar light).

Enhancing Lithium and Sodium Storage Properties of TiO2(B) Nanobelts by Doping with Nickel and Zinc

Nickel- and zinc-doped TiO2(B) nanobelts were synthesized using a hydrothermal technique. It was found that the incorporation of 5 at.% Ni into bronze TiO2 expanded the unit cell by 4%. Furthermore, Ni dopant induced the 3d energy levels within TiO2(B) band structure and oxygen defects, narrowing the band gap from 3.28 eV (undoped) to 2.70 eV. Oppositely, Zn entered restrictedly into TiO2(B), but nonetheless, improves its electronic properties (Eg is narrowed to 3.21 eV). The conductivity of nickel- (2.24 × 10-8 S·cm-1) and zinc-containing (3.29 × 10-9 S·cm-1) TiO2(B) exceeds that of unmodified TiO2(B) (1.05 × 10-10 S·cm-1). When tested for electrochemical storage, nickel-doped mesoporous TiO2(B) nanobelts exhibited improved electrochemical performance. For lithium batteries, a reversible capacity of 173 mAh·g-1 was reached after 100 cycles at the current load of 50 mA·g-1, whereas, for unmodified and Zn-doped samples, around 140 and 151 mAh·g-1 was obtained. Moreover, Ni doping enhanced the rate capability of TiO2(B) nanobelts (104 mAh·g-1 at a current density of 1.8 A·g-1). In terms of sodium storage, nickel-doped TiO2(B) nanobelts exhibited improved cycling with a stabilized reversible capacity of 97 mAh·g-1 over 50 cycles at the current load of 35 mA·g-1.

Nickel and sulfur codoped TiO2 nanoparticles for efficient visible light photocatalytic activity

In this work, Nickel (Ni) and sulfur (S) codoped TiO2 nanoparticles were prepared by a sol-gel technique. The as-prepared catalyst was characterized using X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), FT-Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectra (DRS) for investigating crystal structure, crystal phase, particle size and bandgap energy of these samples. The photocatalytic performances of all the prepared catalysts have been investigated for the degradation of methylene blue (MB) under visible light irradiation. It was noticed that Ni-S codoped TiO2(Ni-S/TiO2) nanoparticles exhibited much higher photocatalytic activity compared with pure, Ni and S doped TiO2 due to higher visible light absorption and probable decrease in the recombination of photo-generated charges. It was decided that the great visible light absorption was created for codoped TiO2 by the formation of impurity energy states near both the edges of the collection, which works as trapping sites for both the photogenerated charges to decrease the recombination process.

Unravelling the interfacial interaction in mesoporous SiO2@nickel phyllosilicate/TiO2 core-shell nanostructures for photocatalytic activity

Core-shell based nanostructures are attractive candidates for photocatalysis owing to their tunable physicochemical properties, their interfacial contact effects, and their efficacy in charge-carrier separation. This study reports, for the first time, on the synthesis of mesoporous silica@nickel phyllosilicate/titania (mSiO₂@NiPS/TiO₂) core-shell nanostructures. The TEM results showed that the mSiO₂@NiPS composite has a core-shell nanostructure with a unique flake-like shell morphology. XPS analysis revealed the successful formation of 1:1 nickel phyllosilicate on the SiO₂ surface. The addition of TiO₂ to the mSiO₂@NiPS yielded the mSiO₂@NiPS/TiO₂ composite. The bandgap energy of mSiO₂@NiPS and of mSiO₂@NiPS/TiO₂ were estimated to be 2.05 and 2.68 eV, respectively, indicating the role of titania in tuning the optoelectronic properties of the SiO₂@nickel phyllosilicate. As a proof of concept, the core-shell nanostructures were used as photocatalysts for the degradation of methyl violet dye and the degradation efficiencies were found to be 72% and 99% for the mSiO₂@NiPS and the mSiO₂@NiPS/TiO₂ nanostructures, respectively. Furthermore, a recyclability test revealed good stability and recyclability of the mSiO₂@NiPS/TiO₂ photocatalyst with a degradation efficacy of 93% after three cycles. The porous flake-like morphology of the nickel phyllosilicate acted as a suitable support for the TiO₂ nanoparticles. Further, a coating of TiO₂ on the mSiO₂@NiPS surface greatly affected the surface features and optoelectronic properties of the core-shell nanostructure and yielded superior photocatalytic properties.

