Wenxia Zhao

Porous Pt-Ni-P Composite Nanotube Arrays: Highly Electroactive and Durable Catalysts for Methanol Electrooxidation

Porous Pt-Ni-P composite nanotube arrays (NTAs) on a conductive substrate in good solid contact are successfully synthesized via template-assisted electrodeposition and show high electrochemical activity and long-term stability for methanol electrooxidation. Hollow nanotubular structures, porous nanostructures, and synergistic electronic effects of various elements contribute to the high electrocatalytic performance of porous Pt-Ni-P composite NTA electrocatalysts.

TiO2@C core–shell nanowires for high-performance and flexible solid-state supercapacitors

A flexible and solid-state supercapacitor device based on TiO2@C core–shell nanowires has been developed and exhibited excellent flexibility—it can even be folded and twisted without sacrificing electrochemical properties—and good electrochemical performance with a maximum energy density of 0.011 mW h cm−3.

Fe3O4/reduced graphene oxide with enhanced electrochemical performance towards lithium storage

In this work, we report the facile synthesis of Fe3O4/reduced graphene oxide (RGO) nanocomposites and their improved lithium storage capability. Fe3O4/RGO composites synthesized by a facile co-precipitation method exhibited outstanding electrochemical performance with good cycling stability. As an anode material for lithium ion batteries (LIBs), the Fe3O4/RGO composites achieved a high reversible capacity of 1637 mA h g−1 (0.1 A g−1) at the 10th cycle, which still remained at 1397 mA h g−1 after 100 cycles. Moreover, the Fe3O4/RGO composites have excellent rate capability. Characterization results reveal that such a large reversible capacity is attributed to the synergistic effect between Fe3O4 and RGO, with the Fe3O4 nanoparticles (NPs) with surface step atoms offering abundant electrochemical active sites for lithium storage. In addition, RGO acts as a volume buffer and electron conductor, and more importantly preserves the electrochemically active surface and avoids the aggregation of the Fe3O4 NPs.

Synthesis of long TiO2 nanowire arrays with high surface areas via synergistic assembly route for highly efficient dye-sensitized solar cells

Vertically aligned single crystal TiO2 nanowire arrays grown on transparent conductive substrates are of considerable interest for use as photoanodes in dye-sensitized solar cells because they can provide direct pathways that ensure the rapid collection of charge carriers generated throughout the cells. However, growth of TiO2 nanowire arrays on conductive glass with the combined characteristics of a large surface area and lengths up to tens of micrometers is still challenging and desirable for highly efficient solar cells. Here, we reported a mild hydrothermal approach for growing vertically aligned TiO2 nanowire arrays directly on conductive glass via the synergistic interaction of the octanoic acid and titanium trichloride. The resulting single crystal TiO2 nanowire arrays possess a large surface area of 95 m2 g−1 and a controlled length in the range of 6–46 μm. By applying 9.6 μm-long nanowire arrays in dye-sensitized solar cells, an overall photoconversion efficiency of 5.13% is achieved under a white light illumination of 100 mW cm−2.

Constructing hierarchical submicrotubes from interconnected TiO2 nanocrystals for high reversible capacity and long-life lithium-ion batteries

Here, we report a facile hydrothermal approach for synthesizing anatase TiO2 hierarchical mesoporous submicrotubes (ATHMSs) with the aid of long-chain polymer as soft template. The TiO2 nanocrystals, with sizes of 6–8 nm, are well interconnected with each other to build tubular architectures with diameters of 0.3–1.5 μm and lengths of 10–25 μm. Such highly porous structures give rise to very large specific surface area of 201.9 m2 g−1 and 136.8 m2 g−1 for the as-prepared and annealed samples, respectively. By using structurally stable ATHMSs as anode materials for lithium-ion batteries, they exhibited high reversible capacity, long cycling life and excellent cycling stability. Even after 1000 cycles, such ATHMS electrodes retained a reversible discharge capacity as high as 150 mAh g−1 at the current density of 1700 mA g−1, maintaining 92% of the initial discharge capacity (163 mAh g−1).

Cost-Effective Alkaline Water Electrolysis Based on Nitrogen- and Phosphorus-Doped Self-Supportive Electrocatalysts

Water splitting into hydrogen and oxygen in order to store light or electric energy requires efficient electrocatalysts for practical application. Cost-effectiveness, abundance, and efficiency are the major challenges of the electrocatalysts. Herein, this paper reports the use of low-cost 304-type stainless steel mesh as suitable electrocatalysts for splitting of water. The commercial and self-support stainless steel mesh is subjected to exfoliation and heteroatom doping processes. The modified stainless steel electrocatalyst displays higher oxygen evolution reaction property than the commercial IrO2 , and comparable hydrogen evolution reaction property with that of Pt. More importantly, an all-stainless-steel-based alkaline electrolyzer (denoted as NESSP//NESS) is designed for the first time, which possesses outstanding stability along with lower overall voltage than the conventional Pt//IrO2 electrolyzer at increasing current densities. The remarkable electrocatalytic properties of the stainless steel electrode can be attributed to the unique exfoliated-surface morphology, heteroatom doping, and synergistic effect from the uniform distribution of the interconnected elemental compositions. This work creates prospects to the utilization of low-cost, highly active, and ultradurable electrocatalysts for electrochemical energy conversion.

