We report a simple, versatile in situ transmission electron microscopy (TEM) approach for investigating the nucleation and growth mechanism of carbon nanotubes (CNTs), by which the composition, phase transition, and physical state of various catalysts can be clearly resolved. In our approach, catalyst nanoparticles (NPs) are placed in a multiwall CNT "tubular furnace" with two open ends, and a high temperature is obtained by Joule heating in the specimen chamber of a TEM. The carbon is supplied by electron irradiation-induced injection of carbon atoms. Comparative studies on the catalytic behavior of traditional iron oxide and recently discovered gold catalysts were performed. It was found that the growth of CNTs from iron oxide involves the reduction of FeO to FeC, nucleation and growth of CNTs from partially liquefied FeC, and finally the formation of elemental Fe when the growth stops. In contrast, while changes in shape, size, and orientation were also observed for the fluctuating Au NPs, no chemical reactions or phase transitions occurred during the nucleation of CNTs. These two distinct nucleation and growth processes and mechanisms would be valuable for the structure-controlled growth of CNTs by catalyst design and engineering. © 2013 American Chemical Society.

Daiming Tang    Chang Liu    Wanjing Yu    Lili li Zhang    Pengxiang Hou    Li Jin-Cheng    Feng Li    Yoshio Bandô    Dmitri Golberg    成会明    

ACS Nano

2014

The effect of sulfur on the catalytic nucleation and growth of single-wall carbon nanotubes (SWCNTs) from an iron catalyst was investigated in situ by transmission electron microscopy (TEM). The catalyst precursor of ferrocene and growth promoter of sulfur were selectively loaded inside of the hollow core of multiwall CNTs with open ends, which served as a nanoreactor powered by applying a voltage inside of the chamber of a TEM. It was found that a SWCNT nucleated and grew perpendicularly from a region of the catalyst nanoparticle surface, instead of the normal tangential growth that occurs with no sulfur addition. Our in situ TEM observation combined with CVD growth studies suggests that sulfur functions to promote the nucleation and growth of SWCNTs by forming inhomogeneous local active sites and modifying the interface bonding between catalysts and precipitated graphitic layers, so that carbon caps can be lifted off from the catalyst particle. © 2014 American Chemical Society.

Lili li Zhang    Pengxiang Hou    Shisheng Li    Shi Chao    Cong Hongtao    Chang Liu    成会明    

Journal of Physical Chemistry Letters

2014

We report the fabrication of a highly active nonstoichiometric SnO based counter electrode for dye-sensitized solar cells (DSSCs). The introduction of oxygen vacancies into SnO results in a much lower charge transfer resistance and a higher polarization current density. The solar energy conversion efficiency of the SnO based DSSCs is increased by 67%. © the Partner Organisations 2014.

Jian Pan    王连洲    余济美    Gang Liu    成会明    

Chemical Communications

2014

Chemical decoration of defects is an effective way to functionalize graphene and to study mechanisms of their interaction with environment. We monitored dynamic atomic processes during the formation of a rotary Si trimer in monolayer graphene using an aberration-corrected scanning-transmission electron microscope. An incoming Si atom competed with and replaced a metastable C dimer next to a pair of Si substitutional atoms at a topological defect in graphene, producing a Si trimer. Other atomic events including removal of single C atoms, incorporation and relocation of a C dimer, reversible C-C bond rotation, and vibration of Si atoms occurred before the final formation of the Si trimer. Theoretical calculations indicate that it requires 2.0 eV to rotate the Si trimer. Our real-time results provide insight with atomic precision for reaction dynamics during chemical doping at defects in graphene, which have implications for defect nanoengineering of graphene. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zhiqing Yang    Lichang Yin    Lee Jaekwang    任文才    成会明     叶恒强    Sokrates Pantelides    Stephen Pennycook    Matthew Chisholm   

