Preparation of Gd-Doped TiO2 Nanotube Arrays by Anodization Method and Its Photocatalytic Activity for Methyl Orange Degradation

In situ evolution of bulk-active γ-CoOOH with immobilized Gd dopants enabling efficient oxygen evolution electrocatalysis

Promoting the in situ reconstruction of transition metal (TM)-based precatalysts into low-crystalline and well-modified TM (oxy)hydroxides (TMOxHy) during the alkaline oxygen evolution reaction (OER) is crucial for enhancing their catalytic performances. In this study, we incorporated gadolinium (Gd) into a cobalt hydroxide precatalyst, achieving a deep reconstruction into cobalt oxyhydroxide (γ-CoOOH) while retaining the incorporated Gd during the activation process of the alkaline OER. The unconventional non-leaching Gd dopants endow γ-CoOOH with reduced crystallinity, increasing the exposure of electrolyte-accessible Co atoms and enhancing its bulk activity. Furthermore, the modulation of the electronic structure of γ-CoOOH substantially boosts the intrinsic activity of the active Co sites. As a result, when supported on nickel foam, the catalyst exhibits remarkable alkaline OER performance, achieving a current density of 100 mA cm-2 at a low overpotential of approximately 327 mV. Notably, an ultrahigh current density of 1000 mA cm-2 is robustly maintained for 5 days, highlighting its immense potential for practical applications in large-scale hydrogen production.

Advancements in TiO2-based photocatalysis for environmental remediation: Strategies for enhancing visible-light-driven activity

Researchers have focused on efficient techniques for degrading hazardous organic pollutants due to their negative impacts on ecological systems, necessitating immediate remediation. Specifically, TiO2-based photocatalysts, a wide-bandgap semiconductor material, have been extensively studied for their application in environmental remediation. However, the extensive band gap energy and speedy reattachment of electron (e-) and hole (h+) pairs in bare TiO2 are considered major disadvantages for photocatalysis. This review extensively focuses on the combination of semiconducting photocatalysts for commercial outcomes to develop efficient heterojunctions with high photocatalytic activity by minimizing the e-/h+ recombination rate. The improved activity of these heterojunctions is due to their greater surface area, rich active sites, narrow band gap, and high light-harvesting tendency. In this context, strategies for increasing visible light activity, including doping with metals and non-metals, surface modifications, morphology control, composite formation, heterojunction formation, bandgap engineering, surface plasmon resonance, and optimizing reaction conditions are discussed. Furthermore, this review critically assesses the latest developments in TiO2 photocatalysts for the efficient decomposition of various organic contaminants from wastewater, such as pharmaceutical waste, dyes, pesticides, aromatic hydrocarbons, and halo compounds. This review implies that doping is an effective, economical, and simple process for TiO2 nanostructures and that a heterogeneous photocatalytic mechanism is an eco-friendly substitute for the removal of various pollutants. This review provides valuable insights for researchers involved in the development of efficient photocatalysts for environmental remediation.

Synthesis, characterization, mechanical and magnetic characteristics of Gd3+ /PO4 3 - substituted zircon for application in hard tissue replacements

The study reports on the use of sol-gel technique to yield zircon type [Zr(1-0.1-x) GdxTi0.1 ] [(SiO4 )1-x (PO4 )x ] solid solution. Titanium has been used as a mineralizer to trigger zircon formation while equimolar concentrations of Gd3+ and PO4 3- were added to determine their accommodation limits in the zircon structure. The crystallization of t-ZrO2 as a dominant phase alongside the crystallization of m-ZrO2 and zircon were detected at 1200°C while their further annealing revealed the formation of zircon as a major phase at 1300°C. Heat treatment at 1400°C revealed the formation of zircon-type solid solution [Zr(1-0.1-x) Gdx Ti0.1 ][(SiO4 )1-x (PO4 )x ] comprising the accommodation of 10 mol.% of Gd3+ /PO4 3- at the zircon lattice. Beyond 10 mol.% of Gd3+ /PO4 3- , the crystallization of GdPO4 as a secondary phase is noticed. Structural analysis revealed the expansion of zircon lattice due to the simultaneous occupancy of Gd3+ /PO4 3- for the corresponding Zr4+ /SiO4 4- sites. The mechanical strength of single-phase zircon solid solution was higher in comparison to that of multiphase materials, namely in the presence of GdPO4 formed as a secondary phase in samples with added equimolar Gd3+ /PO4 3- contents beyond 10 mol.%. Nevertheless, the paramagnetic behavior of the samples demonstrated a steady surge as a function of enhanced Gd3+ content.