Facile Fabrication of Hierarchical SnO2 Microspheres Film on Transparent FTO Glass

Hierarchical SnO(2) microspheres consisting of nanosheets on the fluorine-doped tin oxide (FTO) glass substrates are successfully prepared via a facile hydrothermal synthesis process. The as-prepared novel microsphere films were characterized in detail by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy. Moreover, SnO(2) nanoparticles with 30-80 nm in size covered on the surface of nanosheets/microspheres were also obtained by optimizing the hydrothermal reaction temperature, time, or volume ratio of acetylacetone/H(2)O. The detailed investigations disclose the experimental parameters, such as acetylacetone, NH(4)F, and seed layer play important roles in the morphology of hierarchical SnO(2) microspheres on the FTO glass. The formation process of SnO(2) microspheres is also proposed based on the observations of time dependent samples.

Hierarchical Pd-Sn Alloy Nanosheet Dendrites: An Economical and Highly Active Catalyst for Ethanol Electrooxidation

Hierarchical alloy nanosheet dendrites (ANSDs) are highly favorable for superior catalytic performance and efficient utilization of catalyst because of the special characteristics of alloys, nanosheets, and dendritic nanostructures. In this paper, we demonstrate for the first time a facile and efficient electrodeposition approach for the controllable synthesis of Pd-Sn ANSDs with high surface area. These synthesized Pd-Sn ANSDs exhibit high electrocatalytic activity and superior long-term cycle stability toward ethanol oxidation in alkaline media. The enhanced electrocataytic activity of Pd-Sn ANSDs may be attributed to Pd-Sn alloys, nanosheet dendrite induced promotional effect, large number of active sites on dendrite surface, large surface area, and good electrical contact with the base electrode. Because of the simple implement and high flexibility, the proposed approach can be considered as a general and powerful strategy to synthesize the alloy electrocatalysts with high surface areas and open dendritic nanostructures.

Growth of vertically aligned MoS2 nanosheets on a Ti substrate through a self-supported bonding interface for high-performance lithium-ion batteries: a general approach

A promising new concept is to apply additive/binder-free electrodes for lithium-ion batteries by directly growing active materials on current collectors, however, they still suffer from the low quality electronic contact and poor mechanical stability due to the lattice mismatch between active materials and substrates. Here we present the direct growth of vertically aligned MoS2 nanosheets on a Ti substrate through a self-supported TiO2 bonding interface route, thereby preferentially exposing the edges on the film surface. In this unique structure, MoS2 nanosheets are interconnected with each other and create a strong adhesion to the Ti substrate through the TiO2 bonding interface, which would allow electrons to easily transport throughout the whole electrode. Furthermore, their edge-terminated structure can provide more sites for Li-ion intercalation. By using this additive/binder-free electrode, it can deliver a discharge capacity as high as 1189 mA h g−1 at a current density of 1000 mA g−1 after 600 cycles. Importantly, our synthetic approach, based on this metal surface dissolution–crystallization produced bonding interface, can provide a general strategy for the direct growth of other metal sulphides such as NiS and CoS nanosheets on the Ti substrate with great promise for various applications.

Polyhedral Fe3O4 nanoparticles for lithium ion storage

Ferroferric oxide, Fe3O4, is a highly promising anode material for lithium-ion batteries (LIBs) owing to its excellent electrochemical properties. High resolution transmission electron microscopy (HRTEM) was used to correlate the morphological features of the Fe3O4 nanoparticles (NPs) with their electrochemical properties. The co-precipitately synthesized Fe3O4 NPs were composed of 14-facet truncated octahedrons containing 6 {100} and 8 {111} planes, and 26-facet polyhedrons containing 6 {100}, 12 {110} and 8 {111} planes, indicating that the shape of NPs is changeable from 14-facet truncated octahedrons to 26-facet polyhedrons. As the anode for LIBs, the NPs delivered a high initial discharge capacity of 1067 mA h g−1, which could be attributed to their small size and abundant exposure of edges and corners in the multi-faceted polyhedral structures, offering low-coordinated atoms that act as active sites for lithium storage.