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

Nanomaterials ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 643 ◽  
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.

scholarly journals MOF-Derived CuPt/NC Electrocatalyst for Oxygen Reduction Reaction

Catalysts ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 799 ◽  
Author(s):  
Rehan Anwar ◽  
Naseem Iqbal ◽  
Saadia Hanif ◽  
Tayyaba Noor ◽  
Xuan Shi ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Photoelectron Spectroscopy ◽  
Rotating Disk ◽  
Reduction Reaction ◽  
Rotating Disk Electrode ◽  
X Ray ◽  
Onset Potential ◽  
Orr Activity

Metal-organic frameworks (MOFs) have been at the center stage of material science in the recent past because of their structural properties and wide applications in catalysis. MOFs have also been used as hard templates for the preparation of catalysts. In this study, highly active CuPt/NC electrocatalyst was synthesized by pyrolyzing Cu-tpa MOF along with Pt precursor under flowing Ar-H2 atmosphere. The catalyst was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray powder diffraction (XRD). Rotating disk electrode study was performed to determine the oxygen reduction reaction (ORR) activity for CuPt/NC in 0.1 M HClO4 at different revolutions per minute (400, 800, 1200, and 1600) and it was also compared with commercial Pt/C catalyst. Further the ORR performance was evaluated by K-L plots and Tafel slope. CuPt/NC shows excellent ORR performance with onset potential of 0.9 V (vs. RHE), which is comparable with commercial Pt/C. The ORR activity of CuPt/NC is demonstrated as an efficient electrocatalyst for fuel cell.

scholarly journals Multi-Walled Carbon Nanotubes Supported Pd(II) Complexes: A Supramolecular Approach towards Single-Ion Oxygen Reduction Reaction Catalysts

Energies ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5539
Author(s):  
Matteo Savastano ◽  
Maurizio Passaponti ◽  
Walter Giurlani ◽  
Leonardo Lari ◽  
Antonio Bianchi ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Photoelectron Spectroscopy ◽  
Active Sites ◽  
Platinum Group Metal ◽  
Reduction Reaction ◽  
Rotating Disk Electrode ◽  
Disk Electrode ◽  
Supported Pd

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.

scholarly journals Highly effective Fe-N-C electrocatalysts toward oxygen reduction reaction originated from 2,6-diaminopyridine

2021 ◽  
Author(s):  
Weixiang Yang ◽  
Shuihua Tang ◽  
Qiankuan Huang ◽  
Qian Zhang ◽  
Zhen Tang ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Photoelectron Spectroscopy ◽  
Active Sites ◽  
Cost Effective ◽  
Reduction Reaction ◽  
Limiting Current ◽  
X Ray ◽  
Onset Potential

Abstract Fe-N-C electrocatalysts have been intensively studied due to their extraordinary catalytic activity toward oxygen reduction reaction (ORR). Here we prepare a Fe-N-C electrocatalyst through cost-effective and nontoxic precursors of 2,6-diaminopyridine (DAP) and FeCl3, where iron ions react with DAP to formed Fe-Nx species first, followed by polymerization and pyrolysis. X-ray diffraction patterns display no obvious Fe2O3 peaks observed in the catalyst as the nominal content of iron addition is less than 10 wt%. X-ray photoelectron spectroscopy spectra indicate that the catalyst has rich pyridinic nitrogen, graphitic nitrogen and Fe-Nx species, which are considered as active sites for ORR. Therefore the catalyst demonstrates an excellent catalytic activity with an onset potential of about 0.96 V, half-wave potential of about 0.84 V, and a limiting current density of 5.8 mA cm-2, better than commercial Pt/C catalyst in an alkaline medium. Furthermore its stability is also much more excellent than that of Pt/C. This work provides a strategy to synthesize universal M-N-C catalysts.

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

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.

