Halide-Doping Effect of Strontium Cobalt Oxide Electrocatalyst and the Induced Activity for Oxygen Evolution in an Alkaline Solution

Perovskites of strontium cobalt oxyhalides having the chemical formulae Sr2CoO4-xHx (H = F, Cl, and Br; x = 0 and 1) were prepared using a solid-phase synthesis approach and comparatively evaluated as electrocatalysts for oxygen evolution in an alkaline solution. The perovskite electrocatalyst crystal phase, surface morphology, and composition were examined by X-ray diffraction, a scanning electron microscope, and energy-dispersive X-ray (EDX) mapping. The electrochemical investigations of the oxyhalides catalysts showed that the doping of F, Cl, or Br into the Sr2CoO4 parent oxide enhances the electrocatalytic activity for the oxygen evolution reaction (OER) with the onset potential as well as the potential required to achieve a current density of 10 mA/cm2 shifting to lower potential values in the order of Sr2CoO4 (1.64, 1.73) > Sr2CoO3Br (1.61, 1.65) > Sr2CoO3Cl (1.53, 1.60) > Sr2CoO3F (1.50, 1.56) V vs. HRE which indicates that Sr2CoO3F is the most active electrode among the studied catalysts under static and steady-state conditions. Moreover, Sr2CoO3F demonstrates long-term stability and remarkably less charge transfer resistance (Rct = 36.8 ohm) than the other oxyhalide counterparts during the OER. The doping of the perovskites with halide ions particularly the fluoride-ion enhances the surface oxygen vacancy density due to electron withdrawal away from the Co-atom which improves the ionic and electronic conductivity as well as the electrochemical activity of the oxygen evolution in alkaline solution.

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Nanostructured β−NiS Catalyst for Enhanced and Stable Electro−oxidation of Urea

Catalysts ◽

10.3390/catal10111280 ◽

2020 ◽

Vol 10 (11) ◽

pp. 1280

Author(s):

Tzu-Ho Wu ◽

Yan-Cheng Lin ◽

Bo-Wei Hou ◽

Wei-Yuan Liang

Keyword(s):

Photoelectron Spectroscopy ◽

Electrochemical Impedance ◽

Hydrothermal Reaction ◽

Charge Transfer Resistance ◽

Hydrogen Energy ◽

Transfer Resistance ◽

X Ray ◽

Onset Potential ◽

Slow Kinetics ◽

Electro Oxidation

Urea oxidation reaction (UOR) has received a high level of recent interest since electrochemical oxidation of urea can remediate harmful nitrogen compounds in wastewater and accomplish hydrogen fuel production simultaneously. Thus, urea is considered to be potential hydrogen energy source that is inherently safe for fuel cell applications. However, the catalytic reaction suffers from slow kinetics due to six electron transfer in UOR. In this work, β phase NiS is successfully prepared through facile hydrothermal reaction, in which diethanolamine (DEA) was added as chelating agent leading to 3D nanoflower morphology. The crystal structure, surface morphology, and chemical bonding of the β−NiS were characterized by X–ray diffraction (XRD), scanning electron microscope (SEM), and X−ray photoelectron spectroscopy (XPS), respectively. The UOR performance of NiS was evaluated by means of linear sweep voltammetry (LSV), Tafel analysis, electrochemical impedance spectroscopy (EIS), chronoamperometry, and chronopotentiometry in 1 M KOH electrolyte containing 0.33 M urea. Compared to the Ni(OH)2 counterpart, NiS exhibits lower onset potential, increased current responses, faster kinetics of urea oxidation, lower charge transfer resistance, and higher urea diffusion coefficient, leading to the enhanced catalytic performance toward UOR. Moreover, the developed NiS catalyst exhibits superior stability and tolerance towards urea electro−oxidation in 10,000 s test.

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An Efficient and Functional Fe3O4/Co3O4 Composite for Oxygen Evolution Reaction

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2021.19098 ◽

2021 ◽

Vol 21 (4) ◽

pp. 2675-2680

Author(s):

Adeel Liaquat Bhatti ◽

Umair Aftab ◽

Aneela Tahira ◽

Muhammad Ishaq Abro ◽

Riaz Hussain Mari ◽

...

