Ting Zhu

TiO2 Fibers Supported β-FeOOH Nanostructures as Efficient Visible Light Photocatalyst and Room Temperature Sensor

Hierarchical heterostructures of beta-iron oxyhydroxide (β-FeOOH) nanostructures on electrospun TiO2 nanofibers were synthesized by a facile hydrothermal method. This synthesis method proves to be versatile to tailoring of β-FeOOH structural design that cuts across zero-dimensional particles (TF-P), one-dimensional needles (TF-N) to two-dimensional flakes (TF-F). In addition, synthesizing such oxyhyroxide nanostructures presents the advantage of exhibiting similar functional performances to its oxides counterpart however, without the need to undergo any annealing step which leads to undesirable structural collapse or sintering. The as-prepared hierarchical heterostructures possess high surface area for dye adsorptivity, efficient charge separation and visible photocatalytic activity. Also, for the first time, hydrogen gas sensing has been demonstrated on β-FeOOH nanostructures at room temperature. The reported hierarchical heterostructures of β-FeOOH on TiO2 nanofibers afford multiple functions of photocatalysis and sensing which are highly promising for environment monitoring and clean up applications.

Shaped-controlled synthesis of porous NiCo2O4 with 1-3 dimensional hierarchical nanostructures for high-performance supercapacitors

Nickel/cobalt-based precursors (NCP) with 1-3 dimensional (1-3D) nanostructures were synthesized via a facile hydrothermal method. The as-prepared NCP were then transformed into porous NiCo2O4 materials by calcination at 300 °C in air for 3 hours. The morphologies of the calcined samples retained a porous texture after calcination, where various 1-3D hierarchical nanostructures, including 2D nanobelts, interconnected 2D nanosheets forming a 3D structure, 1D nanoneedles assembled into chestnuts and 3D nanosponges, were formed. The as-derived structures were then evaluated as electrode materials for supercapacitors in virtue of their high surface areas (99–134 m2 g−1). The results show that these porous NiCo2O4 materials exhibited promising pseudo-capacitance with good cycling performance. The nanosponge sample registered the highest specific capacitance of 832 F g−1 at a CV scan rate of 1 mV s−1 due to its unique structure and highest surface area.

In situ chemical etching of tunable 3D Ni3S2 superstructures for bifunctional electrocatalysts for overall water splitting

Three-dimensional (3D) nanomaterials are rendered with large specific surface areas as well as desired physicochemical, electrical and catalytic properties for a large variety of functional applications. In this work, 3D Ni3S2 superstructures (needle array and leaf pattern) were created on nickel foams (NFs) through an in situ chemical etching (ICE) method. This anisotropic growth involves chemical dissolution, in situ nucleation and re-deposition processes, which endows the as-fabricated Ni3S2 with large surface areas and warrants firm adhesion to the NF as well. Importantly, the Ni3S2@NF can directly serve as effective binder-free electrodes for hydrogen evolution reactions (HERs) and oxygen evolution reactions (OERs) from electrocatalytic water splitting.

Bifunctional 2D-on-2D MoO3 nanobelt/Ni(OH)2 nanosheets for supercapacitor-driven electrochromic energy storage

A hybrid composite that unifies multiple structural attributes is the key for improved functional device performance. Moreover, hierarchical and porous assembly of dissimilar constituent elements at various length scales and dimensionality is highly appropriate for mass transfer and surface/interfacial-dominated reactions. Here, we demonstrate solution processed 2D-on-2D hierarchical architecture of nanobelt core–nanosheets shell consisting of dissimilar transition metal composite. The defining benefits of such hetero-structured material design are short ion diffusion pathway of a thin 2D nanobelt core that is interfaced to large surface area and porous 2D nanosheets. Accordingly, an integrated energy system that delivers multiple functionalities, i.e. supercapacitive charge storage and electrochromic optical modulation, is investigated due to its attractive complementary energy storage and energy conservation capabilities. Consequently, bifunctional electrochromism–supercapacitive properties are demonstrated where desirable optical transmittance modulation and coloration efficiency properties in parallel with favorable pseudocapacitive storage and specific capacitance properties are simultaneously realized. Such an integrated energy system is anticipated to have a broad range of smart applications in buildings, automobiles and other emerging electronics needs.

Topotactic Consolidation of Monocrystalline CoZn Hydroxides for Advanced Oxygen Evolution Electrodes

We present a room temperature topotactic consolidation of cobalt and zinc constituents into monocrystalline CoZn hydroxide nanosheets, by a localized corrosion of zinc foils with cobalt precursors. By virtue of similar lattice orientation and structure coordination, the hybrid hydroxides amalgamate atomically without phase separation. Importantly, this inu2005situ growth strategy, in combination with configurable percolated nanosheets, renders a high areal density of catalytic sites, immobilized structures, and conductive pathways between the nanosheets and underlying foils-all of which allow monocrystalline CoZn hydroxide nanosheet materials to function as effective electrodes for electrochemical oxygen evolution reactions. This convenient and eco-friendly topotactical transformation approach facilitates high-quality single crystal growth with improved multiphase purity and homogeneity, which can be extended to other transition metals for the fabrication of advanced functional nanocomposites.

