Shixiang Lu

Photocatalytic degradation in aqueous solution using quantum-sized ZnO particles supported on sepiolite.

Quantum-sized ZnO particles supported on sepiolite (ZnO/sepiolite) was prepared by sol-gel method using the sepiolite of acid activation as carrier, zinc acetate dihydrate (Zn(CH(3)COO)(2).2H(2)O) and lithium hydroxide monohydrate (LiOH.H(2)O) as raw material. The size of ZnO which supported on fibrous sepiolite is about 5 nm when calcined at 200 degrees C. The behavior of ZnO/sepiolite composites in the degradation of C.I. Reactive Blue 4 was investigated. Under the optimal preparation conditions, when the content of ZnO was about 70 wt.% in the nanocomposites, the photocatalytic property of the ZnO/sepiolite was excellent. The degradation rate of 20 mg/L C.I. Reactive Blue 4 could get to 98% in 120 min at room temperature when the concentration of catalyst was 0.2 g/L. The photocatalytic decomposition of organic pollutants accords with a pseudo first-order kinetic. The pH and H(2)O(2) influence the degradation rate of the ZnO/sepiolite. The experiment indicated that after the catalyst had been used 5 times repeatedly, the degradation rate had been still above 80%.

Fabrication of superhydrophobic Au–Zn alloy surface on a zinc substrate for roll-down, self-cleaning and anti-corrosion properties

Superhydrophobic Au–Zn alloy surfaces have been fabricated successfully on a zinc substrate via chemical substitution deposition and subsequent annealing treatment. The resulting surfaces exhibited remarkable superhydrophobicity with a WCA of 170 ± 2° and a WSA smaller than 1° without any organic modification. The surface morphologies and chemical compositions were investigated using field emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDS), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), and the surface roughness was analyzed by atomic force microscopy (AFM). The theoretical mechanism for superhydrophobicity and wettability were also analyzed. The surface wettability changed from superhydrophilicity to superhydrophobicity with a stable Cassie–Baxter state via thermal treatment, which caused the generation of Au–Zn alloys (including AuZn3 and AuZn) and ZnO, and the formation of micro-/nano-binary architectures. The resulting superhydrophobic Au–Zn alloy surfaces exhibited exquisite roll-down, self-cleaning, and excellent anti-corrosion properties, and also had a firm mechanical property about 10 N, and this might have important values for more potential applications. The corrosion current density was reduced by more than 2 orders of magnitude for the resulting superhydrophobic surface in comparison with the untreated zinc surface and this should be ascribed to the contribution of Au–Zn alloys on the surface.

Controllable wettability of micro- and nano-dendritic structures formed on aluminum substrates

A superhydrophilic surface with a static water contact angle of 4° ± 2° via two-step immersion process and a superhydrophobic surface with a static water contact angle of 169° ± 2° and a sliding angle of almost 0° via successive thermal treatment have been successfully fabricated on aluminum substrates. Surface morphologies and chemical compositions were investigated using field emission scanning electron microscopy, X-ray powder diffraction and X-ray photoelectron spectroscopy, and the formation mechanism was also analyzed. The thermal treatment, which causes the generation of oxides and the appearance of nano-sized particles, is very important for the surface characteristic transformation from superhydrophilicity to superhydrophobicity. The effects of various experimental parameters on wettability, corrosion resistance, anti-icing and deicing properties, stability and large-area preparation were also studied. The corrosion rate of the as-prepared superhydrophobic surface decreases by about 57.6 times compared with that of the untreated aluminum surface and about 34.8 times compared with that of the pure copper surface. These excellent properties of the superhydrophobic surface may be favorable for its potential applications and industrialization.

Controlled growth of CuO–Cu3Pt/Cu micro-nano binary architectures on copper substrate and its superhydrophobic behavior

A facile, simple and novel method for controllable fabrication of a superhydrophobic surface was developed by spontaneous deposition and subsequent annealing on a copper substrate. The surface morphologies, chemical compositions and hydrophobicity of the as-prepared surfaces were investigated using field emission scanning electron microscopy, X-ray diffractometry, X-ray photoelectron spectroscopy and contact angle measurements. The superhydrophobic surface was composed of a hierarchical structure of CuO–Cu3Pt/Cu. At the optimal conditions, the surface showed good superhydrophobicity with a water contact angle of about 170 ± 2° and a sliding angle of approximately 0 ± 2°. Additionally, the formation mechanism of the superhydrophobic surface was studied. The as-prepared superhydrophobic surface exhibited good nonsticking behavior, long-term stability, and a large buoyancy force, which offers possibilities for potential applications.

First-principles study of electronic structures and photocatalytic activity of low-Miller-index surfaces of ZnO

First-principles calculations have been performed to investigate the electronic structures and optical properties of the main low-Miller-index surfaces of ZnO: nonpolar (101¯0) and (112¯0) surfaces as well as polar (0001)-Zn and (0001¯)-O surfaces. According to the structure optimization results, there are similar relaxation behaviors for the (101¯0) and (112¯0) surfaces, both with a strong tilting of the surface Zn-O dimers and an obvious contraction of the surface bonds. For the polar surfaces, the surface double layers both tend to relax inwards, but the largest relaxation is found on the (0001¯)-O surfaces. The calculated band gaps are 0.56, 0.89, 0.21, and 0.71 eV for (101¯0), (112¯0), (0001)-Zn and (0001¯)-O surfaces, respectively. For the nonpolar (101¯0) and 112¯0 surfaces, the Fermi levels locate at the valence band maximum, which are similar to that of bulk ZnO. The surface states in the conduction band lead to the increased Fermi level and cause the n-type conduction behavior for (0001)-Zn surf...

