ngjie Li

A one-step, cost-effective green method to in situ fabricate Ni(OH)2 hexagonal platelets on Ni foam as binder-free supercapacitor electrode materials

Nickel hydroxide (Ni(OH)2) is considered to be a promising alternative to the expensive and toxic RuO2 electrode material for high-performance supercapacitors; however, the fabrication method and electrochemical performance of suitable Ni(OH)2 structures are unsatisfactory. In the present work, a facile, cost-effective green method is developed to in situ fabricate Ni(OH)2 hexagonal platelets on Ni foam as a binder-free supercapacitor electrode with high performance. The Ni(OH)2 hexagonal platelets are self-grown on three-dimensional (3D) Ni foam by a one-step hydrothermal treatment of Ni foam in a 15 wt% H2O2 aqueous solution without the use of nickel salts, acids, bases, or post-treatments. The as-prepared Ni(OH)2 hexagonal platelets-Ni foam (HNF) electrode can be used directly as a supercapacitor electrode material, thereby avoiding the need for binders and conducting agents. The Ni(OH)2 hexagonal platelets demonstrate high capacitance (2534 F g−1 at a scan rate of 1 mV s−1) and excellent cycling stability (97% capacitance retention after 2000 cycles at a scan rate of 50 mV s−1). The fabrication method developed here has the significant advantage of low-cost, facile, green, and additive-free processing, and it is therefore a promising route for preparing self-supported metal (hydr)oxide electrodes for high-performance supercapacitors and other energy-storage devices.

Robust Biomimetic-Structural Superhydrophobic Surface on Aluminum Alloy

The following facile approach has been developed to prepare a biomimetic-structural superhydrophobic surface with high stabilities and strong resistances on 2024 Al alloy that are robust to harsh environments. First, a simple hydrothermal treatment in a La(NO3)3 aqueous solution was used to fabricate ginkgo-leaf like nanostructures, resulting in a superhydrophilic surface on 2024 Al. Then a low-surface-energy compound, dodecafluoroheptyl-propyl-trimethoxylsilane (Actyflon-G502), was used to modify the superhydrophilic 2024 Al, changing the surface character from superhydrophilicity to superhydrophobicity. The water contact angle (WCA) of such a superhydrophobic surface reaches up to 160°, demonstrating excellent superhydrophobicity. Moreover, the as-prepared superhydrophobic surface shows high stabilities in air-storage, chemical and thermal environments, and has strong resistances to UV irradiation, corrosion, and abrasion. The WCAs of such a surface almost remain unchanged (160°) after storage in air for 80 days, exposure in 250 °C atmosphere for 24 h, and being exposed under UV irradiation for 24 h, are more than 144° whether in acidic or alkali medium, and are more than 150° after 48 h corrosion and after abrasion under 0.98 kPa for 1000 mm length. The remarkable durability of the as-prepared superhydrophobic surface can be attributed to its stable structure and composition, which are due to the existence of lanthanum (hydr)oxides in surface layer. The robustness of the as-prepared superhydrophobic surface to harsh environments will open their much wider applications. The fabricating approach for such robust superhydrophobic surface can be easily extended to other metals and alloys.

Intelligent sponge with reversibly tunable super-wettability: robust for effective oil–water separation as both the absorber and filter tolerate fouling and harsh environments

We fabricate an intelligent and robust sponge by a one-step and low-cost ultrasonic-assisted dip coating (UADC) method, which involves the modification of the commercial sponge with TiO2 nanoparticles and a low-surface-energy compound (octadecanoic acid). The as-prepared sponge shows intelligent reversibly tunable super-wettability and exhibits robustness for effective oil–water separation. It can act as both the absorber and filter for the highly efficient separation of oil–water mixtures under different super-wettability conditions. More importantly, it has remarkably high chemical stability, which can separate oil–water mixtures in the extremely high acidic and alkaline environments as well as the extremely high salt concentration of seawater (such as 10 M H2SO4 and NaOH, and saturated NaCl media). Meanwhile, the as-prepared sponge has excellent antifouling ability, which shows self-cleaning performance during multiple fouling cycles. These extraordinary properties suggest that the as-prepared sponge will be a promising candidate for large-scale oil–water separation.

Morphology-Controllable Synthesis of CeO2on a Pt Electrode

Nanoscale cerium dioxides with shape of nanoparticles, nanorods, and nanotubes were electrochemically synthesized. The morphology of CeO2was modulated by changing electrode potential and potential direction. CeO2nanorods and CeO2nanotubes were synthesized via the potentiostatic and cyclic voltammeteric methods, respectively. The morphology and structure of the obtained CeO2were characterized by field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD). A possible formation mechanism has been suggested to illuminate the relationship between the preparation condition and the morphology of CeO2.

Experimental and theoretical investigations of Michelia alba leaves extract as a green highly-effective corrosion inhibitor for different steel materials in acidic solution

The aqueous Michelia alba leaf extract (MALE) was first evaluated as an inhibitor to the corrosion of different steel materials (industrial pure iron, stainless steel and carbon steel) in hydrochloric acid. The adsorption and corrosion inhibition of MALE were investigated by potentiodynamic polarization, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and quantum chemical calculations. The results showed that MALE acted as a highly-efficient mixed-type inhibitor for all steels and increasing temperatures benefited its corrosion inhibition. The adsorption of MALE on steel surfaces obeyed a Langmuir adsorption isotherm. Quantum chemical calculation results provided reasonable theoretical explanation for the inhibition property of MALE.