Probing the Oxygen Reduction Reaction Active Sites over Nitrogen-Doped Carbon Nanostructures (CNx) in Acidic Media Using Phosphate Anion

ACS Catalysis ◽  
2016 ◽  
Vol 6 (10) ◽  
pp. 7249-7259 ◽  
Author(s):  
Kuldeep Mamtani ◽  
Deeksha Jain ◽  
Dmitry Zemlyanov ◽  
Gokhan Celik ◽  
Jennifer Luthman ◽  
...  
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Carbon Nanostructures ◽  
Active Sites ◽  
Reduction Reaction ◽  
Phosphate Anion ◽  
Acidic Media ◽  
Nitrogen Doped ◽  
Nitrogen Doped Carbon

scholarly journals Metallic Organic Framework-Derived Fe, N, S co-doped Carbon as a Robust Catalyst for the Oxygen Reduction Reaction in Microbial Fuel Cells

Energies ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3846 ◽  
Author(s):  
Xiao Luo ◽  
Wuli Han ◽  
Han Ren ◽  
Qingzuo Zhuang
Keyword(s):  
Fuel Cells ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Microbial Fuel Cells ◽  
Active Sites ◽  
Reduction Reaction ◽  
Alkaline Media ◽  
X Ray ◽  
Co Doped ◽  
Organic Framework

Oxygen reduction reaction (ORR) provides a vital role for microbial fuel cells (MFCs) due to its slow reaction kinetics compared with the anodic oxidation reaction. How to develop new materials with low cost, high efficacy, and eco-friendliness which could replace platinum-based electrocatalysis is a challenge that we have to resolve. In this work, we accomplished this successfully by means of a facile strategy to synthesize a metallic organic framework-derived Fe, N, S co-doped carbon with FeS as the main phase. The Fe/S@N/C-0.5 catalyst demonstrated outstandingly enhanced ORR activity in neutral PBS and alkaline media, compared to that of commercial 20% Pt-C catalyst. Here, we started-up and operated two parallel single-chamber microbial fuel cells of an air cathode, and those cathode catalysts were Fe/S@N/C-0.5 and commercial Pt-C (20% Pt), respectively. Scanning electron microscopy (SEM) elaborated that the Fe/S@N/C-0.5 composite did not change the polyhedron morphology of ZIF-8. According to X-ray diffractometry(XRD) curves, the main crystal phase of the resulted Fe/S@N/C-0.5 was FeS. The chemical environment of N, S, and Fe which are anticipated to be the high-efficiency active sites of ORR for MFCs were investigated by X-ray photoelectron spectroscopic(XPS). Nitrogen adsorption/desorption techniques were used to calculate the pore diameter distribution. In brief, the obtained Fe/S@N/C-0.5 material exhibited a pronounced reduction potential at 0.861 V (versus Reversible Hydrogen Electrode(RHE)) in 0.1M KOH solution and –0.03 V (vs. SCE) in the PBS solution, which both outperform the benchmark platinum-based catalysts. Fe/S@N/C-0.5-MFC had a higher Open Circuit Voltage(OCV) (0.71 V), stronger maximum power density (1196 mW/m2), and larger output voltage (0.47 V) than the Pt/C-MFC under the same conditions.

Co3O4 Nanoparticles-Modified α-MnO2 Nanorods Supported on Reduced Graphene Oxide as Cathode Catalyst for Oxygen Reduction Reaction in Alkaline Media

NANO ◽  
2016 ◽  
Vol 11 (11) ◽  
pp. 1650126 ◽  
Author(s):  
GuanHua Jin ◽  
Suqin Liu ◽  
Yaomin Li ◽  
Yang Guo ◽  
Zhiying Ding
Keyword(s):  
Electron Microscopy ◽  
Graphene Oxide ◽  
Catalytic Activity ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Reduced Graphene Oxide ◽  
Reduction Reaction ◽  
Alkaline Media ◽  
X Ray ◽  
Reduced Graphene

