Development of PSA@PS-TiO2 nanocomposite photocatalyst: structure, mechanism, and application using response surface designs and molecular modeling.

Using periwinkle shell ash (PSA) and polystyrene (PS), a new-fangled PSA@PS-TiO2 photocatalyst was fabricated. The morphological images of all the samples studied using a high-resolution transmission electron microscope (HR-TEM) showed a size distribution of 50-200 nm for all samples. The SEM-EDX showed that the membrane substrate of PS was well dispersed, confirming the presence of anatase/rutile phases of TiO2, and Ti and O2 were the major composites. Given the very rough surface morphology (atomic force microscopy (AFM)) due to PSA, the main crystal phases (XRD) of TiO2 (rutile and anatase), low bandgap (UVDRS), and beneficial functional groups (FTIR-ATR), the 2.5 wt.% of PSA@PS-TiO2 exhibited better photocatalytic efficiency for methyl orange degradation. The photocatalyst, pH, and initial concentration were investigated and the PSA@PS-TiO2 was reused for five cycles with the same efficiency. Regression modeling predicted 98% efficiency and computational modeling showed a nucleophilic initial attack initiated by a nitro group. Therefore, PSA@PS-TiO2 nanocomposite is an industrially promising photocatalyst for treating azo dyes, particularly, methyl orange from an aqueous solution.

Molecular Bonding of Predissociative CO on Fe(100): Molecular Orbital Perspective.

On Fe(100), CO molecules can get activated efficiently so that CO bond breaking occurs with its transition state in close connection to the adsorbate. The CO bonding thus serves as a prototype model, nicely representing a balance of two simultaneous processes, namely, bond making with the surface and bond breaking within the adsorbate. Such unique configuration highlighting the interplay of two fundamental processes in one adsorption geometry, about which chemists have often fantasized, provides a viable solution to understand the very fundamental aspects of chemistry exemplified in a broad range of disciplines. Using density functional theory calculations, in this paper, we get a glimpse into how the CO bond activation is gestated and initiated in the adsorbate, wherein orbital cooperation in CO activation is evidenced by external CO bond making with the metal and internal CO bond breaking. We find that the symmetry breaking of occupied molecular orbitals in both 5σ and 1π symmetries marks efficient CO bond activation, which is reinforced by 1π → 2π excitations and 2π backdonation that are coupled with the symmetry transition of partially occupied 2π orbitals to a rotational symmetry. Our findings promote our knowledge of CO bond activation beyond the established picture of 5σ donation and 2π backdonation without symmetry breaking and may have insightful implications on orbital control of molecular activation, with further possible impact on elucidating the physical basis of heterogeneous catalysis.

CoPi/Co(OH)2 Modified Ta3N5 as New Photocatalyst for Photoelectrochemical Cathodic Protection of 304 Stainless Steel.

In this work, CoPi and Co(OH)2 nanoparticles were deposited on the surface of Ta3N5 nanorod-arrays to yield a novel broad-spectrum response photocatalytic material for 304 stainless steel photocatalytic cathodic protection. The Ta3N5 nanorod-arrays were prepared by vapor-phase hydrothermal (VPH) and nitriding processes and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV-Vis spectroscopy, respectively, to obtain morphologies, crystal structures, surface compositions, and light response range. In order to analyze the performance improvement mechanism of CoPi/Co(OH)2 on Ta3N5 nanorod-arrays, the electrochemical behavior of modified and unmodified Ta3N5 was obtained by measuring the open circuit potential and photocurrent in 3.5 wt% NaCl solution. The results revealed that the modified Ta3N5 material better protects 304 stainless steel at protection potentials reaching -0.45 V.

Influence of Temperature on Corrosion Behavior of 2A02 Al Alloy in Marine Atmospheric Environments.

The corrosion behavior of 2A02 Al alloy under 4 mg/cm² NaCl deposition at different temperatures (from 30 to 80 °C) has been studied. This corrosion behavior was researched using mass-gain, scanning electron microscopy-SEM, laser scanning confocal microscopy-LSCM, X-ray photoelectron spectroscopy-XPS and other techniques. The results showed and revealed that the corrosion was maximal at 60 °C after 200 h of exposure. The increase of temperature not only affected the solubility of oxygen gas in the thin film, but also promoted the transport of ions (such as Cl-), and the formation of protective AlO(OH), which further affects the corrosion speed.

Nanostructured superhydrophobic polysiloxane coating for high barrier and anticorrosion applications in marine environment.

