Nb2O5 Nanoparticles Research Articles

Needle growth of Nb2O5 nanoparticles on BiOCl nanosheets to fabricate S-scheme heterojunction with oxygen vacancies for enhanced photooxidation of cyclohexane

The exploration of cost-efficient, environmentally friendly, and high-efficacy photocatalysts for the enhanced selective photooxidation of cyclohexane to KA oil (cyclohexanone (CHA-one) and cyclohexanol (CHA-ol)) is a pivotal challenge in the industrial realm. Herein, the present study focuses on the synthesis of needle-like S-scheme heterojunction photocatalysts with oxygen vacancies, which are achieved by the needle growth integration of nano-sized Nb2O5 particles onto the BiOCl nanosheets. Remarkably, the 40 % Nb2O5/BiOCl composites exhibited superior performance in the solvent-free photooxidation of cyclohexane at room-temperature and under atmospheric pressure. The production yield of KA oil was 180.3 μmol (CHA-one/CHA-ol molar ratio = 3.5), and exceptional selectivity towards KA oil, reaching up to 99.3 %. The enhanced photocatalytic efficiency in cyclohexane oxidation can be attributed to the unique S-scheme heterogeneous interfaces with specific nanoneedle morphology, which result in the enhanced photonic absorption, effective charge carrier separation, a high density of oxygen vacancies, and the exposure of the highly reactive (001) plane of BiOCl. The excellent interfacial charge separation and transfer pathways of S-scheme heterojunction are disclosed by the in-depth EPR analysis and DFT calculations. These insights highlight the significant potential of the needle-like Bi-based S-scheme heterojunction photocatalysts for the efficient photooxidation of saturated alkanes.

Sphere-like Nb2O5 nanoparticles by waste Brassica oleracea leaf extract for lead removal and photocatalytic degradation of methylene blue dye

Currently, water-soluble pollutants such as hazardous chemicals and pigments create severe environmental hazards. Heavy metals such as lead, chromium, mercury, and arsenic were dangerous to living beings even at very low levels. To overcome this limitation, Nb2O5 nanoparticles were created utilizing a novel green approach. Based on plant components, green technique is a low-cost, safe, and environmentally good solution. In the present inquiry, we employ phytonutrients from waste Brassica oleracea leaf juice as a capping and reducing component. The product was evaluated using XRD, FT-IR, UV, SEM, and TEM techniques. The findings showed that the produced Nb2O5 NPs had a sphere-like geometry having a median particle dimension of 9 nm confirmed by XRD analysis. SEM study reveals ultrafine, homogeneous morphological agglomerations and uniform granules in TEM analysis, 10–15 nm particles predicted by crystallography, orthorhombic Nb2O5 (001) planes matching 0.39 nm lattice edge measurement error, and a clearly defined SAED diffract signal implying polycrystalline calcined powder. Excitation absorbance bands at 350 nm may be caused by charged balancing in the Nb–O–Nb architecture increasing oxygen concentration confirmed by UV–Vis analysis. The Nb2O5 nanosphere has a surface area of 120 m2/g, 0.592 cm2/g of pores, and a mean pore dimension of 15.2 nm, determined using Barrett-Joyner-Halenda (BJH). A sequential Adsorption capacities assay shown that it is an effective absorber used to eliminate Pb (II) ions from aqueous solutions. Adsorbents was able to be readily removed from the resultant fluid and recycled repeatedly. The produced Nb2O5 Nanoparticles are capable of removing toxic heavy metals and synthetic colors from polluted waterways.

Enhancing Fracture Toughness of Dental Zirconia through Incorporation of Nb into the Surface.