Outside‐In Recrystallization of ZnS–Cu1.8S Hollow Spheres with Interdispersed Lattices for Enhanced Visible Light Solar Hydrogen Generation

For the first time an earth-abundant and nontoxic ZnS-Cu(1.8) S hybrid photocatalyst has been engineered with well-defined nanosheet hollow structures by a template-engaged method. In contrast to conventional surface coupling and loading, the unique outside-in recrystallization promotes co-precipitation of ZnS and Cu(1.8) S into homogeneous interdispersed lattices, hence forming a hybrid semiconductor with visible responsive photocatalytic activity. The as-derived ZnS-Cu(1.8) S semiconductor alloy is tailored into a hierarchical hollow structure to provide readily accessible porous shells and interior spaces for effective ion transfer/exchange. Notably, this synergistic morphology, interface and crystal lattice engineering, aim towards the design of novel nanocatalysts for various sustainable environmental and energy applications.

Self-assembly formation of NiCo2O4 superstructures with porous architectures for electrochemical capacitors

Nickel cobalt oxides (NiCo2O4) superstructures with microsized flowers (MF), nanoflowers (NF), nanoneedles (NN), and nanospheres (NS) have been prepared by a facile self-assembly formation and subsequent conversion process. The various morphologies of the nickel cobalt precursors (NCP) are tuned by using different salts, solvents, surfactants and reaction temperatures. The as-obtained NCP can be readily converted to NiCo2O4 through an annealing process with their structures well retained. The electrochemical properties of the as-derived NiCo2O4 are assessed as the active electrode materials. The results indicate that the NiCo2O4 has exhibited promising pseudo-capacitive properties with high capacitance and good cycling stability. The NF has delivered the highest specific capacitance of 636 F g−1 (at a rate of 1 mV s−1) among all the four samples, showing its potential application for next generation electrochemical capacitors.

Facile synthesis of flower-like hierarchical NiCo2O4 microspheres as high-performance cathode materials for Li–O2 batteries

Development of efficient and cost-effective catalyst is one of the key issues for practical lithium–oxygen (Li–O2) batteries. Herein, we report a facile synthesis of flower-like hierarchical NiCo2O4 microspheres as an effective cathode catalyst for Li–O2 batteries. The synthesized NiCo2O4 microsphere consists of loosely interconnected nanopetals, which could simultaneously offer sufficient active sites, facilitate mass transfer of Li+/O2 and provide enough space for Li2O2 deposition. When employed as the cathode catalyst for Li–O2 batteries, a low discharge/charge voltage gap of 0.86 V can be obtained, much lower than previously reported results for NiCo2O4. Meanwhile, flower-like NiCo2O4 shows improved discharge capacity (3163 mA h g−1 at 0.08 mA cm−2) and better cycle stability (60 cycles at 500 mA h g−1 capacity limit) compared with NiCo2O4 nanoneedles and bare carbon cathode. The superior electrochemical performance of NiCo2O4, together with the facile fabrication approach, makes NiCo2O4 microspheres a promising candidate for Li–O2 batteries.

High-efficient electrocatalysts by unconventional acid-etching for overall water splitting

Recent advances in doping and heterostructuring based on earth-abundant two-dimensional nanoframeworks provide new possibilities in electrocatalysis. In this study, a novel, unconventional, one-step self-regulating acid-etching strategy was developed to prepare two-tiered hierarchical Fe-doped and Pt-decorated nickel hydroxide nanosheets selectively for efficient oxygen evolution and hydrogen evolution reactions. The combinatorial hydrolysis of Ni ions in a self-limiting acidic environment induces selective growth of disparate dimension nanosheets. The proposed strategy, avoiding multifold structural design challenges, delivers highly exposed active sites and robust catalyst/support interfaces. Moreover, the exquisite structure and synergetic heterostructure modulation afford kinetically favorable electrolyte mass transport, and gas bubble release. Consequently, the structurally well-designed and hetero-coordinated electrodes attest highly efficient oxygen evolution with a low Tafel slope of 70.6 mV dec−1 and overpotential of 300 mV at a current density of 10 mA cm−2, while it 30.4 mV dec−1 and 37 mV for hydrogen evolution, which rival performances of state-of-the-art electrocatalysts.

Nature-Inspired Design of Artificial Solar-to-Fuel Conversion Systems based on Copper Phosphate Microflowers.

Phosphates play significant roles in plant photosynthesis by mediating electron transportation and furnishing energy for CO2 reduction. Motivated by this, we demonstrate herein an artificial solar-to-fuel conversion system, involving versatile copper phosphate microflowers as template and titanium dioxide nanoparticles as host photocatalyst. The elaborate flowerlike architectures, coupled with a unique proton-reduction cycle from interchangeability of different species of orthophosphate ions, not only offer a 2D nanosheet platform for an optimal heterostructure interface but also effectively augment charge-carrier transfer, thereby contributing to enhanced photoactivity and hydrogen generation. These nature-inspired, phosphate-derived nanocomposites advance the synthesis of a large variety of functional materials, which holds great potential for photochemical, photoelectric and catalytic applications.