Laser-driven coating of vertically aligned carbon nanotubes with manganese oxide from metal organic precursors for energy storage

Abstract

Carbon nanotubes-transition metal oxide systems are intensively studied due to their excellent properties for electrochemical applications. In this work, an innovative procedure is developed for the synthesis of vertically aligned multi-walled carbon nanotubes (VACNTs) coated with transition metal oxide nanostructures. VACNTs are grown by plasma enhanced chemical vapor deposition and coated with a manganese-based metal organic precursor (MOP) film based on manganese acetate solution. Subsequent UV pulsed laser irradiation induces the effective heating-decomposition of the MOP leading to the crystallization of manganese oxide nanostructures on the VACNT surface. The study of the morphology, structure and composition of the synthesized materials shows the formation of randomly oriented MnO crystals, with few nanometers in size, and to their alignment in hundreds of nm long filament-like structures, parallel to the CNT's long axis. Electrochemical measurements reveal a significant increase of the specific capacitance of the MnO-VACNT system (100 F g) as compared to the initial VACNT one (21 F g).

Boost of Charge Storage Performance of Graphene Nanowall Electrodes by Laser-Induced Crystallization of Metal Oxide Nanostructures

“…The D band appears when graphene shows structural defects such as sp 3 -bonds, vacancies or boundaries, activating the breathing mode of hexagonal carbon rings. On the other hand, the G band is associated with the sp 2 -bonded carbon atoms. , To determine the defects in the GNW material, the I (D) versus I (G) intensity ratio was obtained. Laser irradiation can provoke local phase transformations such as melting, vaporization, or recrystallization, and the increment of defects produces changes in the I (D)/ I (G) ratio.…”

“…These methods often comprise complex synthetic processes using toxic compounds or high-temperature annealing treatments for a long time and using special environments for controlled growth. ,, Alternatively, the laser processing technique is a versatile approach to fabricate advanced materials for a variety of applications that is able to accomplish surface treatments with high spatial resolution and high throughput. This technique has the capability to induce heating into the material reaching high temperatures in short times (ns), promoting extremely fast chemical reactions/structural changes in a variety of chemical environments. − Thus, the complex coupling of physical and chemical phenomena acting during the laser irradiation of materials can prompt nonconventional growth kinetics leading to the formation of a great variety of nanomaterials even out of the thermodynamic equilibrium. ,, Particularly, the direct laser irradiation of metal organic precursors revealed high potential for the development of advanced functional nanomaterials in the form of highly crystalline epitaxial films of complex oxides. − Furthermore, the laser-induced growth of crystalline MnO 2 and NiO nanostructures on vertically aligned carbon nanotubes has been already reported by the respective pulsed UV laser processing of the metal organic precursor or metal oxide nanoparticles films previously deposited onto the carbon nanotubes. , This versatile method, however, led to a nonhomogeneous distribution of nanostructures onto the carbon nanotubes and revealed a modest processing time (tens of minutes per centimeter square).…”

Super-Capacitive Performance of Manganese Dioxide/Graphene Nano-Walls Electrodes Deposited on Stainless Steel Current Collectors

“…In addition, 2D and D + G bands appear much weaker than for bare GNWs sample due to the presence of MnO 2 coating on the surface and edges of the nano-walls. No specific bands of MnO 2 are recorded, likely due to its low loading, low crystallinity, and/or small crystal size [30].…”

“…Different methods can be used to deposit and prepare MnO 2 , such as hydrothermal [26], sol gel methods [24,27], and electrodeposition [24,27,28]. In previous studies, we have demonstrated the excellent electrochemical performance of galvanostatically electrodeposited MnO 2 on vertically aligned carbon nanotubes (VACNTs) [28,29] as well as laser-coated MnO 2 -VACNTs [30]. In addition, there is a need to reduce overall costs of electrochemical devices by the use of cost-effective current collectors such as stainless-steel foil.…”

Laser processing of graphene and related materials for energy storage: State of the art and future prospects

“…Some thermally activated chemical reactions taking place under extreme conditions can be triggered on the surface of nanocarbon materials. As an example, the growth of inorganic nanostructures on CNT and rGO surfaces by direct laser irradiation of nanocarbon mixed with other precursors has been reported, leading to the formation of hybrid materials [112][113][114][115][116][117]. The laser-induced creation of structural defects and openended carbon atoms has allowed the nanowelding of graphene sheets to gold metal contacts at laser fluences below the ablation threshold of graphene [118].…”