Carburization of Fe/Ni Catalyst for Efficient Growth of Single-Walled Carbon Nanotubes

Preparation and Bolometric Responses of MoS2 Nanoflowers and Multi-Walled Carbon Nanotube Composite Network

Due to their broadband optical absorption ability and fast response times, carbon nanotube (CNT)-based materials are considered promising alternatives to the toxic compounds used in commercial infrared sensors. However, the direct use of pure CNT networks as infrared sensors for simple resistance read-outs results in low sensitivity values. In this work, MoS2 nanoflowers are composited with CNT networks via a facile hydrothermal process to increase the bolometric performance. The thermal diffusivity (α) against temperature (T) is measured using the transient electro-thermal (TET) technique in the range of 320 K to 296 K. The α-T curve demonstrates that the composite containing MoS2 nanoflowers provides significant phonon scattering and affects the intertube interfaces, decreasing the α value by 51%. As the temperature increases from 296 K to 320 K, the relative temperature coefficient of resistance (TCR) increases from 0.04%/K to 0.25%/K. Combined with the enhanced light absorption and strong anisotropic structure, this CNT–MoS2 composite network exhibits a more than 5-fold greater surface temperature increase under the same laser irradiation. It shows up to 18-fold enhancements in resistive responsivity ((Ron − Roff)/Roff) compared with the pure CNT network for a 1550 nm laser at room temperature (RT).

Confined Fe Catalysts for High-Density SWNT Arrays Growth: a New Territory for Catalyst-Substrate Interaction Engineering

Great efforts have been devoted to searching for efficient catalytic systems to produce ultra-high density single-walled carbon nanotube (SWNT) arrays, which lay the foundation for future electronic devices. However, one major obstacle for realizing high-density surface-aligned SWNT arrays is the poor stability of metal nanoparticles in chemical vapor deposition catalytic processes. Recently, Trojan catalyst has been reported to yield unprecedented high-density SWNT arrays with 130 SWNTs per µm on the a-plane (11-20) of the sapphire substrate. Herein, a concept of catalyst confinement effect is put forward to revealing the secret of remarkable growth efficiency of SWNT arrays by Trojan catalyst. Combined experimental and theoretical studies indicate that confinement of catalyst nanoparticles on discrete a-plane strips plays a key role in stabilizing the small nanoparticles. The highly dispersive and active states of catalysts are maintained, which promote the growth of super-dense SWNT arrays. By rationally designing the substrate reconstruction process, large areas of dense SWNT arrays (130 SWNTs per µm) covering the entire substrate are obtained. This approach may provide novel ideas for the synthesis of various high-density 1D nanomaterials.

Single-Step Preparation of Ultrasmall Iron Oxide-Embedded Carbon Nanotubes on Carbon Cloth with Excellent Superhydrophilicity and Enhanced Supercapacitor Performance

Nanocomposites consisting of carbon materials and metal oxides are generally preferred as anodes in electrochemical energy storage. However, their low capacitance limits the achieved energy density of supercapacitors (SCs) in aqueous electrolytes. Herein, we propose a rapid combustion strategy to construct a novel electrode architecture-ultrasmall Fe₂O₃ anchoring on carbon nanotubes (FeO-CNT)-as a superhydrophilic and flexible anode for SCs. In 1 M Na₂SO₄ aqueous electrolyte, such an FeO-CNT-20 anode presents a high capacitance of 483.4 mF cm^-2 (326 F g^-1) at 1 mA cm^-2. The aqueous asymmetric supercapacitor devices (ASCs) assembled by FeO-CNT-20 and MnO₂ present a maximum operating potential of 2.0 V with a high areal energy density of 0.11 mWh cm^-2 at a power density of 0.5 mW cm^-2. The flexible solid-state ASCs display an energy density of 0.99 mWh cm^-3 at 14.3 mW cm^-3. The rapidly prepared FeO-CNT not only offers an attractive electrode for SCs but also would open up exciting new avenues to the rational design and large-scale preparation of Fe₂O₃-based nanocomposites for electrochemical energy storage.