Jinyun Liao

Controlled synthesis of three-dimensional CoNi microstructures composed of single crystal CoNi nanoleaves

Three dimensional (3D) alloyed micro- and nanostructures composed of nanoscale subunits with regular and novel morphologies have received intensive attention due to their interesting physicochemical properties and wide applications in different areas. In this study, 3D CoNi microstructures consisting of well-defined CoNi nanoleaves are synthesized by a complexant-assisted wet-chemical reduction process free of any surfactant or template, which is suitable for large scale production. Elemental maps obtained by X-ray energy-dispersive spectroscopy (EDS) indicate that Co and Ni elements are homogenously distributed in the microstructures, verifying that the sample is an alloy rather than a mixture of Co and Ni. High resolution transmission electron microscopy (HRTEM) images and the selected area electron diffraction (SAED) pattern demonstrate the nanoleaves in the 3D microstructures are single crystals. Magnetic measurements at room temperature revealed that the as-prepared 3D CoNi microstructures exhibit a ferromagnetic property with a coercivity of 197.4 Oe, which is much higher than that of many CoNi micro- and nanostructures reported in recent literature. Based on the evolution of the morphology of the products with increasing reaction time, a possible formation mechanism is proposed to illustrate the growth of the CoNi microstructures.

Solid-state-reaction synthesis of cotton-like CoB alloy at room temperature as a catalyst for hydrogen generation

A novel room-temperature solid-state reaction is developed to synthesize cotton-like CoB alloy (CoBSSR) catalysts with a large specific surface area of 222.4m(2)g(-1). In the hydrolysis of ammonia borane catalyzed by the CoBSSR, the rate of hydrogen generation can reach 68.7mLmin(-1) with a turnover frequency (TOF) value of ca. 6.9Lhydrogenmin(-1)gcatalyst(-1) at 25°C. The TOF value is about 2 times as large as that of CoB alloy prepared by a regular solid-state reaction, which is also much higher than those of the CoB catalysts recently reported in the literature. The activation energy of the hydrolysis of ammonia borane catalyzed by the CoBSSR is as low as 22.78kJmol(-1), hinting that the CoBSSR possesses high catalytic activity, which may be attributed to the large specific surface area and the abundant porous structure. The high catalytic performance, good recoverability and low cost of the CoBSSR enable it to be a promissing catalyst condidate in the hydrolysis of ammonia borane for hydrogen production in commercial application.

Fabrication of a Ti-supported NiCo2O4 nanosheet array and its superior catalytic performance in the hydrolysis of ammonia borane for hydrogen generation

The development of low-cost nanocatalysts with high activity, high stability and good reusability towards the hydrolysis of chemical hydrides for hydrogen generation is of great importance and significance in the field of hydrogen energy. In this work, a Ti-supported NiCo2O4 thin film nanosheet array (NiCo2O4/Ti) is fabricated by a facile method, and its catalytic performance in the hydrolysis of ammonia borane for hydrogen production is investigated. It is found that the turnover frequency (TOF) of NiCo2O4/Ti can reach 50.1 mol H2 min−1 (mol catalyst)−1, which is the highest TOF value reported for noble-metal-free catalysts towards the hydrolysis of ammonia borane. The apparent activation energy of ammonia borane hydrolysis in the presence of the NiCo2O4/Ti catalyst is as low as ca. 17.5 kJ mol−1. More importantly, the NiCo2O4/Ti catalyst can retain ca. 90% of its original catalytic activity after 10 cycles, exhibiting much improved durability and reusability in contrast to many nanocatalysts recently reported in the literature. Its high catalytic activity and low-cost, together with its good durability and reusability, enable NiCo2O4/Ti to be a strong catalyst candidate for the hydrolysis of ammonia borane for hydrogen production in the practical applications.