Fabrication of Au–AlAu4–Al2O3 superhydrophobic surface and its corrosion resistance

Superhydrophobic Au–AlAu4–Al2O3 surfaces have been successfully fabricated on aluminum substrate via immersion in chloroauric acid (HAuCl4) aqueous solution and subsequent annealing treatment. The morphologies of the surfaces exhibit dendritic structures. The surface with remarkable superhydrophobic properties has a water contact angle of 171 ± 2° and a sliding angle of approximately 0°. The effects of the immersion time, immersion concentration, annealing time and annealing temperature on surface wettability were investigated in detail. The corrosion resistance of the untreated aluminum surface and the resulting Au–AlAu4–Al2O3 surface were also investigated via the Tafel extrapolation method. The corrosion current densities are reduced by more than 1 order of magnitude for the resulting surface in comparison with the untreated aluminum surface. The anticorrosion properties of the surfaces get better over the immersion time and this may be due to the generation of corrosion products, which can prevent the corrosion process and protect the substrates. Moreover, the low current density of the resulting superhydrophobic surface demonstrates its excellent corrosion resistance.

Controllable fabrication of stable superhydrophobic surfaces on iron substrates

Stable superhydrophobic structures were successfully prepared on iron substrates by etching in hydrochloric acid followed by zinc coating. The zinc film was electrochemically deposited on the etched iron substrate and then annealed at 180 °C. The morphology and chemical composition of the prepared surfaces were investigated by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic force microscope (AFM), energy-dispersive X-ray (EDX) analysis and X-ray photoelectron spectroscopy (XPS). The wetting properties of the surfaces upon each processing step were evaluated using water contact angle (WCA) measurements. At the optimal condition, the surface displayed a superhydrophobic character with a WCA of about 163 ± 2° and a low sliding angle of about 0 ± 2°. The experimental conditions, such as electrolyte concentration, electroplating time, annealing condition, and etching time were investigated to determine their effects on the superhydrophobicity. It was also demonstrated that the as-prepared superhydrophobic surfaces exhibited anti-corrosion properties and a long-term stability. The freezing properties of the superhydrophobic surfaces were also investigated.

Synthesis of tin superhydrophobic surfaces on zinc substrates

A superhydrophobic surface with a water contact angle of 159 ± 2° and a sliding angle of 2 ± 2° on a zinc substrate is reported in this article. The process is composed of etching, replacement deposition and annealing treatment. The surface morphologies, chemical compositions and hydrophobicity of the as-prepared surfaces were investigated using a scanning electron microscope, powder X-ray diffraction analysis, X-ray photoelectron spectroscopy and contact angle measurements. The superhydrophobicity of the fabricated surface results from composite structures which consist of densely packed nanoscale particles composed of tin on microscale cavities. The optimal conditions and the formation mechanism of the superhydrophobic surfaces were also studied. Moreover, the potentiodynamic polarization shows that the as-prepared superhydrophobic surface has excellent corrosion resistance, indicating promising industrial applications.

Fabrication of stable homogeneous superhydrophobic HDPE/graphene oxide surfaces on zinc substrates

Homogeneous superhydrophobic coatings were prepared on zinc substrates using ethanol–xylene solutions of high-density polyethylene (HDPE) containing 0, 1 or 5 wt% graphene oxide (GO) at room temperature. The resulting films display a superhydrophobic character with a static water contact angle higher than 150°. The superhydrophobic films provide an effective corrosion-resistant coating for the zinc interface upon immersion in an aqueous solution of sodium chloride (3% NaCl) for up to 29 days. The corrosion process was investigated by following the change of the water contact angle over time and by electrochemical means. The presence of GO in the HDPE film was found to increase the corrosion resistance.

Robust dendritic Ag–Fe2O3/Fe surfaces with exquisite catalytic properties

In this work, a facile approach was developed for producing stable Ag–Fe2O3/Fe superhydrophobic surfaces (SHSs) with dendritic structures. The hierarchical structures were fabricated on iron substrates through etching in a hydrochloric acid aqueous solution and a simple replacement deposition process was carried out without any organic modification, followed by annealing. The contact angle can reach 164 ± 1° and the sliding angle is almost 2 ± 1°. By comparison, the catalytic properties of the hydrophilic sample and SHS were examined. The SHS exhibited excellent catalytic performance. The rate constant of SHS was 3.00 × 10−3 s−1, which was about three times higher than that of the hydrophilic sample without annealing, and the degradation rate was maintained above 90% after ten recycles. The experimental results showed that the as-prepared SHSs exhibited excellent catalytic, self-cleaning, anti-corrosion, and anti-icing properties.