Development of efficient electrocatalysts for the oxygen reduction reaction (ORR) remains a key issue for the commercialization of metal-air batteries. In this study, the novel structured Co3O4 nanoparticles-modified [Formula: see text]-MnO2 nanorods supported on reduced graphene oxide (Co3O4-MnO2/rGO) were synthesized with varying amounts of [Formula: see text]-MnO2 via a facile two-step hydrothermal method. The relationship between the physical properties and the electrochemical results was investigated using X-ray diffraction spectrum, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, cyclic voltammograms, electrochemical impedance spectroscopy and rotating disk electrode. The as-prepared Co3O4–MnO2 nanohybrid exhibits enhanced catalytic activity for ORR under alkaline condition compared with MnO2/rGO and Co3O4/rGO. Furthermore, it mainly favors a direct 4e-reaction pathway for ORR, which is attributed to the well-designed structure, the synergistic effect between Co3O4 and [Formula: see text]-MnO2, and the covalent coupling between the Co3O4-MnO2 and reduced graphene oxide. The role of Co3O4 in Co3O4–MnO2 hybrid for catalyzing ORR also has been illustrated by varying the mass ratio of Co3O4 and MnO2, which reveals that the Co3O4–MnO2 with the ratio of 1:1 has better catalytic activity.

High impact of the reducing agent on palladium nanomaterials: new insights from X-ray photoelectron spectroscopy and oxygen reduction reaction

RSC Advances ◽  
2016 ◽  
Vol 6 (15) ◽  
pp. 12627-12637 ◽  
Author(s):  
Yaovi Holade ◽  
Christine Canaff ◽  
Suzie Poulin ◽  
Têko W. Napporn ◽  
Karine Servat ◽  
...  
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Chemical Stability ◽  
Photoelectron Spectroscopy ◽  
Reduction Reaction ◽  
High Impact ◽  
Reducing Agent ◽  
X Ray ◽  
Catalytic Performances

The nature of the reduction agent changes drastically the palladium nanomaterials chemical stability, which subsequently alters earnestly their catalytic performances.

scholarly journals Galvanic Exchange as a Novel Method for Carbon Nitride Supported CoAg Catalyst Synthesis for Oxygen Reduction and Carbon Dioxide Conversion

Catalysts ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 860 ◽  
Author(s):  
Roshan Nazir ◽  
Anand Kumar ◽  
Sardar Ali ◽  
Mohammed Ali Saleh Saad ◽  
Mohammed J. Al-Marri
Keyword(s):  
Electron Microscopy ◽  
Carbon Dioxide ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Carbon Nitride ◽  
Reduction Reaction ◽  
Partial Replacement ◽  
Carbon Dioxide Conversion ◽  
X Ray ◽  
Bimetallic Alloy

A bimetallic alloy of CoAg nanoparticles (NPs) on a carbon nitride (CN) surface was synthesized using a galvanic exchange process for the oxygen reduction reaction (ORR) and carbon dioxide electrocatalytic conversion. The reduction potential of cobalt is ([Co2+(aq) + 2e− → Co(s)], −0.28 eV) is smaller than that of Ag ([Ag+(aq) + e− → Ag(s)], 0.80 eV), which makes Co(0) to be easily replaceable by Ag+ ions. Initially, Co NPs (nanoparticles) were synthesized on a CN surface via adsorbing the Co2+ precursor on the surface of CN and subsequently reducing them with NaBH4 to obtain Co/CN NP. The Co NPs on the surface of CN were then subjected to galvanic exchange, where the sacrificial Co atoms were replaced by Ag atoms. As the process takes place on a solid surface, only the partial replacement of Co by Ag was possible generating CoAg/CN NPs. Synthesized CoAg/CN bimetallic alloy were characterized using different techniques such as powder x-ray diffraction (PXRD), x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and electron diffraction spectroscopy (EDS) to confirm the product. Both the catalysts, Co/CN and CoAg/CN, were evaluated for oxygen reduction reaction in 1M KOH solution and carbon dioxide conversion in 0.5 M KHCO3. In the case of ORR, the CoAg/CN was found to be an efficient electrocatalyst with the onset potential of 0.93 V, which is comparable to commercially available Pt/C having Eonset at 0.91 V. In the electrocatalytic conversion of CO2, the CoAg/CN showed better performance than Co/CN. The cathodic current decreased dramatically below −0.9V versus Ag/AgCl indicating the high conversion of CO2.

Sign in / Sign up

Export Citation Format

Share Document