Enhanced Photoelectrochemical Properties from Mo-Doped TiO2 Nanotube Arrays Film

Titanium dioxide-supported mercury photocatalysts for oxidative removal of hydrogen sulfide from the air using a portable air purification unit

Photocatalytic removal of gaseous hydrogen sulfide (H2S) has been studied through the control of key process variables using a prototype air purifier (AP) fabricated with titanium dioxide (TiO2)-supported mercury. The performance of Hg/TiO2 systems, prepared with different Hg mass proportions over TiO2 (such as 0.1%, 1%, 2%, and 5%), is measured against 5 ppm H2S at 160 L min-1 under UV irradiation. Accordingly, their removal efficiency (RE) values after 360 s are 40.3%, 74.8%, 99.3%, and 99.9%, respectively (relative to 33.5% of AP (TiO2)). An AP with a 2% Hg/TiO2 unit achieves a clean air delivery rate of 32 L min-1 with kinetic reaction rate (r (at 10% RE)) of 0.774 mmol h-1 g-1, quantum yield of 2.19E-02 molecules photon-1, and space-time yield of 1.46E-04 molecules photon-1 mg-1. The superior photocatalytic performance of Hg/TiO2 is supported by superoxide anion and hydroxyl radicals formed in dry air and humid nitrogen (N2) environments, respectively. A density functional theory simulation suggests that the presence of oxygen vacancies should promote the disparities in the electronic structure to subsequently affect the reaction pathways and energetics. The presence of moisture enhances the robust formation of a mercury-OH bond to favorably yield β-mercury sulfide from H2S.

A mesoporous Mo and N Co-doped TiO2 nanocomposite with enhanced photocatalytic efficiency

This study reports the synthesis of a mesoporous Mo and N codoped anatase TiO2 nanocomposite with many oxygen vacancies using a simple one-step hydrothermal method and subsequent calcination treatment. Both Mo and N were effectively co-incorporated into the anatase phase of TiO2 without MoOx phase segregation. The codoped catalyst demonstrated a mesoporous architecture with a surface area of 107.48 m2 g-1 and a pore volume of 0.2974 cm3 g-1. X-ray photoelectron spectroscopy confirmed that both Mo and N dissolved in the TiO2 lattice and created induced oxygen vacancies. The interaction of the dopants (Mo and N) and oxygen vacancies clearly affected TiO2 crystal formation. Photocatalytic performance of the nanocomposite was investigated in terms of the decomposition of methyl orange at a concentration of 50 mg L-1 in an aqueous solution. The results revealed a significant methyl orange degradation of up to 99.6% after 30 min irradiation under a UV light. The impressive performance of the nanocomposite is assigned to the synergetic effect of important factors, including the co-doping of metallic (Mo) and non-metallic (N) elements, oxygen vacancy defects, bandgap, crystallite size, mesoporous structure, and BET surface area.

Interfacial and Electronic Modulation of M-Bridged Heterostructures with L-Tryptophan and Transition Metallic Oxides: Enhancing Corrosion Resistance and Photocatalytic Activity

Despite remarkable advancements in multilayer composite materials, achieving controlled growth on stationary platforms for optimal corrosion protection and photocatalytic capabilities remains a challenge. In this study, we introduce an innovative approach by integrating bifunctional metal-organic frameworks (MOFs) into plasma-electrolyzed layers made on AZ31 Mg alloy. Metallic oxides of Zr, Ti, and W serve as new pivotal centers for MOF formation, while L-tryptophan (Trp) acts as an organic linker. This innovative approach establishes an efficient electron transport system that acts as a functional pathway for creating highly effective and versatile materials. The tunable structure of the MOF/plasma electrolyzed layer enables it to concurrently display electrochemical stability and photocatalytic activity for the photodegradation of organic pollutants. Remarkably, the WOF complex emerges as a standout performer, effectively shielding the substrate from corrosive anion attacks. This sample showcases exceptional photocatalytic efficiency of 99.61% for crystal violet solution, with sustained performance after five cycles and a 72 h corrosion test (96.55% and 98.39% degradation, respectively). Moreover, DFT calculations elucidate the fundamental bonding modes between MOFs and inorganic constituents, delivering comprehensive insights into their structural formation. Our research addresses the critical challenge of achieving controlled growth for enhanced corrosion resistance and photocatalytic activity, demonstrating a novel pathway for creating multifunctional materials with practical applications across various fields.

Visible-light-driven peroxymonosulfate activation by robust TiO2-base nanoparticles for efficient removal of sulfamethoxazole

In this study, a novel bimetallic Co-Mo-TiO2 nanomaterial was fabricated through a simple two-step method, and applied as photocatalyst to activate peroxymonosulfate (PMS) with high efficiency for sulfamethoxazole (SMX) removal under visible light. Nearly 100% of SMX was degraded within 30 min in Vis/Co-Mo-TiO2/PMS system, and its kinetic reaction rate constant (0.099 min-1) was 24.8 times higher compare with the Vis/TiO2/PMS system (0.014 min-1). Moreover, the quenching experiments and the electronic spin resonance analysis results confirmed that both 1O2 and SO4•- were the dominant active species in the optimal system, and the redox cycles of Co3+/Co2+ and Mo6+/Mo4+ promoted the generation of the radicals during the PMS activation process. Additionally, the Vis/Co-Mo-TiO2/PMS system exhibited a wide working pH range, superior catalytic performance toward different pollutants and excellent stability with 92.8% SMX removal capacity retention after three consecutive cycles. The result of density functional theory (DFT) suggested that Co-Mo-TiO2 exhibited a high affinity for PMS adsorption, as indicated by the length O-O bond from PMS and the Eads of the catalysts. Finally, the possible degradation pathway of SMX in optimal system was proposed through intermediate identification and DFT calculation, and a toxicity assessment of the by-products was also conducted.

