Tao Hang

Decoration of Micro-/Nanoscale Noble Metal Particles on 3D Porous Nickel Using Electrodeposition Technique as Electrocatalyst for Hydrogen Evolution Reaction in Alkaline Electrolyte

Micro-/nanoscale noble metal (Ag, Au, and Pt) particle-decorated 3D porous nickel electrodes for hydrogen evolution reaction (HER) in alkaline electrolyte are fabricated via galvanostatic electrodeposition technique. The developed electrodes are characterized by field emission scanning electron microscopy and electrochemical measurements including Tafel polarization curves, cyclic voltammetry, and electrochemical impedance spectroscopy. It is clearly shown that the enlarged real surface area caused by 3D highly porous dendritic structure has greatly reinforced the electrocatalytic activity toward HER. Comparative analysis of electrodeposited Ag, Au, and Pt particle-decorated porous nickel electrodes for HER indicates that both intrinsic property and size of the noble metal particles can lead to distinct catalytic activities. Both nanoscale Au and Pt particles have further reinforcement effect toward HER, whereas microscale Ag particles exhibit the reverse effect. As an effective 3D hydrogen evolution cathode, the nanoscale Pt-particle-decorated 3D porous nickel electrode demonstrates the highest catalytic activity with an extremely low overpotential of -0.045 V for hydrogen production, a considerable exchange current density of 9.47 mA cm(-2) at 25 °C, and high durability in long-term electrolysis, all of which are attributed to the intrinsic catalytic property and the extremely small size of Pt particles.

High-performance Si-based 3D Cu nanostructured electrode assembly for rechargeable lithium batteries

In this work, we report the synthesis of a Si/Cu nanocone-array (NCA) electrode via a facile ambient electrodeposition method with subsequent magnetron sputtering deposition. The close connection between the Cu NCA and the silicon layer facilitates the charge transfer in the system and supports a binder-free technique of preparing lithium ion battery (LIB) anodes. The void spaces between Si cylinders allow not only greater alleviation of the strain caused by the Si expansion during lithiation but also a significantly enhanced rate performance due to the increasing electrode/electrolyte contact area, and shortening path lengths for electronic and Li+ transport. Such engineered electrodes exhibit a long cycle life up to 2000 cycles and can be very promising for high-performance anode applications.

Preparation and characterization of nickel–cobalt alloy nanostructures array fabricated by electrodeposition

A series of Ni–Co alloy nanocones arrays were fabricated by means of electrodeposition method without using any template. The alloy nanocones crystallized in the face-centered cubic lattice structure and grew preferentially along directions. The aspect ratio of the alloy cones was found to increase with increasing cobalt content. The chemical potential difference of the solid–liquid interface and the synergistic effect of twinning were proposed to explain this phenomenon. By adjusting the electrodeposition conditions, the morphology and size of the alloy nanocrystal can be modulated. The crystal modifier plays an important role in controlling the step distance and the morphology of the spiral growth layer. These Ni–Co alloy nanocones arrays are expected to have significant potential applications in the fields of catalysis and magnetic storage.

Bioinspired Multifunctional Au Nanostructures with Switchable Adhesion

Inspired by the self-cleaning of cicada wings, well-aligned Au-coated Ni nanocone arrays (Au@Ni NAs) have been fabricated by a simple and cheap electrodeposition method. After surface modification of n-hexadecanethiol, self-cleaning can be realized on this long-lived superhydrophobic surface with extremely low adhesive force. Switchable adhesion is obtained on its complementary porous surface. The porous Au structure is fabricated by a geometric replica of the nanocone arrays. After the same surface modification, it shows superhydrophobicity with high adhesion. The different adhesive behaviors on the two lock-and-key Au structures are ascribed to their different contact modes with a water droplet. Combining the superhydrophobic properties of the two complementary structures, they can be used to transport precious microdroplets without any loss. The bioinspired periodic Au@Ni NAs can also be potentially employed as surface-enhanced Raman scattering (SERS) substrates due to its electromagnetic enhancement effect, especially at the tips of the nanocones. Thus, superhydrophobic, SERS, long-lived, self-cleaning, microtransportation functions are realized on the basis of the two surfaces.