The use of epoxy and polyurethane coatings as marine topcoats, have been influenced by their inherent high surface energy property which increases their affinity to water and microorganisms. Thus, their susceptibility to degradation is enhanced. Because of this defect, recently, nanostructured hydrophobic and superhydrophobic polysiloxane coatings are being preferred as topcoats. But the appropriate nanoparticle size and matrix:filler ratio which provide guide for the design of desired topcoats are scarcely available. In view of this, a series of hydrophobic and superhydrophobic coatings were prepared by sol-gel process based on perfluorodecyltrichlorosilane (FDTS), different nanoZnO particles and poly(dimethylsiloxane) (PDMS):nanoZnO ratios. The liquid repellency, surface morphology and roughness of the coatings were conducted by use of contact angle goniometer, field emission scanning electron microscopy and atomic force microscopy, respectively. Additionally, the electrochemical and salt spray corrosion tests were conducted. According to the results, modifications of the coatings showed that anticorrosion performance was considerably influenced by the surface properties which were dependent on nanoZnO size and PDMS:nanoZnO ratio. Remarkably, the optimum effect was observed on the superhydrophobic coating based on 30 nm ZnO and 1:1 ratio. This displayed highest anticorrosion performance, and is therefore recommended as a guide for the design of marine topcoats.

Fabrication of FDTS-modified PDMS-ZnO nanocomposite hydrophobic coating with anti-fouling capability for corrosion protection of Q235 steel.

Perfluorodecyltrichlorosilane-based poly(dimethylsiloxane)-ZnO (FDTS-based PDMS-ZnO) nanocomposite coating with anti-corrosion and anti-fouling capabilities has been prepared using a one-step fabrication technique. XPS analysis and contact angle measurements showed the fluorine content to increase, while the hydrophobicity of the coatings decreased with addition of FDTS. XRD analysis revealed existence of ZnO nanoparticles of dimensions ranging from 11.45 to 93.01nm on the surface of coatings, with the mean particle size decreasing with FDTS addition, and was confirmed by SEM and TEM observations. Interestingly, the anti-corrosion performance and mechanical properties of the coatings increased remarkably on addition of FDTS. Indeed, the observed low adhesion strength, surface energies and the outstanding anti-corrosive properties imply that the obtained coating would be useful in anti-fouling applications.

Electrochemical transformation of thichloroethylene in groundwater by Ni-containing cathodes.

In this study, we evaluate the use of different stainless steel (SS) materials as cost-effective cathode materials for electrochemical transformation of trichloroethylene (TCE) in contaminated groundwater. Ni, which is present in certain SS, has low hydrogen overpotential that promotes fast formation of atomic hydrogen and, therefore, its content can enhance hydrodechlorination (HDC). We a flow-through electrochemical reactor with a SS cathode followed by an anode. The performance of Ni containing foam cathodes (Fe/Ni and Ni foam) was also evaluated for electrochemical transformation of TCE in groundwater. SS type 316 (12% Ni) removed 61.7% of TCE compared to 52.6% removed by SS 304 (9.25% Ni) and 37.5% removed by SS 430 (0.75% Ni). Ni foam cathode produced the highest TCE removal rate (68.4%) compared with other cathodes. The slightly lower performance of SS type 316 mesh is balanced by the reduction in treatment costs for larger-scale systems. The results prove that Ni content in SS highly influences TCE removal rate.

Theoretical and experimental studies on the corrosion inhibition potentials of some purines for aluminum in 0.1 M HCl.

Experimental aspect of the corrosion inhibition potential of adenine (AD), guanine (GU) and, hypoxanthine (HYP) was carried out using weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods while the theoretical aspect of the work was carried out by calculations of semi-empirical parameters (for AM1, MNDO, CNDO, PM3 and RM1 Hamiltonians), Fukui functions and inhibitor-metal interaction energies. Results obtained from the experimental studies were in good agreement and indicated that adenine (AD), guanine (GU) and hypoxanthine (HYP) are good adsorption inhibitors for the corrosion of aluminum in solutions of HCl. Data obtained from electrochemical experiment revealed that the studied purines functioned by adsorption on the aluminum/HCl interface and inhibited the cathodic half reaction to a greater extent and anodic half reaction to a lesser extent. The adsorption of the purines on the metal surface was found to be exothermic and spontaneous. Deviation of the adsorption characteristics of the studied purines from the Langmuir adsorption model was compensated by the fitness of Flory Huggins and El Awardy et al. adsorption models. Quantum chemical studies revealed that the experimental inhibition efficiencies of the studied purines are functions of some quantum chemical parameters including total energy of the molecules (TE), energy gap (E L-H), electronic energy of the molecule (EE), dipole moment and core-core repulsion energy (CCR). Fukui functions analysis through DFT and MP2 theories indicated slight complications and unphysical results. However, results obtained from calculated Huckel charges, molecular orbital and interaction energies, the adsorption of the inhibitors proceeded through the imine nitrogen (N5) in GU, emanine nitrogen (N7) in AD and the pyridine nitrogen (N5) in HPY.