Reconfiguring the Electronic Structure of Heteroatom Doped Carbon Supported Bimetallic Oxide@Metal Sulfide Core-Shell Heterostructure via In Situ Nb Incorporation toward Extrinsic Pseudocapacitor

High-energy-density battery-type materials have sparked considerable interest as supercapacitors electrode; however, their sluggish charge kinetics limits utilization of redox-active sites, resulting in poor electrochemical performance. Here, the unique core-shell architecture of metal organic framework derived N-S codoped carbon@Co_x S_y micropetals decorated with Nb-incorporated cobalt molybdate nanosheets (Nb-CMO₄ @C_x S_y NC) is demonstrated. Coordination bonding across interfaces and π-π stacking interactions between CMO₄ @C_x S_y and N and, S-C can prevent volume expansion during cycling. Density functional theory analysis reveals that the excellent interlayer and the interparticle conductivity imparted by Nb doping in heteroatoms synergistically alter the electronic states and offer more accessible species, leading to increased electrical conductivity with lower band gaps. Consequently, the optimized electrode has a high specific capacity of 276.3 mAh g^-1 at 1 A g^-1 and retains 98.7% of its capacity after 10 000 charge-discharge cycles. A flexible quasi-solid-state SC with a layer-by-layer deposited reduced graphene oxide /Ti₃ C₂ T_X anode achieves a specific energy of 75.5 Wh kg^-1 (volumetric energy of 1.58 mWh cm^-3 ) at a specific power of 1.875 kWh kg^-1 with 96.2% capacity retention over 10 000 charge-discharge cycles.

Fabrication of Ni/TiO2 visible light responsive photocatalyst for decomposition of oxytetracycline

Nickel-impregnated TiO₂ photocatalyst (NiTP) responding to visible light was prepared by the liquid phase plasma (LPP) method, and its photoactivity was evaluated in degrading an antibiotic (oxytetracycline, OTC). For preparing the photocatalyst, nickel was uniformly impregnated onto TiO₂ (P-25) powder, and the nickel content increased as the number of LPP reactions increased. In addition, the morphology and lattice of NiTP were observed through various instrumental analyses, and it was confirmed that NiO-type nanoparticles were impregnated in NiTP. Fundamentally, as the amount of impregnated nickel in the TiO₂ powder increased sufficiently, the band gap energy of TiO₂ decreased, and eventually, the NiTP excited by visible light was synthesized. Further, OTC had a decomposition reaction pathway in which active radicals generated in OTC photocatalytic reaction under NiTP were finally mineralized through reactions such as decarboxamidation, hydration, deamination, demethylation, and dehydroxylation. In effect, we succeeded in synthesizing a photocatalyst useable under visible light by performing only the LPP single process and developed a new advanced oxidation process (AOP) that can remove toxic antibiotics.

Electrochemical Oxidation of Ti15Mo Alloy-The Impact of Anodization Parameters on Surface Morphology of Nanostructured Oxide Layers

It is well-known that the structure and composition of the material plays an important role in the processes occurring at the surface. In this paper, a surface morphology of nanostructured oxide layers electrochemically grown on Ti15Mo, tuned by applying different anodization parameters, was investigated in detail. The one-step anodization of Ti15Mo alloy was performed at room temperature in an ethylene glycol-based electrolyte containing 0.11 M NH4F and 1.11 M H2O. Different anodization times (ranging from 5 to 60 min) and applied potentials (40-100 V) were tested, and the surface morphology, elemental content, and crystalline structure were monitored by scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), and X-ray diffractometry (XRD), respectively. The results showed that contrary to the multistep anodization of titanium foil, the surface morphology of anodic oxide obtained via the one-step process contains the nanoporous outer layer covering the nanotubular structure. What is more, the pore diameter (Dp) and interpore distance (Dint) of such layers exhibit different trends than those observed for anodization of pure titanium. In particular, at a certain potential range, a decrease in both Dp and Dint with increasing potential was observed. However, independently on the used anodization conditions, the elemental content of oxide layers remained similar, showing the amount of molybdenum at c.a. 15 wt.%. Finally, the amorphous nature of as-anodized layers was confirmed, and their optical band-gap was determined from the diffuse reflectance UV-Vis spectra. It was found that Eg is tunable to some extent by changing the anodizing potential. However, further thermal treatment in air at 400 °C resulted in the anatase phase formation that was accompanied by a significant Eg reduction. Therefore, we believe that the presented results will greatly contribute to the understanding of anodic formation of nanostructured functional oxide layers with tunable properties that can be applied in various fields.