Origin of the enhanced photocatalytic activity of (Ni, Se, and B) mono- and co-doped anatase TiO2 materials under visible light: a hybrid DFT study

The characteristic properties of TiO₂ (anatase) make doping necessary to enhance its photocatalytic activity. Herein, a density functional theory (DFT) study using the Heyd–Scuseria–Ernzerhof (HSE) hybrid functional was performed to precisely investigate the effect of mono- and co-doping (Ni, Se and B) on the structural, electronic and optical properties of anatase TiO₂. Notably, the origin of the enhanced photocatalytic activity of the modified systems was determined. The response to visible light was enhanced for all the mono- and co-doped materials except for B_int, and the highest absorption coefficient was observed for Se⁴⁺ mono-doping and Se/B_int+sub and Ni/B_sub co-doping. The decrease in bandgap is associated with a red shift in the absorption edges with the smallest bandgap calculated for Ni/B_sub (2.49 eV). Additionally, the Ni, Se⁴⁺ and Se²⁻ mono-doped systems and Ni/Se⁴⁺ co-doped systems are proposed as promising photocatalysts for water splitting applications and further experimental validation. Moreover, the Ni/B_int+sub and Se/B_int+sub co-doped materials can also be valuable photocatalysts for other energy applications due to their enhanced visible light activity and the prolonged lifetime of their produced charge carriers.

Hybrid DFT calculations demonstrate that Ni, Se⁴⁺ and Se²⁻ mono-doped and Ni/Se⁴⁺ co-doped TiO₂ are potential photocatalysts for water splitting and hydrogen production.

High-Temperature Hydrogen Sensing Performance of Ni-Doped TiO2 Prepared by Co-Precipitation Method

This work deals with the substantially high-temperature hydrogen sensors required by combustion and processing technologies. It reports the synthesis of undoped and Ni-doped TiO2 (with 0, 0.5, 1 and 2 mol.% of Ni) nanoparticles by a co-precipitation method and the obtained characteristics applicable for this purpose. The effect of nickel doping on the morphological variation, as well as on the phase transition from anatase to rutile, of TiO2 was investigated by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. The resistive sensors prepared with these powders were tested toward H2 at 600 °C. The results indicate that 0.5% Ni-doped TiO2 with almost equal amounts of anatase and rutile shows the best H2 sensor response (ΔR/R0 = 72%), response rate and selectivity. The significant improvement of the sensing performance of 0.5% Ni-doped TiO2 is mainly attributed to the formation of the highest number of n-n junctions present between anatase and rutile, which influence the quantity of adsorbed oxygen (i.e., the active reaction site) on the surface and the conductivity of the material.

Bi3TaO7/Ti3C2 heterojunctions for enhanced photocatalytic removal of water-borne contaminants

Novel catalysts are of great interest for improved photocatalytic environmental remediation. Using a hydrothermal method, 0D/2D Bi₃TaO₇/Ti₃C₂ heterojunctions were designed rationally and characterized systematically as excellent photocatalysts for photocatalytic degradation. The hybrid catalyst exhibits superior performance in visible-light-driven photocatalytic degradation of methylene blue (about 99% degradation efficiency after 2 h) and excellent stability (up to 10 cycles) under visible light irradiation (300 W Xe lamp; λ > 420 nm; light intensity 150 mW cm^-2). In addition, Bi₃TaO₇/Ti₃C₂ has a larger rate constant (0.032 min^-1) than pristine Bi₃TaO₇ (0.006 min^-1). Quantum yield (2.27 × 10^-5 molecules/photon) and figure of merit (23.3) of the system were obtained, suggesting that our catalyst has potential for application. Both experimental and computational results indicate that synergistic effects between Bi₃TaO₇ and Ti₃C₂ improve photocatalytic performance by enhancing electron-hole pair separation, electronic transmission efficiency, and interfacial charge transfer. These findings contribute to the synthesis of efficient visible-light-driven Bi-based photocatalysts and to the understanding of photocatalytic degradation reactions.

Effects of Fe and Ni Co-Doping on the Optical Properties of TiO2 Thin Films

In this work, the effects of Fe/Ni co-doping on structural and optical properties of TiO2 thin films were investigated by the X-ray diffraction, scanning electron microscope and UV-visible spectroscopy. The optical properties of transmittance, extinction coefficient, refractive index, real and imaginary parts of dielectric constant of the thin films, prepared by spray pyrolysis, revealed that the absorption in visible region increases due to the influence of Fe/Ni co-doping. The widening of the gap energies is observed as a result of doping. The increased optical gap as a consequence of doping can be explained by decreasing the size of nanoparticles, as confirmed by SEM and increasing the formation of oxygen vacancies as a result of Ni[Formula: see text] substitution to Ti[Formula: see text] and appearance of the Burstein–Moss effect.