Environmental Friendly Corrosion Inhibitors for Magnesium Alloys

Magnesium is an important engineering material because of its light weight and excellent properties. Its density is 1.74 g⋅cm-3, only 2/3 that of aluminum and 1/4 that of iron. Moreover, it also has many advantageous properties such as good castability, hot formability, excellent machinability, good electromagnetic shielding characteristics, good biocompatibility, and recyclability (Cao et al, 2006; Staiger et al, 2006). Therefore, magnesium and its alloys have the potential to replace steel and aluminum in many applications. They have already been used in aerospace, aircraft, automotive, mobile electronics, biomaterials and other fields (Zhang & Zhang, 2004). However, there are some challenges for applications of magnesium and its alloys in a larger scale. The most important one is improving their poor corrosion resistance. Magnesium is a very active metal, and the standard potential of Mg2+/Mg is -2.356V (vs. N.H.E. at 25°C) (Bard & Faulkner, 2001). Therefore, magnesium and its alloys are extremely susceptible to corrosion, which can cause the decreased mechanical stability and unattractive appearance (Gray & Luan, 2002). To protect magnesium and its alloys from being corroded, the following techniques are frequently used (Zhang & Zhang, 2004): Conversion surface treatments, as chromating, phosphating, etc., Anodizing, Electroplating and electroless plating, Adding corrosion inhibitors. A great number of scientific studies have been devoted to the subjects of the first 3 techniques above (Song, 2005). But the last one, adding corrosion inhibitors has been seldom involved. Inhibitors are chemicals that react with a metallic surface, or the environment this surface is exposed to, giving the surface a certain level of protection (Roberge, 2000). For the metals widely employed in the industry such as iron, copper, zinc and aluminum, adding corrosion inhibitors is an effective and convenient method to decrease the corrosion rate. For magnesium and its alloys, there are very few publications on their corrosion inhibitors and only few inhibitors such as the salts of F(Song, 2005), Cr2O72(Song, 2006), 8hydroxyquinoline (Galio et al, 2010), and so on, are involved. Since Fand Cr2O72pollute the environment seriously, it is quite necessary to pay more attention to develop the environmental friendly corrosion inhibitors for magnesium and its alloys.

Preparation of highly dispersed carbon supported AuPt nanoparticles via a capping agent-free route for efficient methanol oxidation

A facile synthesis of carbon-supported bimetallic AuPt catalysts via a capping agent-free route is reported. The synthesized AuPt nanoparticles are well dispersed with a narrow size distribution ranging from 2.50 to 4.50 nm. Compared with commercial PtRu/C and Pt/C nanoparticles, the present AuPt/C catalysts exhibit distinctly superior activity for the methanol oxidation reaction with notable CO tolerance. Moreover, the composition-dependent catalytic activity of AuPt/C catalysts is observed, which follows the order Au2Pt1/C > Au1Pt1/C > Au1Pt2/C.

Coupling effects of strain on structural transformation and bandgap engineering in SnS monolayer

The anisotropy strain effects on black phosphorus and the IV–VI monolayer analogues have been widely investigated due to their potential applications in solar energy conversion and opto-electronics. Although the coupling effects of strain on structural and electronic properties might be important in flexible monolayer materials they were neglected in most cases. In this paper, we investigated the strain effect on the properties of SnS via strain induced potential energy surface and band profiles. Our first-principles calculations predict different types of low-dimensional phases under ununiformed biaxial strain of 19.09 N m−1, with either strain induced semiconductor–metal transitions, indirect–direct bandgap transitions or negative Poissons ratio. Our calculations suggest a new method to illuminate the strain effect beyond the axis direction, demonstrating that the coupling of strain effect plays an important role in the search for new properties for flexible materials and cannot be neglected.

Metal powder–pure water system for rational synthesis of metal oxide functional nanomaterials: a general, facile and green synthetic approach

Metal oxide (MO) nanomaterials have played a pivotal role in many fields. The general, facile and green approach for rational synthesis of MO nanomaterials is highly desirable. In this work, a simple approach via an ultrasonic-assisted preoxidation and a subsequent hydrothermal oxidation (UAPO–HO) of metal powders directly in pure water without using any other chemicals has been developed as a general synthetic route to prepare MO nanomaterials. Three representative MO nanomaterials (Mn3O4 nanorods, ZnO nanopellets, and Fe3O4 nanocubes) have been successfully synthesized by this UAPO–HO approach for the first time. The properties of the newly synthesized MO nanomaterials, such like Mn3O4 as an electrode material for supercapacitors, ZnO as an photocatalyst for degrading organic pollutants, and Fe3O4 as a magnetic catalyst for disposing antibiotics, are investigated, which demonstrate attractive performance in energy storage and environmental protection. The synthetic approach developed here has the significant advantages of being chemical-utility least, product-purity high, facile, green and mild, which offers a unique clue for synthesis of MO nanomaterials.

O-Vacancy-enriched NiO hexagonal platelets fabricated on Ni foam as a self-supported electrode for extraordinary pseudocapacitance

To enhance the capacitive property of NiO-based electrodes, O-vacancy-enriched NiO hexagonal platelets have been fabricated in situ on an Ni foam current collector by a facile hydrothermal treatment of Ni foam in a H2O2 aqueous solution and subsequent calcination in N2 atmosphere. Due to the self-grown nature and the abundant oxygen vacancies, the as-prepared self-supported NiO electrode showed extraordinary pseudocapacitance. The specific capacitance of the as-prepared NiO electroactive materials was 2495 F g−1 at a scan rate of 1 mV s−1 (∼97% of the theoretical value of NiO) and the capacitance retention was higher than 80% when the current density increased from 0.5 to 10 A g−1. DFT computational studies proved the vital role of oxygen vacancies in increasing the conductivity, electrochemical active sites and surface reactivity, which substantially account for the significantly high specific capacitance and rate capability. This study may further broaden the applications of NiO-based materials and boost the research on oxygen nonstoichiometry.