Insight on the active sites of CoNi alloy embedded in N-doped carbon nanotubes for oxygen reduction reaction

Lowering the platinum group metal content of oxygen reduction reaction catalysts is among the most prevalent research focuses in the field. This target is herein approached through supported Pd(II) complexes. Starting from a commercial macrocycle, a new ligand is synthesized, its solution behavior and binding properties briefly explored (potentiometry, UV-Vis) and then used to prepare a new catalyst. A supramolecular approach is used in order to obtain homogeneous decoration of carbon nanotubes surfaces, fostering novel possibilities to access single-ion active sites. The novel catalyst is characterized through X-ray photoelectron spectroscopy and scanning transmission electron microscopy and its promising oxygen reduction reaction performance is evaluated via rotating ring-disk electrode and rotating disk electrode in half-cell studies.

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Identification of Efficient Active Sites in Nitrogen-Doped Carbon Nanotubes for Oxygen Reduction Reaction

The Journal of Physical Chemistry C ◽

10.1021/acs.jpcc.9b11090 ◽

2020 ◽

Vol 124 (16) ◽

pp. 8689-8696 ◽

Cited By ~ 1

Author(s):

Zhengyu Xu ◽

Ziyu Zhou ◽

Boyang Li ◽

Guofeng Wang ◽

Paul W. Leu

Keyword(s):

Carbon Nanotubes ◽

Oxygen Reduction Reaction ◽

Oxygen Reduction ◽

Active Sites ◽

Reduction Reaction ◽

Nitrogen Doped ◽

Nitrogen Doped Carbon

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Hydrothermal Carbon/Carbon Nanotube Composites as Electrocatalysts for the Oxygen Reduction Reaction

Journal of Composites Science ◽

10.3390/jcs4010020 ◽

2020 ◽

Vol 4 (1) ◽

pp. 20 ◽

Cited By ~ 1

Author(s):

Rafael G. Morais ◽

Natalia Rey-Raap ◽

Rui S. Costa ◽

Clara Pereira ◽

Alexandra Guedes ◽

...

Keyword(s):

Carbon Nanotubes ◽

Electrical Conductivity ◽

Oxygen Reduction Reaction ◽

Oxygen Reduction ◽

Ball Milling ◽

Active Sites ◽

Chemical Reactivity ◽

Carbon Composite ◽

Reduction Reaction ◽

Limiting Current

The oxygen reduction reaction is an essential reaction in several energy conversion devices such as fuel cells and batteries. So far, the best performance is obtained by using platinum-based electrocatalysts, which make the devices really expensive, and thus, new and more affordable materials should be designed. Biomass-derived carbons were prepared by hydrothermal carbonization in the presence of carbon nanotubes with different oxygen surface functionalities to evaluate their effect on the final properties. Additionally, nitrogen functional groups were also introduced by ball milling the carbon composite together with melamine. The oxygen groups on the surface of the carbon nanotubes favor their dispersion into the precursor mixture and the formation of a more homogenous carbon structure with higher mechanical strength. This type of structure partially avoids the crushing of the nanotubes and the carbon spheres during the ball milling, resulting in a carbon composite with enhanced electrical conductivity. Undoped and N-doped composites were used as electrocatalysts for the oxygen reduction reaction. The onset potential increases by 20% due to the incorporation of carbon nanotubes (CNTs) and nitrogen, which increases the number of active sites and improves the chemical reactivity, while the limiting current density increases by 47% due to the higher electrical conductivity.

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Activity and active sites of nitrogen-doped carbon nanotubes for oxygen reduction reaction

Journal of Applied Electrochemistry ◽

10.1007/s10800-012-0523-0 ◽

2013 ◽

Vol 43 (4) ◽

pp. 387-397 ◽

Cited By ~ 39

Author(s):

Altansukh Dorjgotov ◽

Jinhee Ok ◽

YuKwon Jeon ◽

Seong-Ho Yoon ◽

Yong Gun Shul

Keyword(s):

Carbon Nanotubes ◽

Oxygen Reduction Reaction ◽

Oxygen Reduction ◽

Active Sites ◽

Reduction Reaction ◽

Nitrogen Doped ◽

Nitrogen Doped Carbon

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Proposal of a Facile Method to Fabricate a Multi-Dope Multiwall Carbon Nanotube as a Metal-Free Electrocatalyst for the Oxygen Reduction Reaction

