分类： 材料科学 >> 材料化学 提交时间： 2017-11-01
摘要： Doping additional ions into semiconductor is a potential strategy to modify the electronic structure of semiconductor materials. By using a highly reactive colloidal Cu clusters as doping precursor, we present here the successful doping of Cu ions into TiO2 nanocrystalline that simultaneously transformed from amorphous anodic TiO2 nanotubes during a dissolution and recrystallization process. The Cu-doped TiO2 nanoparticles (Cu-TNPs) film was characterized by X-ray diffraction, scanning and transmission electron microscopy and Raman spectroscopy. The Cu-TNPs show a rugby-like shape with exposed active {101}, {001} facets and the long-axis parallel to [001] lattice direction. The substitutional Cu2+ ions dopants in TiO2 nanocrystals caused the swelling of the crystalline unit cell. Such efficient doping design facilitate the improvement of nanostructured TiO2 as a potential biosensor for glucose molecules.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-10-31
摘要： Catalysts are the foundation of sustainable and renewable energies to address the depletion of natural fossil fuels problem. Because the catalysts’ activity is surface chemistry dependent, those “naked”, so-called ligand-free catalysts with more active sites exposing to the reactants are more preferable. With ligand-free, highly surface charged nanomaterials as the innate products, a newly emerging technique―laser synthesis and processing in liquids―is gaining increasing attention. The priority of laser-synthesized ligand-free metallic catalysts over chemically-synthesized counterparts has been confirmed by increasing groups through comparative studies on their catalytic activities. Besides the ligand-free metallic catalysts, this technique also excels at synthesis of bimetallic-alloy, core-shell and defect-rich semiconductor catalysts, and show good compatibility with other techniques (e.g., hydrothermal treatment and electrophoresis) to develop advanced catalysts such as ternary oxide, doped semiconductor, supported composite, nanoparticle-polymer matrix and film catalysts. Following the concept of why to choose, how to synthesize and where to use, in this review, we first introduce the advantages of this technique and the synthesized catalysts, secondly show how to develop complex catalysts using the laser-generated particles as the building blocks, and finally present the exciting application examples for photodegradation, water splitting and fuel cells.
分类： 材料科学 >> 材料化学 提交时间： 2017-11-01
摘要： We report a simple and environment-friendly route to prepare platinum/reduced graphene oxide (Pt/rGO) nanocomposites (NCs) with highly reactive MnOx colloids as reducing agents and sacrificial templates. The colloids are obtained by laser ablation of a metallic Mn target in graphene oxide (GO)-containing solution. Structural and morphological investigations of the as-prepared NCs revealed that ultrafine Pt nanoparticles (NPs) with an average size of 1.8 (± 0.6) nm are uniformly dispersed on the surfaces of rGO nanosheets. Compared with commercial Pt/C catalysts, Pt/rGO NCs with highly electrochemically active surface areas show remarkably improved catalytic activity and durability toward methanol oxidation. All of these superior characteristics can be attributed to the small particle size and uniform distribution of the Pt NPs, as well as the excellent electrical conductivity and stability of the rGO catalyst support. These findings suggest that Pt/rGO electrocatalysts are promising candidate materials for practical use in fuel cells.
分类： 材料科学 >> 材料化学 提交时间： 2017-11-01
摘要： Morphology control and impurity doping are two widely applied strategies to improve the electrochemical performance of nanomaterials. Herein, we report an environmentally friendly approach to obtain Co-doped Ni(OH)2 nanosheet networks using a laser-induced cobalt colloid as a doping precursor followed by an aging treatment in a hybrid medium of nickel ions. The shape and specific surface area of the doped Ni(OH)2 can be successfully adjusted by changing the concentration of sodium thiosulfate. Furthermore, a Co-doped Ni(OH)2 nanosheet network was further converted into Co-doped NiO with its pristine morphology retained via facile thermal decomposition in air. The structure and electrochemical performance of the as-prepared samples are investigated with scanning and transmission electron microscopy, energy dispersive x-ray analysis, x-ray diffraction, Fourier transform infrared spectroscopy, the nitrogen adsorption-desorption isotherm technique, and electrochemical measurements. The Co-doped Ni(OH)2 electrode shows an ultrahigh specific capacitance of 1421 F/g at a current density of 6 A/g, and a good retention level of 76% after 1000 cycles, in sharp contrast with only a 47% retention level of the pure Ni(OH)2 electrode at the same current density. In addition, the Co-doped NiO electrode exhibits a capacitance of 720 F/g at 6 A/g and 92% retention after 1000 cycles, which is also superior to those values for relevant pure NiO electrodes. The Co2+ partially substitutes for Ni2+ in the metal hydroxide and oxide, resulting in an increase of free holes in the valence band, and, therefore, enhancement of the p-type conductivity of Ni(OH)2 and NiO. Moreover, such novel mesoporous nanosheet network structures are also able to enlarge the electrode-electrolyte contact area and shorten the path length for ion transport. The synergetic effect of these two results is responsible for the observed ultrahigh pseudocapacitor performance.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-08-15
摘要： Great effort is made to maximize the surface area and expose active sites of a catalyst by distributing it over a suitable electronic conducting support. We present a design and eco-friendly construction of a two-dimensional Pt/SnO2/reduced-graphene-oxide (rGO) nanocomposite to study the strong metal-semiconductor-support interactions as candidate highly active and durable electrocatalyst. Distinctively, highly reactive SnOx nanoparticles (NPs) induced by laser ablation in liquids were used as a precursor to transform the graphene oxide (GO). Simultaneously, the initial amorphous-like SnOx further crystallized into SnO2 NPs, which were uniformly anchored onto rGO sheets. Afterward, the photo-excited electrons from semiconductor SnO2 were used as green reducing agents. Ultrafine Pt NPs with an average size of about 1–2 nm were in situ reduced and uniformly anchored on the surface of crystallized SnO2 NPs. Compared with the Pt/rGO catalysts without SnO2 modification, the prepared Pt/SnO2/rGO catalysts not only show larger electrochemical active surface area and higher catalytic activity toward methanol oxidation but also exhibit better tolerance toward CO and long-term cycle stability. The significantly enhanced electrochemical performance should be attributed to the uniformly dispersed Pt NPs with ultrafine size and the synergetic effect from the hybrid noble metal-semiconductor-carbon network components, which possess promising potential applications as electrocatalysts for methanol oxidation.
分类： 物理学 >> 交叉学科物理及相关领域的科学与技术 提交时间： 2018-03-30
摘要： Co-Ni layered double hydroxides (LDHs), as promising supercapacitor electrode materials with high specific capacity, have suffered poor rate property and cycle stability. By doping and topochemical oxidation of Ni ions is considered as efficivent rout to overcome these drawbacks. In this work, Ni3+ doped cobalt-nickel layered double hydroxides (Co-Ni-LDHs) were synthesized by pluse laser ablation of Ni taget in CoCl2 aqeous solution. The existence of Ni3+ ions doped in Co-Ni-LDHs decline the conductive resistance, and increase the mobility of surface charge and transfer rate of electrolyte. As a results, the Ni3+ doped Co-Ni-LDHs display a maximum specific capacitance of 2275 F/g and 1450 F/g at the current density of 1 A/g and 20 A/g, respectivly, indicating a high rate specific capacitance. Moreover, the capacitance retention is to be 80% after 1800 cycles at the current density of 6 A/g, manifesting good cycling stability of Ni3+ doped Co-Ni-LDHs.
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