Our previous study found that the addition of pentavalent cations like niobium (Nb) to yttria-stabilized zirconia increased fracture toughness but also raised the coefficient of thermal expansion (CTE), and opacity also increased undesirably. A new surface treatment is required to boost fracture toughness without altering CTE or translucency. The surfaces of pre-sintered 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) and 4.2 mol% yttria-stabilized partially stabilized zirconia (4.2Y-PSZ) were treated with a Nb sol solution containing Nb2O5 nanoparticles. After drying and sintering, a high-Nb-content surface layer formed with a depth of approximately 1 mm. The Nb content in this surface layer matched that of a bulk material with 1 mol% Nb2O5. The tetragonality of the surface zirconia increased, enhancing the surface fracture toughness without changing the CTE or translucency. Adding Nb near the surface improved the fracture toughness without affecting the CTE or translucency. This method could strengthen zirconia prostheses, allowing more reliable dental restorations.

Efficient photocatalytic hydrogen evolution by in situ construction of Nb4+ charge-carrier channels in hollow porous tubular C3N4 and Nb2O5 Z-scheme heterojunctions

Optimizing heterojunction structure is an important way to improve photocatalytic activity. Herein, we report a novel hollow tubular C3N4/Nb4+/Nb2O5 nanoparticle Z-Scheme heterojunction, by introducing Nb4+ ions into Nb2O5 through a reducing atmosphere during C3N4 thermal polymerization. The optimized heterostructure showed outstanding photocatalytic hydrogen evolution activity under both UV–vis (14.93 mmol g−1 h−1) and Vis (5.22 mmol g−1 h−1) lights. The photocatalytic hydrogen evolution activity under UV–vis light is 26.6 and 4.75 times that of bulk C3N4 (CN) and hollow tubular C3N4 (HCN), respectively. The increased photocatalytic activity can be attributed to the larger specific surface area, more active sites, and enhanced light absorption capacity of the composite. Crucially, the introduction of Nb4+ ions as the charge-carrier transport channels in the Z-scheme heterostructure improves the efficiency of photogenerated charge-carrier separation. This study provides a useful design strategy for Z-Scheme photocatalytic heterojunction structures that can utilize solar light more efficiently.

Tailoring the graphene framework by embedding Nb2O5 and silver nanoparticles for electrodes in energy storage applications

In this study, Nb2O5/GNs and Ag/GNs-based nanocomposites were synthesized via a facile single-step hydrothermal approach. Using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, fourier-transform infrared (FTIR) spectroscopy, and UV–vis spectroscopy, the morphology, functional groups, structure, and optical and electrical properties of the as-prepared materials were examined. XPS studies show the predominant signal at 284.8 eV is attributed to the sp2 carbon atoms (C 1) that comprise graphitic areas, indicating that the majority of the C atoms are arranged in a honeycomb lattice. FTIR spectrum confirms bonding, such as CO, CH2, CO, CC, OH, AgO, and NbONb in the nanocomposite. Further, the specific capacitance (Csp) of the Nb2O5/GNs and Ag/GNs was calculated 603 Fg−1 and 810 Fg−1 at different current densities, The Nb2O5/GNs exhibit 109 Wh/kg and 2180 W/kg energy and power density, respectively. However, the Ag/GNs electrode exhibited an energy density of 145.8 Wh/kg and a power density of 3645 W/kg, with cyclic stability retentions of 93.06 % and 97.02 %, respectively. The capacitance retention finished at 1000 cycles. Moreover, the achieved resistance from the I–V characteristics curve shows enhanced electrical conductivity of synthesized nanocomposites. These results suggested that the materials can have bright future in next-generation energy storage devices.