Keyword(s):

Charge Transfer ◽

Cobalt Oxide ◽

Oxygen Evolution ◽

Composite Structure ◽

Oxygen Evolution Reaction ◽

Electrochemical Impedance ◽

Charge Transfer Resistance ◽

Active Surface Area ◽

Transfer Resistance ◽

Onset Potential

The design of efficient, stable, durable and noble metal free electro catalysts for oxygen evolution reaction (OER) are of immediate need, but very challenging task. In this study, iron induction into cobalt oxide (Co3O4) has resulted composite structure by wet chemical method. The iron impurity has brought an electronic disorder into Fe3O4/cobalt oxide composite thereby efficient oxygen evolution reaction is demonstrated. An addition of iron content into composite resulted the alternation of morphology from Nano rods to clusters of nanoparticles. The successive addition of iron into composite system reduced the onset potential of OER as compared to the pristine cobalt oxide. A Tafel slope of 80 mVdec-1 indicates the favorable oxygen evolution reaction kinetics on the sample 4. An over-potential of 370 mV is required to reach a 10 mAcm-2 current density which is acceptable for a nonprecious catalyst. The catalyst is highly durable and stable for 30 hours. Electrochemical impedance spectroscopy further provided a deeper insight on charge transfer resistance and sample 4 has low charge transfer resistance that supported the OER polarization curves. The sample 4 has more electrochemical active surface area of 393.5 cm2. These obtained results are exciting and highlighting the importance of composite structure and leave a huge space for the future investigations on composite materials for energy related applications.

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Influence of HAP on the Morpho-Structural Properties and Corrosion Resistance of ZrO2-Based Composites for Biomedical Applications

Crystals ◽

10.3390/cryst11020202 ◽

2021 ◽

Vol 11 (2) ◽

pp. 202

Author(s):

Réka Barabás ◽

Carmen Ioana Fort ◽

Graziella Liana Turdean ◽

Liliana Bizo

Keyword(s):

Electrochemical Impedance ◽

Artificial Saliva ◽

Synergetic Effect ◽

Composite Layer ◽

Charge Transfer Resistance ◽

Processing Route ◽

Dental Alloys ◽

Metallic Electrode ◽

Transfer Resistance ◽

X Ray

In the present work, ZrO2-based composites were prepared by adding different amounts of antibacterial magnesium oxide and bioactive and biocompatible hydroxyapatite (HAP) to the inert zirconia. The composites were synthesized by the conventional ceramic processing route and morpho-structurally analyzed by X-ray powder diffraction (XRPD) and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS). Two metallic dental alloys (i.e., Ni–Cr and Co–Cr) coated with a chitosan (Chit) membrane containing the prepared composites were exposed to aerated artificial saliva solutions of different pHs (i.e., 4.3, 5, 6) and the corrosion resistances were investigated by electrochemical impedance spectroscopy technique. The obtained results using the two investigated metallic dental alloys shown quasi-similar anticorrosive properties, having quasi-similar charge transfer resistance, when coated with different ZrO2-based composites. This behavior could be explained by the synergetic effect between the diffusion process through the Chit-composite layer and the roughness of the metallic electrode surface.

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Synthesis and Characterization of Electrodeposited C-PANI-Pd-Ni Composite Electrocatalyst for Methanol Oxidation

International Journal of Electrochemistry ◽

10.1155/2014/383892 ◽

2014 ◽

Vol 2014 ◽

pp. 1-8 ◽

Cited By ~ 9

Author(s):

S. S. Mahapatra ◽

S. Shekhar ◽

B. K. Thakur ◽

H. Priyadarshi

Keyword(s):

Methanol Oxidation ◽

Electrocatalytic Activity ◽

Electrochemical Impedance ◽

Synergistic Effects ◽

Catalytic Performance ◽

Charge Transfer Resistance ◽

Pani Film ◽

Composite Electrodes ◽

Transfer Resistance ◽

Onset Potential

Electropolymerization of aniline at the graphite electrodes was achieved by potentiodynamic method. Electrodeposition of Pd (C-PANI-Pd) and Ni (C-PANI-Ni) and codeposition of Pd-Ni (C-PANI-Pd-Ni) microparticles into the polyaniline (PANI) film coated graphite (C-PANI) were carried out under galvanostatic control. The morphology and composition of the composite electrodes were obtained using scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) techniques. The electrochemical behavior and electrocatalytic activity of the electrode were characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronoamperometric (CA) methods in acidic medium. The C-PANI-Pd-Ni electrode showed an improved catalytic performance towards methanol oxidation in terms of lower onset potential, higher anodic oxidation current, greater stability, lower activation energy, and lower charge transfer resistance. The enhanced electrocatalytic activity might be due to the greater permeability of C-PANI films for methanol molecules, better dispersion of Pd-Ni microparticles into the polymer matrixes, and the synergistic effects between the dispersed metal particles and their matrixes.