An array of leaf-like Co3Ni microstructures with ferromagnetic properties, superhydrophobic properties and high catalytic performance in the hydrolysis of ammonia borane

In this work, a Cu foil supported array of leaf-like Co3Ni microstructures composed of well aligned nanorods was synthesized by a facile electroless process. It was found that the as-prepared Co3Ni array exhibited ferromagnetic properties with enhanced coercivity. The static contact angle of water on the surface of the Co3Ni array could reach 154.7°, indicating that the Co3Ni array displayed superhydrophobic properties. In addition, the as-prepared Co3Ni array showed high catalytic activity in the hydrolysis of ammonia borane for hydrogen generation. More importantly, the Co3Ni array catalyst still retained ca. 91% of its original catalytic activity after 6 cycles, exhibiting significantly improved recyclability and reusability in contrast to many nanocatalysts reported in the literature. The high catalytic performance, together with its ferromagnetic and superhydrophobic properties, makes the Co3Ni array a multifunctional material with wide applications in different areas.

Flowery Ni Microcrystals Consisting of Star-shaped Nanorods: Facile Synthesis, Formation Mechanism and Magnetic Properties

Flowerlike Ni microcrystals composed of star-shaped Ni nanorods with a diameter of ~200 nm were fabricated by a facile chemical reduction process, in which ethylenediamine tetraacetic acid sodium (EDTA) was used as complexant to assist in the formation of the flowery shape of the sample. The products were characterized by X-ray diffractometer, scanning electron microscopy, energy-dispersive X-ray spectroscopy and superconducting quantum interference device magnetometer. Scanning electron microscopy images indicated the typical size of the flowery Ni microcrystals was 2–3 μm and the length of the star-shaped Ni nanorods was in the hundreds of nanometers up to micron scale. The X-ray diffraction pattern showed the Ni microcrystals were present in the face-centred cubic phase and magnetic measurement results demonstrated the greatly enhanced coercivity of the sample (168.5 Oe) at room temperature. Based on the evolution of the structure and the morphology of products with increasing reaction time, a possible formation mechanism was proposed to illustrate the growth of the flower-like Ni architecture.

MnCo2O4 film composed of nanoplates: synthesis, characterization and its superior catalytic performance in the hydrolytic dehydrogenation of ammonia borane

Catalytic hydrolysis of ammonia borane is regarded as a safe and efficient way to produce hydrogen, which has received much attention in the fields of energy and catalysis. However, the development of heterogeneous catalysts with both high catalytic performance and low cost for this hydrolytic reaction is still a great challenge. In this work, we have developed a novel catalyst for the hydrolysis of ammonia borane, viz. a Ti-supported nanostructured MnCo2O4 film composed of nanoplates with a thickness of 10–20 nm, which is then characterized using an X-ray powder diffractometer, field emission scanning electron microscope, elemental mapping and X-ray photoelectron spectrometer. In the hydrolysis of ammonia borane catalyzed by the as-prepared nanostructured MnCo2O4 film, the turnover frequency can reach 24.3 molhydrogen min−1 molcat−1, which is much higher than those of most noble-metal-free catalysts reported in the literature. More importantly, the film catalyst can retain 96% of its original activity after 7 cycles, demonstrating its high stability and good reusability. Considering its high activity, good reusability and low cost, the nanostructured MnCo2O4 film can be a promising catalyst towards the hydrolytic dehydrogenation of ammonia borane for hydrogen production.

Ca0.5Mg0.5Co2O4 Nanosheets Comprised of Nanoparticles, Synthesis, Characterization and their Catalytic Activity in the Hydrolysis of Ammonia Borane for Hydrogen Production

Catalytic hydrolytic reaction of ammonia borane (AB) is regarded as safe and efficient way to produce hydrogen. However, the development of heterogeneous catalysts with both high catalytic performance and low cost for this hydrolytic reaction is still a great challenge. In this work, we have developed a novel catalyst for the hydrolysis of ammonia borane, Ca0.5Mg0.5Co2O4 nanosheets composed of nanoparticles, which was characterized by X-ray powder diffractometer, field emission scanning electron microscope, transmission electron microscope, and volumetric analyzer. In the AB hydrolysis, the hydrogen production rate will increase as the increase the NaOH dosage. At NaOH dosage of 1.6 g, the turnover frequency is 4.8 molhydrogen min -1 molcat . It is also found that a high catalyst dosage and a high reaction temperature are favorable for the fast hydrogen release from AB solution. Keywords-hydrogen production; ammonia borane; nanosheets; catalysis