Manipulating oxygen vacancy for controlling the kinetics of Nb2O5-based anode in Li-ion capacitor

Introducing appropriate oxygen vacancies (OVs) improves the integral conductivity of the Nb2O5 anode of Li-ion capacitors (LICs). Whereas a few recent studies link the OVs level and the kinetics of Nb2O5, the quantitative relationship between the OVs and the performance of Nb2O5 remains elusive. Herein, we show that the OVs concentration in Nb2O5 can be quantitatively manipulated by regulating the oxygen content in niobium complex (NbL) precursors, thus controlling the kinetics of the Nb2O5-based anode. The OVs concentration is inversely proportional to the oxygen content in the NbL, where it facilitates the electronic transfer and the Li-ion migration of Nb2O5 with optimal introduction. In addition, the ligand in the NbL can also be used as a sacrificial template for creating an N-doped carbon coating wrapping Nb2O5 nanoparticles with OVs to further improve the electronic conductivity of the composite. This was followed by depositing the NbL nanoparticles via electrophoretic deposition for assembling binder-free electrodes. The integrated electrode-based LICs deliver 76 μWh cm−2 at 550 μW cm−2 and retain 94 % of the capacity after 5000 cycles. This work provides a new recognition for the design of metal oxide electrodes with fast kinetics for LICs from material modification to electrode material assembly.

Synthesis and characterization of polypyrrole/graphitic carbon nitride/niobium pentoxide nanocomposite for high‐performance energy storage applications

AbstractGraphitic carbon nitride (GCN) has been employed as a supercapacitor electrode because of its high carbon‐to‐nitrogen ratio and flexible structure. However, its low surface area and poor conductivity continue to be obstacles for practical usage. GCN's electrochemical characteristics are enhanced by the hybrid structure it forms with polypyrrole and Nb2O5. The synthesized polypyrrole (Ppy)/GCN/niobium pentoxide (Nb2O5) (Ppy/GCN/Nb2O5) nanocomposite electrode was tested for supercapacitance by cyclic voltammetry (CV) and Alternating current impedance techniques in 6 M Potassium hydroxide(KOH) electrolyte. The Ppy/GCN/Nb2O5 is linked to a network of agglomerated GCN and Nb2O5 nanoparticles with additional spherical shapes. The specific capacitance of Ppy/GCN/Nb2O5 was determined to be 1177 Fg−1 at a current density of 5 Ag−1. The Ppy/GCN/Nb2O5 electrode in KOH has average specific energy and specific power densities of 33 Wh kg−1 and 2991 W kg−1, respectively. The electrode showed excellent capacitance‐retention ability of 97% after 10,000 cycles. The results demonstrate the high stability and efficient performance of the Ppy/GCN/Nb2O5 electrode employed in supercapacitors. The performance of the Ppy/GCN/Nb2O5 electrode was found to be superior to those reported for other carbon‐based materials.

Evidence of oxygen vacancy-mediated ultrahigh SERS sensitivity of Niobium pentoxide nanoparticles through defect engineering: theoretical and experimental studies.

Oxygen vacancy engineering in metal oxide-based semiconductors has emerged as an important area of research for sensing applications, such as Surface-enhanced Raman scattering (SERS), gas sensing, etc. It has the potential to replace high-cost and unstable noble metal-based substrates in the near future. However, improving the SERS enhancement factor in semiconductor-based substrates remains a challenge. In the present study, we demonstrate that oxygen vacancy engineering in Niobium pentoxide (Nb2O5) enables ultrahigh SERS sensitivity. Oxygen vacancies were induced and manipulated in the Nb2O5 nanoparticles via a facile high-energy ball milling method and post-growth oxygen annealing. A high enhancement factor (EF) of 5.15 × 107 was obtained for the Methylene Blue (MeB) molecule on the oxygen-deficient substrate with the lowest detection limit of 10-8 M, which is 2 orders of magnitude lower than the pristine substrate. Through a careful analysis of the experimental data and theoretical calculations, we investigated the underlying mechanism behind the high EF in SERS and showed that the SERS performance is directly proportional to the oxygen vacancy concentration in the Nb2O5 nanoparticles. Density functional theory (DFT) calculation suggests a strong coupling of the vibronic states and an increased charge transfer (CT) efficiency in the Nb2O5-MeB complex mediated through the vacancy-induced trap states in the defective Nb2O5 structure. Finite element method (FEM)-based simulations revealed a field enhancement factor of ∼4.17 × 102 that contributed to the SERS EF, while the remaining is contributed to the oxygen vacancy-mediated charge transfer, i.e., a factor of ∼1.23 × 105 is due to the high CT efficiency, the highest among the reported values. We believe that these findings offer valuable insights into the fabrication of defect-tailored cost-effective semiconductor-based SERS substrates for ensuing applications, such as trace dye detection.

