scholarly journals Promoting Role of Amorphous Carbon and Carbon Nanotubes Growth Modes of Methane Decomposition in One-Pot Catalytic Approach

Catalysts ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1217
Author(s):  
Lifang Chen ◽  
Luis Enrique Noreña ◽  
Jin An Wang ◽  
Roberto Limas ◽  
Ulises Arellano ◽  
...  

We report the simultaneous production of hydrogen fuel and carbon nanotubes (CNTs) via methane dehydrogenation catalyzed with Ni/SBA-15. Most Ni nanoparticles (NPs) with size between 10 and 30 nm were highly dispersed on SBA-15 and most of them had a strong interaction with the support. At temperatures ranging from 500 to 800 °C, methane could be decomposed to release hydrogen with 100% selectivity at conversion between 51 and 65%. There was no CO or CO2 detectable in the reaction fluent. In the initial stage of the reaction, amorphous carbon and dehydrogenated methane species adsorbed on the Ni NPs promoted the CH4 decomposition. The amorphous carbon atoms were then transformed into carbon nanotubes which chiefly consisted of a multiwall structure and grew towards different orientations via a tip-growth or a base-growth modes, controlled by the interaction strength between the Ni NPs and the SBA-15 support. Reaction temperature affected not only methane conversion, but also the diffusion of carbon atoms on/in the Ni NPs and their precipitation at the interfaces. At higher temperature, bamboo-like CNTs or onion-like metal-encapsulated carbons were formed, mainly due to the rate of carbon atom formation greater than that of carbon precipitation for CNTs construction. The CNTs formation mechanisms are discussed and their growth modes under different conditions are proposed.

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Jong Won Choi ◽  
Seul Ki Youn ◽  
Hyung Gyu Park

This paper describes the morphology of carbon nanomaterials such as carbon nanotube (CNT), graphene, and their hybrid structure under various operating conditions during a one-step synthesisviaplasma-enhanced chemical vapor deposition (PECVD). We focus on the synthetic aspects of carbon hybrid material composed of heteroepitaxially grown graphene on top of a vertical array of carbon nanotubes, called carbon micronymphaea. We characterize the structural features of this unique nanocomposite by uses of electron microscopy and micro-Raman spectroscopy. We observe carbon nanofibers, poorly aligned and well-aligned vertical arrays of CNT sequentially as the growth temperature increases, while we always discover the carbon hybrids, called carbon micronymphaea, at specific cooling rate of 15°C/s, which is optimal for the carbon precipitation from the Ni nanoparticles in this study. We expect one-pot synthesized graphene-on-nanotube hybrid structure poses great potential for applications that demand ultrahigh surface-to-volume ratios with intact graphitic nature and directional electronic and thermal transports.


2015 ◽  
Vol 3 (8) ◽  
pp. 4716-4721 ◽  
Author(s):  
Guoxin Gao ◽  
Shiyao Lu ◽  
Bitao Dong ◽  
Zhicheng Zhang ◽  
Yuansuo Zheng ◽  
...  

Large-scale flat Fe3O4 nanosheets coated by an amorphous carbon overlayer (denoted as Fe3O4@C NSs) was prepared via a simple one-pot solution method. When evaluated as an electrode for LIBs, the as-prepared Fe3O4@C NSs hybrids exhibit highly enhanced lithium storage properties.


Carbon ◽  
2019 ◽  
Vol 141 ◽  
pp. 782-793 ◽  
Author(s):  
Markus Martincic ◽  
Sandra Vranic ◽  
Elzbieta Pach ◽  
Stefania Sandoval ◽  
Belén Ballesteros ◽  
...  

2017 ◽  
Vol 42 (21) ◽  
pp. 14439-14448 ◽  
Author(s):  
Limo He ◽  
Song Hu ◽  
Long Jiang ◽  
Syed Shatir A. Syed-Hassan ◽  
Yi Wang ◽  
...  

2001 ◽  
Vol 675 ◽  
Author(s):  
K. B. K. Teo ◽  
M. Chhowalla ◽  
G. A. J. Amaratunga ◽  
W. I. Milne ◽  
G. Pirio ◽  
...  

ABSTRACTIn order to utilise the full potential of carbon nanotubes/nanofibers, it is necessary to be able to synthesize well aligned nanotubes/nanofibres at desired locations on a substrate. This paper examines the preferential growth of aligned carbon nanofibres by PECVD using lithographically patterned catalysts. In the PECVD deposition process, amorphous carbon is deposited together with the nanotubes due to the plasma decomposition of the carbon feed gas, in this case, acetylene. The challenge is to uniformly nucleate nanotubes and reduce the unwanted amorphous carbon on both the patterned and unpatterned areas. An etching gas (ammonia) is thus also incorporated into the PECVD process and by appropriately balancing the acetylene to ammonia ratio, conditions are obtained where no unwanted amorphous carbon is deposited. In this paper, we demonstrate high yield, uniform, ‘clean’ and preferential growth of vertically aligned nanotubes using PECVD.


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