Effective Reinforcement of Visible Light Photocatalytic and Gas Sensing Characteristics of Nanocrystalline TiO2: Gd-Based Nb and Mo Dopants

Efficient compositions for the selective detection of ethanol gas and the removal of organic contaminants were realized by codoping of (Gd, Nb) and (Gd, Mo) ions into TiO2. TiO2, Ti0.96Gd0.01Nb0.03O2, and Ti0.96Gd0.01Mo0.03O2 samples were prepared by a coprecipitation method. For all compositions, a crystalline anatase phase of TiO2 was detected. Compared to pure TiO2, the absorption edges of Ti0.96Gd0.01Nb0.03O2 and Ti0.96Gd0.01Mo0.03O2 samples were red-shifted, further broadening towards visible light. The morphological studies demonstrate that the grains of TiO2 were more refined after (Gd, Nb) and (Gd, Mo) codoping. The photocatalytic efficiency of the Ti0.96Gd0.01Mo0.03O2 catalyst for degrading 20 mg/L reactive yellow 145, brilliant green, and amoxicillin was 98, 95, and 93% in 90 min, respectively. The reusability experiments indicate that the Ti0.96Gd0.01Mo0.03O2 catalyst had high stability during reuse. The high photocatalytic activity of the Ti0.96Gd0.01Mo0.03O2 catalyst was correlated to the broad visible-light absorption and effective separation of electron-hole pairs by Gd3+ and Mo6+ cations. The gas sensing characteristic is reflected by the high sensitivity of the Ti0.96Gd0.01Nb0.03O2 sensor to ethanol gas in the presence of different gases at 275 °C. The obtained results indicated that the (Gd, Mo) mixture could more effectively induce the photocatalytic properties of TiO2 while (Gd, Nb) dopants were the best for reinforcing its sensing characteristics.

Removal of organic dyes and free radical assay by encapsulating polyvinylpyrrolidone and Tinospora Cordifolia in dual (Co-Cu) doped TiO2 nanoparticles

Aquatic pollution refers to any water that has been used and discarded in different water bodies by industrial and commercial activities which contains a wide range of toxic substances and required treatment so that water can be safely reused for various purposes. In present paper, polymer polyvinylpyrrolidone (PVP) and plant Tinospora Cordifolia (T. Cordifolia) encapsulated dual doped cobalt-copper titanium dioxide nanoparticles (Co-Cu TNPs) has been synthesized via microwave-assisted method for the degradation aquatic pollutant dyes: Methyl Orange (MO) & Methylene Blue (MB). Using the encapsulated dual doped Co-Cu TNPs, free radical assays (2,2-diphenyl-1-picrylhydrazyl: DPPH; Hydrogen peroxide: HP & Nitric oxide: NO) were also performed. Several physicochemical properties of encapsulated TNPs were examined using a variety of characterization techniques that helps in photocatalytic and antioxidant activity. The encapsulated TNPs exhibit tetragonal crystal lattice having average particles size between 25 and 38 nm with spherical shape morphology. The bandgap of encapsulated dual doped Co-Cu TNPs was found in the range of 3.25-3.29 eV. The binding of encapsulated dual doped Co-Cu TNPs were also calculated by using XPS which confirms the presence of dopants. The photocatalytic activity was performed with using control experiment and using encapsulated dual doped Co-Cu TNPs against MO and MB dyes. The results revealed that the degradation was observed up to 100% for the both MO and MB dyes. Also, antioxidant activity of encapsulated dual doped Co-Cu TNPs was observed against the DPPH, HO and NO assays.

Fabrication and Photocatalytic Properties of Electrospun Fe-Doped TiO2 Nanofibers Using Polyvinyl Pyrrolidone Precursors

For the removal of pollutants, a modified TiO₂ photocatalyst is attracting attention. Fe-doped TiO₂ nanofibers were prepared through a combination of electrospinning and calcination. Morphological characterization of the sample was conducted using field-emission scanning electron and transmission electron microscopy. The crystal structure of each sample was analyzed using high-resolution transmission electron microscopy, selected area electron diffraction, and Fast Fourier Transform imaging. The average diameter of the Fe-doped TiO₂ nanofibers was measured to be 161.5 nm and that of the pure TiO₂ nanofibers was 181.5 nm. The crystal phase when heat treated at 350 °C was anatase for TiO₂ nanofibers and rutile for Fe-doped TiO₂ nanofibers. The crystal phase of the TiO₂ matrix was easily transitioned to rutile by Fe-doping. The photocatalytic performance of each sample was compared via the photodegradation of methylene blue and acid orange 7 under ultraviolet and visible light irradiation. In the Fe-doped TiO₂ nanofibers, photodegradation rates of 38.3% and 27.9% were measured under UV irradiation and visible light, respectively. Although other catalysts were not activated, the photodegradation rate in the Fe-doped TiO₂ nanofibers was 9.6% using acid orange 7 and visible light. For improved photocatalytic activity, it is necessary to study the concentration control of the Fe dopant.