Organofunctionalized Nb2O5 Nanoparticles for Photodynamic Therapy against A549 Cancer Cells

Niobium pentoxide shows an interesting reactivity that allows the control of different aspects of its morphology and chemistry. In this study, Nb2O5 nanoparticles were modified with protoporphyrin IX (PPIX) and tris(ethynylphenyl) pyrene derivative (PyPh3) by using 3-aminopropyltriethoxysilane as linkage group and used as photosensitizers against lung cancer. The antitumor photoactivity against the A549 tumor cell line as a model of in vitro study showed half maximal inhibitory concentration (IC50) ca. 15 μmol L-1 for both materials and the absence of dark activity, indicating the viability of dye-modified Nb2O5 as a photodynamic therapy (PDT) agent.

Single-Step Formation of Metal Oxide Nanostructures Wrapped in Mesoporous Silica and Silica–Niobia Catalysts for the Condensation of Furfural with Acetone

The integration of metal oxide nanomaterials with mesoporous silica is a promising approach to exploiting the advantages of both types of materials. Traditional synthesis methods typically require multiple steps. This work instead presents a fast, one-step, template-free method for the synthesis of metal oxides homogeneously dispersed within mesoporous silica, including oxides of W, Ti, Nb, Ta, Sn, and Mo. These composites have tunable metal oxide contents, large surface areas, and wide mesopores. The combination of Nb2O5 nanoparticles (NPs) with SiO2 results in an increased surface area and a larger number of acid sites compared to pure Nb2O5 NPs. The surface texture and acidity of the silica–niobia composites can be tuned by adjusting the Nb/Si molar ratio. Moreover, the silica provides protection to the niobia NPs, preventing sintering during thermal treatment at 400 °C. The silica–niobia materials exhibit superior performance as catalysts in the aldol condensation of furfural (Fur) with acetone compared to pure niobia, leading to an up to 62% in product yield. Additionally, these catalysts show remarkable stability, retaining their performance over multiple runs. This work demonstrates the potential of the proposed synthesis approach for preparing more sustainable, high-performance, durable, and stable nanoscale metal oxide-based catalysts with a tunable composition, surface area, and active site density.

Structural and Interfacial Manipulation of Multifunctional Skeletons Enabled Shuttling-Free and Dendrite-Free Li-S Full Batteries.

Li-S batteries are regarded as promising devices for energy storage systems owing to high energy density, low cost, and environmental friendliness. However, challenges of polysulfides shuttling in sulfur cathode and dendrite growth of lithium anode severely hinder the practical application. Developing advanced skeletons simultaneously regulating the cathode and anode is significant and challenging. Hence, a novel and scalable strategy combining spray drying and topological nitriding is proposed, and hierarchically assembled rGO hollow microspheres encapsulated highly porous nanospheres consisted of ultrafine Nb4 N5 -Nb2 O5 or Nb4 N5 nanoparticles as multifunctional skeletons for S and Li are designed. In such unique architecture, a 3D highly porous structure provides abundant void space for loading of S and Li, and accommodates volume change during cycling. Moreover, Nb4 N5 -Nb2 O5 heterostructured interface promotes adsorption-conversion process of polysulfides, while strong lithophilic Nb4 N5 induces the selective infiltration of Li into the void of the skeleton and regulates the uniform deposition and growth. More interestingly, in situ generated Li3 N@Nb ion/electron conducting interfaces induced by the reaction of Nb4 N5 and Li reduce the nucleation overpotential and induce selective deposition of Li into the cavity. Consequently, the Li-S full cell exhibits superior cycling stability and impressive rate performance with a low capacity ratio of negative/positive.