Angewandte Chemie - International Edition

2014

A conceptual metallic/semiconducting TaB/TaO core/shell heterostructure exhibits a substantial improvement in photocatalytic hydrogen evolution rate under both UV and visible light. TaB plays a dual role in boosting the photocatalytic activity by extending the light-absorption range via efficient interfacial electronic modification and by promoting the separation and transfer of photoexcited charge carriers by using metallic TaB core as an electron collector. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Yang Yongqiang    Chenghua Sun    王连洲    Zhibo Liu    Gang Liu    Xiuliang Ma    成会明    

Advanced Energy Materials

2014

We report an aqueous lithium-sulfur battery based on aqueous dissolved LiS/LiS redox couple as the cathode, metallic lithium as the anode and LiTiAlPSiO (LATP) as the separator. A reversible specific capacity of up to 1030 mA h g is attained. Moreover, aqueous lithium-polysulfide batteries have a discharge potential of 2.53 V versus Li/Li.

Na Li    Zhe Weng    Wang Yarong    Feng Li    成会明     周豪慎   

Energy and Environmental Science

2014

A sandwich-structured composite, which contains an inner layer of C/SiC between two outer layers of C/SiC-ZrB-ZrC, was fabricated by a technique that involved rapid chemical vapor infiltration and precursor infiltration and pyrolysis. In both cyclic and single ablation conditions for one thousand seconds by an oxyacetylene flame, the composites exhibited good ablation-resistant properties and low strength reductions after ablation because of the introduction of a great amount of UHTCs into the outer layers and the small thickness of the ablation-affected area, respectively. The ablation rate and strength reduction in cyclic ablation were lower than those in single ablation. © 2013 Elsevier Ltd.

Hu Chenglong    Pang Shengyang    Tang Sufang    Wang Shijun    Huang Hongtao    成会明    

Corrosion Science

2014

One of the most attractive research areas in lithium-ion batteries (LIBs) is to design elaborate nanostructure of the electrode, which has been considered as keys to solve the problems such as the low energy density, slow lithium ion and electron transport, and the large volume change of electrode materials during cycling processes. Here, mesoporous CoO with controllable structures was directly grown on a graphene membrane by hydrothermal reaction followed by annealing treatment, and used as an integrated anode in LIBs without using metallic current collector, binder and conductive additive. The light graphene membrane as current collector with high electrical conductivity and stability contributes to the high energy density of LIBs. A mesoporous structure with enough space is beneficial to lithium ion diffusion and strain buffer of CoO during discharge/charge processes, rendering the electrodes high performance. The integrated electrode shows good rate capability and impressive cycling stability without capacity loss over 500 cycles under a high current density of 500 mA g. © 2014 Elsevier B.V. All rights reserved.

Lü Li    Guangmin Zhou    Shan Xuyi    Songfeng Pei    Feng Li    成会明    

Journal of Power Sources

2014

Carbon nanotube (CNT)- and graphene (G)-based transparent conductive films (TCFs) are two promising alternatives for commonly-used indium tin oxide-based TCFs for future flexible optoelectronic devices. This review comprehensively summarizes recent progress in the fabrication, properties, modification, patterning, and integration of CNT- and G-TCFs into optoelectronic devices. Their potential applications and challenges in optoelectronic devices, such as organic photovoltaic cells, organic light emitting diodes and touch panels, are discussed in detail. More importantly, their key characteristics and advantages for use in these devices are compared. Despite many challenges, CNT- and G-TCFs have demonstrated great potential in various optoelectronic devices and have already been used for some products like touch panels of smartphones. This illustrates the significant opportunities for the industrial use of CNTs and graphene, and hence pushes nanoscience and nanotechnology one step towards practical applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Jinhong Du    Songfeng Pei    Laipeng Ma    成会明    

Advanced Materials

2014

With the assistance of a ferroelectric field in PbTiO nanoplates, noble metals and metal oxides can be selectively deposited on the positively and negatively charged {001} facets of the nanoplates. Compared to PbTiO with randomly deposited reducing co-catalyst Pt particles, photocatalytic H evolution on PbTiO with Pt particles selectively deposited on the positively charged {001} facet is an order of magnitude better. This journal is © the Partner Organisations 2014.

Zhen Chao    Yu Jimmy C.    Gang Liu    成会明    

Chemical Communications

2014