Synthesis and Characterization of ZnO-TiO2/Carbon Fiber Composite with Enhanced Photocatalytic Properties

Herein, we prepared a novel photocatalytic ZnO-TiO2 loaded carbon nanofibers composites (ZnO-TiO2-CNFs) via electrospinning technique followed by a hydrothermal process. At first, the electrospun TiO2 NP-embedded carbon nanofibers (TiO2-CNFs) were achieved using electrospinning and a carbonization process. Next, the ZnO particles were grown into the TiO2-CNFs via hydrothermal treatment. The morphology, structure, and chemical compositions were studied using state-of-the-art techniques. The photocatalytic performance of the ZnO-TiO2-CNFs composite was studied using degrading methylene blue (MB) under UV-light irradiation for three successive cycles. It was noticed that the ZnO-TiO2-CNFs nanocomposite showed better MB removal properties than that of other formulations, which might be due to the synergistic effects of carbon nanofibers and utilized metal oxides (ZnO and TiO2). The adsorption characteristic of carbon fibers and matched band potentials of ZnO and TiO2 combinedly help to boost the overall photocatalytic performance of the ZnO-TiO2-CNFs composite. The obtained results from this study indicated that it can be an economical and environmentally friendly photocatalyst.

Multi-Leg TiO2 Nanotube Photoelectrodes Modified by Platinized Cyanographene with Enhanced Photoelectrochemical Performance

Highly ordered multi-leg TiO2 nanotubes (MLTNTs) functionalized with platinized cyanographene are proposed as a hybrid photoelectrode for enhanced photoelectrochemical water splitting. The platinized cyanographene and cyanographene/MLTNTs composite yielded photocurrent densities 1.66 and 1.25 times higher than those of the pristine MLTNTs nanotubes, respectively. Open circuit VOC decay (VOCD), electrochemical impedance spectroscopy (EIS), and intensity-modulated photocurrent spectroscopy (IMPS) analyses were performed to study the recombination rate, charge transfer characteristics, and transfer time of photogenerated electrons, respectively. According to the VOCD and IMPS results, the addition of (platinized) cynographene decreased the recombination rate and the transfer time of photogenerated electrons by one order of magnitude. Furthermore, EIS results showed that the (platinized) cyanographene MLTNTs composite has the lowest charge transfer resistance and therefore the highest photoelectrochemical performance.

N,Fe-Doped Carbon Dot Decorated Gear-Shaped WO3 for Highly Efficient UV-Vis-NIR-Driven Photocatalytic Performance

The development of efficient and non-toxic photocatalysts with a full spectrum response is a primary strategy in the area of photocatalytically mediated pollutant elimination. Herein, we report the preparation of novel nitrogen and iron co-doped carbon dots/gear-shaped WO3 (N,Fe-CDs/G-WO3) with significantly improved broad-spectrum utilization. Characterization results demonstrated that the gear-shaped G-WO3, decorated by N,Fe-CDs with excellent electron transfer/reservoir properties, possessed abundant oxygen vacancies, had large specific surface areas, had multiple light-reflections and had a narrow band gap. As a result, the N,Fe-CDs/G-WO3 composite exhibited excellent photocatalytic activity towards the degradation of water contaminants under full spectrum irradiation. For example, the photodegradative efficiencies of rhodamine B (RhB) reached 81.4%, 97.1%, and 75% in 2 h, under ultraviolet, visible, and near-infrared (UV, vis, and NIR) light irradiation, respectively. Moreover, the N,Fe-CDs/G-WO3 composite also exhibited an outstanding photocatalytic degradation efficiency for other dyes, pharmaceuticals, and personal care products (PPCPs) like methylene blue (MB), ciprofloxacin (CIP), tetracycline hydrochloride (TCH), and oxytetracycline (OTC) (91.1%, 70.5%, 54.5%, and 47.8% in 3 h, respectively). The radical trapping experiments indicated that h+ and ·OH were the main reactive oxidative species (ROS), and the conversion between Fe (III) and Fe (II) played a key role in the photocatalytic reactions. Such a N,Fe-CD decorated material with brilliant photocatalytic activity has tremendous potential for application in environmental remediation.