Flexible N-doped carbon nanofiber containing Nb2O5 nanoparticle and its polydimethylsiloxane composite for electromagnetic interference shielding

The miniaturization of electronic devices and systems has led to increasingly sophisticated electronic circuits, resulting in electromagnetic interference (EMI) that can substantially influence performance of electronic devices and wireless communications. To address this issue, researchers have extensively explored various strategies including application of EMI shielding materials. Here, we use Nb2O5 nanoparticles incorporated N-doped carbon nanofibers (Nb2O5–CNF) for EMI shielding applications in wide frequency range (8.2 GHz–26.5 GHz). Nb2O5–CNF was prepared through electrospinning, followed by carbonization. A 50 wt% loading of Nb2O5 (Nb2O5–CNF-50) exhibited high EMI shielding effectiveness of 67 dB with a thickness of 0.08 mm, where, more than 80% of shielding is through absorption mechanism. Ease of handling of Nb2O5–CNF could be improved by making flexible PDMS composites of Nb2O5–CNF. The PDMS composites exhibited similar EMI shielding behavior in the frequency range 8.2–26.5 GHz. Nb2O5–CNF and their PDMS composites can open up new possibilities towards large scale production of lightweight, flexible, and easy-to-integrate materials to shield workspaces, surroundings, and complex electronic circuits against unwanted EM radiations.

Microwave radiation method for rapid synthesis of Nb2O5@MoS2 as high-performance supercapacitor electrode materials

Microwave irradiation was used to create Nb2O5/MoS2 nanocomposites. The composite was self-assembled from flaky MoS2 and Nb2O5 nanotubes, according to structural and performance studies. Cyclic voltammetry, the timed potential method, and electrochemical impedance spectroscopy were employed to investigate the electrochemical properties. The specific capacitance of Nb2O5/MoS2 nanocomposites (628 F/g) was greater than that of pure Nb2O5 nanoparticles (183 F/g) and MoS2 at a current density of 1 A/g (125 F/g). Cyclic properties confirmed that the nanocomposites had higher cyclic stability, with a capacitance retention rate of 90.6 % after 5000 cycles. Dynamic analysis revealed that large conductive networks ensured Nb2O5/MoS2 electrochemical performance. The specific capacitance of the Nb2O5/MoS2 composite has increased, allowing efficient transport of ions and charges across the electrode surface with electrolytes. According to electrochemical studies, Nb2O5/MoS2 nanocomposites have the potential to be effective electrodes for high-performance supercapacitor applications.

Acetone gas sensor based on Nb2O5 @SnO2 hybrid structure with high selectivity and ppt-level sensitivity

For air quality monitoring and medical diagnosis, the development of sensors for low-concentration acetone gas is desirable but challenging. In this study, Nb2O5 nanoparticles were loaded onto SnO2 nanosheets to build a hybrid structure with a loose structure as sensor materials. The spiky Nb2O5 (s-Nb2O5) exhibited a higher response for acetone detection than the Nb2O5 nanorods (r-Nb2O5). Gas sensors based on the s-Nb2O5 @SnO2 composite exhibited a remarkable enhancement in the acetone sensing-performance, with high response, a low detection limit, and good selectivity at 250 ℃. The response of the s-Nb2O5 @SnO2 composites to 500 ppb acetone was nearly 37, which was superior to that of the pure SnO2 nanosheets, with a response of 12; the experimental and theoretical limits of detection (LODs) were 40 ppt and 4.77 ppt, respectively. The present experimental and theoretical LODs are the lowest among those reported for gas sensors based on metal oxide semiconductors. The high response likely originates from the n-n heterostructure, synergistic effect, and the existence of a large amount of chemisorbed oxygen. Additionally, the loose structure played significant roles in the enhanced sensing performance. Such favorable acetone sensing performance endows these s-Nb2O5 @SnO2 heterostructures with potential applicability in ppt-level acetone gas detection.