Ni-doped and Ni/Cr co-doped TiO2 nanotubes for enhancement of photocatalytic degradation of methylene blue

Ni-doped and Ni/Cr co-doped TiO₂ nanotubes were successfully synthesized using a novel hydrothermal method. The surface and bulk properties of as-synthesized nanopowders were characterized using various microstructural and optical techniques. The photocatalytic ability of these nanopowders was investigated systematically for the decomposition of methylene blue dye (MB) under visible light illumination. The morphological results revealed the structural transformation of TiO₂ nanotubes to nanosheets, and further to a mixture of nanosheet/nanotube on doping with Ni and co-doping of Ni/Cr, respectively. Moreover, the Ni doping causes an optical absorption edge shifts towards lower wavelengths, while doping by Ni/Cr results to an optical absorption edge shifts towards higher wavelength in comparison to TiO₂-nanotubes. Also, Ni-doping and Ni/Cr co-doping strongly affects the Raman vibrational modes owing to the changes in interplanar distance, crystallite size, dislocation density, and crystal microstrains. Among the undoped, doped and co-doped TiO₂ nanoparticles, the 6Ni/4Cr co-doped TiO₂ exhibited a higher efficiency of 95.6% and excellent stability towards the photocatalytic degradation of MB. It is attributed to the availability of many carriers for the efficient photo-oxidation within the UV-Vis optical absorption range. Also, the photocatalytic reaction kinetics and degradation mechanism of MB were discussed.

KSCN-induced Interfacial Dipole in Black TiO2 for Enhanced Photocatalytic CO2 Reduction

Tuning the electronic band structure of black titania to improve photocatalytic performance through conventional band engineering methods has been challenging because of the defect-induced charge carrier and trapping sites. In this study, KSCN-modified hydrogenated nickel nanocluster-modified black TiO₂ (SCN-H-Ni-TiO₂) exhibits enhanced photocatalytic CO₂ reduction due to the interfacial dipole effect. Upon combining the experimental and theoretical simulation approach, the presence of an electrostatic interfacial dipole associated with chemisorption of SCN has dramatic effects on the photocatalyst band structure in SCN-H-Ni-TiO₂. An interfacial dipole possesses a more negative zeta potential shift of the isoelectric point from 5.20 to 3.20, which will accelerate the charge carrier separation and electron transfer process. Thiocyanate ion passivation on black TiO₂ demonstrated an increased work function around 0.60 eV, which was induced by the interracial dipole effect. Overall, the SCN-H-Ni-TiO₂ photocatalyst showed an enhanced CO₂ reduction to solar fuel yield by 2.80 times higher than H-Ni-TiO₂ and retained around 88% product formation yield after 40 h.

Enhanced Photocatalytic Degradation of Organic Dyes via Defect-Rich TiO2 Prepared by Dielectric Barrier Discharge Plasma

The dye wastewater produced in the printing and dyeing industry causes serious harm to the natural environment. TiO₂ usually shows photocatalytic degradation of dye under the irradiation ultravilet light rather than visible light. In this work, a large number of oxygen vacancies and Ti³⁺ defects were generated on the surface of the TiO₂ nanoparticles via Ar plasma. Compared with pristine TiO₂ nanoparticles, the as-obtained Ar plasma-treated TiO₂ (Ar-TiO₂) nanoparticles make the energy band gap reduce from 3.21 eV to 3.17 eV and exhibit enhanced photocatalytic degradation of organic dyes. The Ar-TiO₂ obtained exhibited excellent degradation properties of methyl orange (MO); the degradation rate under sunlight irradiation was 99.6% in 30 min, and the photocatalytic performance was about twice that of the original TiO₂ nanoparticles (49%). The degradation rate under visible light (λ > 400 nm) irradiation was 89% in 150 min, and the photocatalytic performance of the Ar-TiO₂ was approaching ~4 times higher than that of the original TiO₂ nanoparticles (23%). Ar-TiO₂ also showed good degradation performance in degrading rhodamine B (Rho B) and methylene blue (MB). We believe that this plasma strategy provides a new method for improving the photocatalytic activity of other metal oxides.

Structural, optical and magnetic behavior of sol–gel derived Ni-doped dilute magnetic semiconductor TiO2 nanocrystals for advanced functional applications

Defect engineering of Ni-doped TiO₂ could tailor the magnetic properties through BMP interactions, which is advantageous for spintronics applications.