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Iron phosphide nanoparticles as an efficient electrocatalyst for the OER in alkaline solution

Journal of Materials Chemistry A ◽

10.1039/c6ta04025j ◽

2016 ◽

Vol 4 (25) ◽

pp. 9750-9754 ◽

Cited By ~ 83

Author(s):

J. Masud ◽

S. Umapathi ◽

N. Ashokaan ◽

M. Nath

Keyword(s):

Oxygen Evolution ◽

Alkaline Medium ◽

Alkaline Solution ◽

Current Density ◽

Exchange Current ◽

Exchange Current Density ◽

Iron Phosphide ◽

Onset Potential ◽

Low Overpotential

Ultrasmall FeP nanoparticles have been reported as an efficient oxygen evolution electrocatalyst in alkaline medium with low onset potential for oxygen evolution and require low overpotential to reach 10 mA cm−2 exchange current density.

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Effect of Zirconium Oxide Reinforcement on Microstructural, Electrochemical and Mechanical Properties of TiNi Alloy Produced Via Powder Metallurgy Route

Journal of Engineering Materials and Technology ◽

10.1115/1.4051308 ◽

2021 ◽

pp. 1-22

Author(s):

Syed Abbas Raza ◽

Muhammad Imran Khan ◽

Muhammad Ramzan Abdul karim ◽

Rashid Ali ◽

Muhammad Umair Naseer ◽

...

Keyword(s):

Electrochemical Impedance ◽

Passive Layer ◽

Charge Transfer Resistance ◽

Tini Alloy ◽

X Ray Diffraction ◽

Zro2 Content ◽

Transfer Resistance ◽

X Ray ◽

Conventional Sintering ◽

Layer Resistance

Abstract Equiatomic TiNi alloy composites, reinforced with 0, 5, 10 and 15 vol. % ZrO2, were synthesized using conventional sintering approach. Equiatomic TiNi pre-alloyed powder and ZrO2 powder were mixed in planetary ball mill for 6 hours followed by cold compaction and pressure-less sintering, respectively. The sintered density was found to vary inversely with the addition of ZrO2 content. The X-Ray diffraction spectra have shown the formation of multiple-phases which were resulted from the decomposition of the B19'and B2 phases of the equiatomic TiNi alloy due to the addition of ZrO2 and higher diffusion rate of Ni than that of Ti in the alloy composite. An increase in hardness was noted due to the addition of ZrO2, measured by micro and nanoindentation techniques. Potentiodynamic polarization scan revealed a 10% decrease in the corrosion rate of the composite containing 10 vol. % ZrO2. Electrochemical impedance spectroscopy results indicated an increase in passive layer resistance (Rcoat) due to the increase in charge transfer resistance (Rct) caused by the reduced leaching of ions from the surface.

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Graphene-Wrapped FeOOH Nanorods with Enhanced Performance as Lithium-Ion Battery Anode

NANO ◽

10.1142/s1793292021500053 ◽

2020 ◽

pp. 2150005

Author(s):

Meng Sun ◽

Zhipeng Cui ◽

Huanqing Liu ◽

Sijie Li ◽

Qingye Zhang ◽

...

Keyword(s):

High Performance ◽

Electrode Materials ◽

Electronic Conductivity ◽

Rate Capability ◽

Lithium Ion ◽

Extraction Process ◽

Hybrid Structure ◽

Charge Transfer Resistance ◽

Transfer Resistance ◽

Distinctive Structure

FeOOH nanorods (NRs) wrapped by reduced graphene oxide (rGO) were fabricated using a facile solvothermal method. When used as anode materials for lithium-ion batteries (LIBs), the FeOOH NRs/rGO composites show a higher capacity (490[Formula: see text]mAh g[Formula: see text] after 100 cycles at a current density of 100[Formula: see text]mA g[Formula: see text] and better rate capability than pure FeOOH NRs. The enhanced electrochemical performance can be ascribed to the hybrid structure of FeOOH and rGO. On one hand, the introduction of rGO can improve electronic conductivity and reduce charge-transfer resistance for electrode materials. On the other hand, the distinctive structure (FeOOH NRs surrounded by flexible rGO) can effectively buffer large volume change during the Li[Formula: see text] insertion/extraction process. Our work provides a feasible strategy to obtain high-performance LIBs.