Enhancement of Mechanical Behaviors and Microstructure Evolution of Nano-Nb2O5/AZ31 Composite Processed via Equal-Channel Angular Pressing (ECAP)

The automobile industry uses magnesium for load-bearing components due to its low density, durability, and ductility. This study investigated a nanocomposite containing Nb2O5 (3 and 6 wt%) nanoparticles as reinforcement with AZ31 magnesium alloy made by stir casting. A severe plastic deformation was conducted on the cast samples via equal-channel angular pressing (ECAP) after homogenization at 410 °C for 24 h and aging at 200 °C for 10 h. The microstructural distributions and mechanical properties of the magnesium metal matrix composites (MMCs) reinforced with Nb2O5 nanoparticles were investigated via ECAP. With the increase in the number of ECAP passes, the grain sizes became uniform, and the size of secondary phases reduced in the pure Nb2O5/AZ31 MMC. The grain size decreased remarkably after the ECAP process from 31.95 µm to 18.41µm due to the dynamic recrystallization during plastic deformation. The mechanical properties of hardness, ultimate tensile strength, and elongation effectively improved after each ECAP pass. The maximum values achieved for the Nb2O5/AZ31 composite subjected to ECAP were 64.12 ± 12 HV, 151.2 MPa, and 52.71%.

Dual-confinement effect in metal oxide nanoparticles/MXene-reduced graphene oxide for high capacitive deionization performance

Metal oxide nanoparticles are one kind of important electrode materials for capacitive deionization (CDI) application. Unfortunately, most metal oxide materials usually exhibit poor electrical conductivity and often experience slow dissolution of metallic species, thereby resulting in limited desalination performance. Overcoming these obstacles still remains challenging due to the lack of synthetic approaches. Taking it into consideration, herein we proposed a dual confinement strategy to promote the CDI application of metal oxide nanoparticles. Nb2O5 was synthesized as a typical example for designing metal oxide/MXene-reduced graphene oxide (rGO) derived from Nb2CTx MXene/graphene oxide (GO) under hydrothermal condition. In the hybrid, Nb2CTx and rGO serve as both the confinement agent and conductive support for Nb2O5 nanoparticles, endowing Nb2O5/Nb2CTx-rGO with improved electronic conductivity and structural stability. As a result, the hybrid shows an outstanding desalination performance, including a NaCl adsorption capacity of 41.07 mg g−1, an ultra-fast average NaCl adsorption rate of 4.14 mg g−1 min−1 and excellent long-term cycling stability of 50 cycles (81 % desalination capacity retention rate). This work is expected to bring new insights in the synthesis of metal oxide materials for electrochemical desalination.

The role of oxygen vacancies in TT-Nb2O5 nanoparticles for the photoconversion of glycerol into solketal

Defect engineering of Nb2O5 nanoparticles is an approachable way to improve photocatalytic performance. TT-Nb2O5 nanoparticles were synthesized using the Pechini method followed by calcination, producing line defects in the crystalline structure and single-electron-trapped oxygen vacancies (SETOVs). The structural results demonstrate that TT-Nb2O5 calcined at 500 °C presents a superlattice orthorhombic structure with a specific surface area between 45 and 90 m2 g−1 and mesoporous network structure. Electronic properties analysis revealed that the TT-Nb2O5 nanoparticles synthesized by the Pechini method (NbPEG and NbEG) have different concentrations of SETOVs in their structure according to the polymerizing agent used in the synthesis, ethylene glycol and polyethylene glycol for NbEG and NbPEG, respectively. The unprecedented photochemical acetalization of glycerol into solketal, employing isopropyl alcohol instead of acetone, was described. The textural properties and the higher concentration of SETOVs significantly improved the photocatalytic performance of NbEG, allowing a synergistic dual catalytic behavior, where the electron accumulation process on the surface of the semiconductor took place, inducing proton generation, which improved the conversion of glycerol (47.8%) as well as the selectivity to solketal (69.8%).