Sustainability ◽

10.3390/su14020965 ◽

2022 ◽

Vol 14 (2) ◽

pp. 965

Author(s):

Sara Bakhtavar ◽

Mehdi Mehrpooya ◽

Mahboobeh Manoochehri ◽

Mehrnoosh Karimkhani

Keyword(s):

Electron Microscopy ◽

Carbon Nanotubes ◽

Electron Transfer ◽

Low Temperature ◽

Oxygen Reduction Reaction ◽

Oxygen Reduction ◽

Active Sites ◽

Reduction Reaction ◽

Multiwall Carbon Nanotube ◽

Multiwall Carbon

In this study, a one-pot, low-temperature synthesis method is considered for the fabrication of heteroatom dope multiwall carbon nanotubes (MWCNT). Doped MWCNT is utilized as an effective electrocatalyst for oxygen reduction reaction (ORR). Single, double, and triple doping of boron, nitrogen and sulfur elements are utilized as the dopants. A reflux system with temperature of 180 °C is implemented in the doping procedure. Actually, unlike the previous studies in which doping on the carbon structures was performed using a furnace at temperatures above 700 °C, in this green and sustainable method, the triple doping on MWCNT is conducted at atmospheric pressure and low temperature. The morphology and structure of the fabricated catalysts were evaluated by Fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and Raman spectroscopy. According to the results, the nanoparticles were encapsulated in the carbon nanotubes. Aggregated clusters of the sulfur in the case of S-MWCNT are considerable. Cyclic voltammetry (CV), rotating disk electrode, linear sweep voltammetry (LSV), and chronoamperometry electrochemical tests are employed for assessing the oxygen reduction activity of the catalysts. The results illustrate that by using this doping method, the onset potential shifts to positive values towards the oxidized MWCNT. It can be deduced that by doping the N, B, and S atoms on MWCNTs, the defects in the CNT structure, which serve as active sites for ORR application, increase. The N/S/B-doped graphitic layers have a more rapid electron transfer rate at the electrode/electrolyte interface. Thus, this can improve the electrochemistry performance and electron transfer of the MWCNTs. The best performance and electrochemical activity belonged to the NB-MWCNT catalyst (−0.122 V vs. Ag/AgCl). Also, based on the results gained from the Koutecky–Levich (KL) plot, it can be said that the ORR takes place through the 4 e− pathway.

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Synergistic Effects of Active Sites’ Nature and Hydrophilicity on the Oxygen Reduction Reaction Activity of Pt-Free Catalysts

Nanomaterials ◽

10.3390/nano8090643 ◽

2018 ◽

Vol 8 (9) ◽

pp. 643 ◽

Cited By ~ 4

Author(s):

Mariangela Longhi ◽

Camilla Cova ◽

Eleonora Pargoletti ◽

Mauro Coduri ◽

Saveria Santangelo ◽

...

Keyword(s):

Electron Microscopy ◽

Carbon Nanotubes ◽

Oxygen Reduction Reaction ◽

Oxygen Reduction ◽

Photoelectron Spectroscopy ◽

Carbon Nanostructures ◽

Active Sites ◽

Active Material ◽

Reduction Reaction ◽

X Ray

This work highlights the importance of the hydrophilicity of a catalyst’s active sites on an oxygen reduction reaction (ORR) through an electrochemical and physico-chemical study on catalysts based on nitrogen-modified carbon doped with different metals (Fe, Cu, and a mixture of them). BET, X-ray Powder Diffraction (XRPD), micro-Raman, X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), Scanning Transmission Electron Microscopy (STEM), and hydrophilicity measurements were performed. All synthesized catalysts are characterized not only by a porous structure, with the porosity distribution centered in the mesoporosity range, but also by the presence of carbon nanostructures. In iron-doped materials, these nanostructures are bamboo-like structures typical of nitrogen carbon nanotubes, which are better organized, in a larger amount, and longer than those in the copper-doped material. Electrochemical ORR results highlight that the presence of iron and nitrogen carbon nanotubes is beneficial to the electroactivity of these materials, but also that the hydrophilicity of the active site is an important parameter affecting electrocatalytic properties. The most active material contains a mixture of Fe and Cu.

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