Investigation of the influence of vanadium, iron and nickel dopants on the morphology, and crystal structure and photocatalytic properties of titanium dioxide based nanopowders

Photoactive V, Fe and Ni doped TiO2 (M-TiO2) nanopowders were synthesized by a modified two-step sol-gel process in the absence of additives. Titanium oxychloride, which is a rarely-used TiO2 precursor was used to yield M-TiO2 photocatalysts with preferential photochemical performance in the presence of natural solar irradiation. The obtained samples were calcined at different calcination temperatures ranging from 450 to 800°C to evaluate the influence of the sintering on the physicochemical properties. The properties of the obtained samples were examined by XRF, XRD, Raman spectroscopy, UV-visible DRS, XPS, nitrogen gas physisorption studies, SEM-EDAX and HRTEM analyses. Structural characterization of the samples revealed the incorporation of these transition metal element into TiO2. It was also depicted that the morphology, crystal structure, optical and photochemical properties of the obtained samples were largely dependent on the calcination temperature and the type of dopant used during the preparation process. The photochemical performance of the samples was investigated in the photodegradation of methylene blue in the presence of natural sunlight. The experimental results indicated that the VT600 sample possessed the highest activity due to its superior properties. This study provides a systematic preparation and selection of the precursor, dopant and calcination temperature that are suitable for the formation of TiO2-based heterogeneous photocatalysts with appealing morphology, crystal structure, optical and photochemical properties for myriad of applications.

Enhanced visible light absorption and photocatalytic activity of [KNbO3]1−x[BaNi0.5Nb0.5O3−δ]x synthesized by sol–gel based Pechini method

[KNbO₃]_1−x[BaNi_0.5Nb_0.5O_3−δ]_x were synthesized by Pechini sol–gel method at low temperature. Visible light photocatalytic performance of this material was evaluated.

Rapid and morphology controlled synthesis of anionic S-doped TiO2 photocatalysts for the visible-light-driven photodegradation of organic pollutants

In recent years, growing concerned has been raised to the global problem of the drainage of organic pollutants into water steams.

Photocatalytic H2 generation over In2TiO5, Ni substituted In2TiO5 and NiTiO3 – a combined theoretical and experimental study

Role of Ni substitution in modifying the crystal structure, optical absorption properties and electronic properties of indium titanate, In_2(1−x)Ni_2xTiO_5−δ (0.0 ≤ 2x ≤ 0.4) and its consequent effect on the photocatalytic properties for H₂ generation.

Visible-light photocatalytic activity of nitrogen-doped NiTiO3 thin films prepared by a co-sputtering process

NiTiO₃ thin films grown using a co-sputtering process exhibited well defined structural, morphological and optical characteristics, which showed enhanced visible light photocatalytic activity.

Effect of Calcination Temperature on Synthesis of N-Fe-TiO2 for Photocatalytic Degradation of Methylene Blue under Visible Light

Effect of calcination temperature on the synthesis of N, Fe codoped TiO2 for the photodegradation of methylene blue under ordinary visible lamps was investigated. The photocatalyst were prepared using solgel method where titanium isopropoxide was used as precursor of titania. The calcination temperatures were varied from 450 to 600°C. The prepared photocatalysts were characterized by using XRD, FE-SEM and FTIR to determine their physical properties. The results from XRD proved that photocatalysts calcined at 600°C possessed perfect properties in phase and crystal size. FE-SEM image analysis revealed the formation of the fine spherical particles and the FTIR analysis verified the presence of dopants at various calcination temperatures. The effectivity of photocatalysts was tested by performing a standard batch photocatalytic degradation experiment with methylene blue as a model pollutant under ordinary visible light. The result showed that N and Fe codoped photocatalyst calcined at 600°C (1.0 % N, Fe-TiO2-600) yielded a maximum of 80.50% methylene blue degraded within five hours of irradiation time.

Ni-doped TiO2 nanotubes for wide-range hydrogen sensing

Doping of titania nanotubes is one of the efficient way to obtain improved physical and chemical properties. Through electrochemical anodization and annealing treatment, Ni-doped TiO2 nanotube arrays were fabricated and their hydrogen sensing performance was investigated. The nanotube sensor demonstrated a good sensitivity for wide-range detection of both dilute and high-concentration hydrogen atmospheres ranging from 50 ppm to 2% H2. A temperature-dependent sensing from 25°C to 200°C was also found. Based on the experimental measurements and first-principles calculations, the electronic structure and hydrogen sensing properties of the Ni-doped TiO2 with an anatase structure were also investigated. It reveals that Ni substitution of the Ti sites could induce significant inversion of the conductivity type and effective reduction of the bandgap of anatase oxide. The calculations also reveal that the resistance change for Ni-doped anatase TiO2 with/without hydrogen absorption was closely related to the bandgap especially the Ni-induced impurity level.