Probing the interaction between niobium pentoxide nanoparticles and serum albumin proteins by Spectroscopic approaches

Nanoparticles (NPs) can directly or indirectly enter into the body because of their small size; then they tend to alter the conformation and function of proteins upon interaction with them. Thus, it is crucial to understand the impact of NPs in a biological medium. Recently, niobium pentoxide nanoparticles (Nb2O5 NPs) are finding increasing applications in the biological system, for example, bone tissue and dental material, matrix for biosensing of proteins, etc. In all such applications, the Nb2O5 NP interacts with proteins and other biomolecules. Hence, the study of such interactions is of considerable importance. Here in this work, we present the impact of Nb2O5 NP on the structure, stability and activity of blood proteins, bovine serum albumin (BSA) and human serum albumin (HSA) by means of various spectroscopic approaches. Steady-state fluorescence studies indicated that intrinsic fluorescence intensities of both serum albumin proteins got quenched upon their interaction with NP. The nature of the quenching was elucidated by time-resolved fluorescence and absorption measurements. Using circular dichroism (CD) and synchronous fluorescence spectroscopy (SFS), the structural perturbations of the protein molecules after interaction with NP were investigated. Moreover, the role of temperature on protein stability upon complexation with NP was also explored. In addition, the effect of NP on protein functionality was probed by esterase-like activity assays. Communicated by Ramaswamy H. Sarma

Green Synthesis of Nb2O5 Nanoparticles and Photodegradation of Remazol Yellow RR Dye

Synthesis of nanoparticles by the recently developed green approach is extremely promising because of its non-toxicity and environmentally friendly nature. In present investigation, Nb2O5 nanoparticles were prepared by environmental friendly way from niobium ethaoxide using Aloe Vera leaf pulp. The synthesis of Nb2O5 nanoparticles was confirmed by systematic characterization using XRD, EDX, Brunauer–Emmett–Teller (BET) surface area measurements and FTIR studies. The removal efficiency of Remazol yellow RR dye over the as synthesized Nb2O5 nanoparticles as a photocatalyst was determined along with emphasizing on the parameters of initial dye concentration, catalyst loading and pH. For the photocatalytic degradation of Remazol yellow RR dye solutions pH was varied in the range of 2 to 9. For the optimization, the maximum decolorization of 95 % was observed in 120 min for low initial dye concentration of 30 mg/L for 1.5 g/L of Nb2O5 photocatalyst. Besides, the effects of oxidant species and scavengers were studied systematically.

Predicting the catalytic performance of Nb-doped nickel oxide catalysts for the oxidative dehydrogenation of ethane by knowing their electrochemical properties

In the present article, a relationship between the catalytic performance in the oxidative dehydrogenation of ethane (ODHE) for Nb-doped NiO catalysts and their electrochemical properties has been proposed. To do so, highly stable and selective Nb-doped NiO catalysts for the ODHE to ethylene have been synthesized by optimizing synthesis parameters such as the amount of oxalic acid in the synthesis gel and the calcination temperature. These catalysts have been characterized by means of XRD, HRTEM, Raman and UV–vis diffuse reflectance spectroscopies, TPR and XPS. Moreover, Electrochemical Impedance Spectroscopy (EIS), capacitance measurements (Mott-Schottky analysis) and cyclic voltammetries studies were also carried out. Electrochemical characterization indicates changes in the type of semiconductivity: p-type for samples calcined at 350 °C and the sample prepared in the absence of oxalic acid and calcined at 500 °C, to n-type for samples prepared in the presence of oxalic acid in the synthesis gel and calcined at 500 °C. According to the obtained results, the most selective catalysts present a low Nb-incorporation on the NiO lattice with a large amount of tiny Nb2O5 nanoparticles covering NiO crystallites. This work presents, for the first time, a complete electrochemical characterization of Nb-doped NiO catalysts showing a correlation between electrochemical properties and catalytic performance.