Electrodeposition and characterization of copper nanocone structures

In this work, large-scale Cu nanocone arrays were synthesized by a one-step electrodeposition method without any template. The surface morphologies of Cu deposits prepared under different fabrication conditions have been observed. The as-prepared Cu nanocones grow preferentially along the direction. The formation mechanism of the nanocone structure can be explained by the screw dislocation driven growth theory. In addition, this electrodeposited Cu film with nanocone structure exhibits a superhydrophobic property after chemical modification.

Structural control of a cobalt nanocone array grown by directional electrodeposition

A metallic nanocone array by means of a directional electrodeposition method without any template is reported. With the crystallization modifier in the nickel electroplating solution, the cobalt conical structure can be deposited onto different metal substrates. The morphology of the nanocones can be controlled by changing the electroplating condition. The as-prepared Co nanocones grow preferentially along directions with very sharp tips. The conical structures are single crystalline without any disruption of the lattice planes. The growth mechanism is also briefly discussed.

Wetting Transition of the Caterpillar-Like Superhydrophobic Cu/Ni–Co Hierarchical Structure by Heat Treatment

Caterpillar-like hierarchical structured Cu/Ni-Co coatings were fabricated by a simple two-step method of combined electroless and electrodeposition. Both contact angles and sliding angles were measured to investigate the hydrophobicity after stearic acid modification. The results revealed the contact angle was as high as 165.5°(superhydrophobic), while the sliding angle was only 3.5°, which makes it very promising as self-cleaning material. Wetting transition from slippery hydrophobicity to sticky hydrophobicity happened upon heat treatment. The scanning electron microscopy (SEM) analysis disclosed the morphology change of the hierarchical structure during the heat treatment leading to the wetting state transition. Different models of wetting states were raised and calculated to provide further confirmation of the transition. The contact angle remained larger than 156° when the pH value ranged from 1 to 14 and the heat-treatment temperature was from 100 to 250 °C. Such hierarchical micronanostructure and its special hydrophobicity are expected to have practical application in industry.

Electrodeposition of High Density Silver Nanosheets with Controllable Morphologies Served as Effective and Reproducible SERS Substrates

Silver nanosheets with a nanogap smaller than 10 nm and high reproducibility were constructed through simple and environmentally friendly electrodeposition method on copper plate. The sizes of the nanogaps can be varied from around 7 to 150 nm by adjusting the deposition time and current density. The nanosheets with different nanogaps exhibited varied surface-enhanced Raman scattering (SERS) properties due to electromagnetic mechanism (EM). The optimized high density silver nanosheets with a nanogap smaller than 10 nm showed effective SERS ability with an enhanced factor as high as 2.0 × 10(5). Furthermore, the formation mechanism of the nanosheets during the electrodeposition process has been investigated by discussing the influence of boric acid and current density. This method has proved to be applicable on different metal substrates, which exhibits the potential to be widely used in different fields.

Tunable resistance switching in solution processed chromium-doped strontium titanate nanoparticles films

In this work, resistance switching behaviours in solution processed chromium (Cr)-doped strontium titanate (SrTiO3) films have been investigated. Undoped SrTiO3 film shows I-V characteristics of typical nonlinear resistor and no resistance hysteresis loops are observed. On the contrary, Cr-doped SrTiO3 films show stable and reversible hysteresis loops, which can be controlled by applying different voltage bias. Based on a series of characterization results, including X-ray diffraction (XRD), Raman and X-ray photoelectron spectroscopy (XPS), we infer that Ti4+ is substituted by Cr3+, giving rise to increased concentration of oxygen vacancies. Therefore, the observed resistance switching phenomenon is attributed to voltage driven oxygen vacancy migration. Furthermore, gradually decreased overall resistance is also realized under repeated sweeping cycles.

Three-Dimensional Hierarchical Nanostructured Cu/Ni–Co Coating Electrode for Hydrogen Evolution Reaction in Alkaline Media

In this work, three-dimensional hierarchical nickel–cobalt alloy coating for hydrogen evolution cathode was fabricated by electrodeposition processes. The coatings’ morphology evolves from sea cucumber-like nanostructure to caterpillar-like one with the increase of cobalt content. A large amount of nanometric “steps,” served as the active sites for hydrogen evolution reaction, were observed. According to Tafel polarization measurements, the exchange current density of the as-synthesized coating with hierarchical nanostructure was 21.9 times compared with that of flat nickel coating. In addition, the hierarchical coating also displayed good electrochemical stability from the galvanostatic test.