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Nitrogen-Doped Graphene: The Influence of Doping Level on the Charge-Transfer Resistance and Apparent Heterogeneous Electron Transfer Rate

Sensors ◽

10.3390/s20071815 ◽

2020 ◽

Vol 20 (7) ◽

pp. 1815 ◽

Cited By ~ 4

Author(s):

Maria Coros ◽

Codruta Varodi ◽

Florina Pogacean ◽

Emese Gal ◽

Stela M. Pruneanu

Keyword(s):

Doping Level ◽

Transfer Rate ◽

Charge Transfer Resistance ◽

Electron Transfer Rate ◽

Transfer Resistance ◽

X Ray ◽

Nitrogen Doped ◽

Heterogeneous Electron Transfer ◽

Nitrogen Doped Graphene ◽

Doped Graphene

Three nitrogen-doped graphene samples were synthesized by the hydrothermal method using urea as doping/reducing agent for graphene oxide (GO), previously dispersed in water. The mixture was poured into an autoclave and placed in the oven at 160 °C for 3, 8 and 12 h. The samples were correspondingly denoted NGr-1, NGr-2 and NGr-3. The effect of the reaction time on the morphology, structure and electrochemical properties of the resulting materials was thoroughly investigated using scanning electron microscopy (SEM) Raman spectroscopy, X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), elemental analysis, Cyclic Voltammetry (CV) and electrochemical impedance spectroscopy (EIS). For NGr-1 and NGr-2, the nitrogen concentration obtained from elemental analysis was around 6.36 wt%. In the case of NGr-3, a slightly higher concentration of 6.85 wt% was obtained. The electrochemical studies performed with NGr modified electrodes proved that the charge-transfer resistance (Rct) and the apparent heterogeneous electron transfer rate constant (Kapp) depend not only on the nitrogen doping level but also on the type of nitrogen atoms found at the surface (pyrrolic-N, pyridinic-N or graphitic-N). In our case, the NGr-1 sample which has the lowest doping level and the highest concentration of pyrrolic-N among all nitrogen-doped samples exhibits the best electrochemical parameters: a very small Rct (38.3 Ω), a large Kapp (13.9 × 10−2 cm/s) and the best electrochemical response towards 8-hydroxy-2′-deoxyguanosine detection (8-OHdG).

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EFFECT OF TiO2 PARTICLES ON MICRO-HARDNESS, CORROSION, WEAR AND FRICTION OF Ni–P–TiO2 COMPOSITE COATINGS AT DIFFERENT ANNEALING TEMPERATURES

Surface Review and Letters ◽

10.1142/s0218625x15500821 ◽

2016 ◽

Vol 23 (01) ◽

pp. 1550082 ◽

Cited By ~ 12

Author(s):

PRASANNA GADHARI ◽

PRASANTA SAHOO

Keyword(s):

Wear Resistance ◽

Corrosion Resistance ◽

Composite Coatings ◽

Corrosion Current ◽

Xrd Analysis ◽

Charge Transfer Resistance ◽

Micro Hardness ◽

Transfer Resistance ◽

X Ray ◽

Annealing Temperatures

The present study investigates the effect of titania particles on the micro-hardness, wear resistance, corrosion resistance and friction of electroless Ni–P–TiO2 composite coatings deposited on mild steel substrates at different annealing temperatures. The experimental results confirmed that the amount of TiO2 particles incorporated in the coatings increases with increase in the concentration of particles in the electroless bath. In presence of TiO2 particles, hardness, wear resistance and corrosion resistance of the coating improve significantly. At higher annealing temperature, wear resistance increases due to formation of hard Ni3P phase and incorporation of titania particles in the coated layer. Charge transfer resistance and corrosion current density of the coatings reduce with an increase in TiO2 particles, whereas corrosion potential increases. Microstructure changes and composition of the composite coating due to heat treatment are studied with the help of scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDXA) and X-ray diffraction (XRD) analysis.

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From Allergens to Battery Anodes: Nature-Inspired, Pollen Derived Carbon Architectures for Room- and Elevated- Temperature Li-ion Storage

Scientific Reports ◽

10.1038/srep20290 ◽

2016 ◽

Vol 6 (1) ◽

Cited By ~ 22

Author(s):

Jialiang Tang ◽

Vinodkumar Etacheri ◽

Vilas G. Pol

Keyword(s):

Photoelectron Spectroscopy ◽

Electrochemical Impedance ◽

Lithium Ion ◽

Charge Transfer Resistance ◽

High Rate ◽

Energy Storage Devices ◽

Lithium Storage ◽

Transfer Resistance ◽

Carbonaceous Particles ◽

X Ray

Abstract The conversion of allergic pollen grains into carbon microstructures was carried out through a facile, one-step, solid-state pyrolysis process in an inert atmosphere. The as-prepared carbonaceous particles were further air activated at 300 °C and then evaluated as lithium ion battery anodes at room (25 °C) and elevated (50 °C) temperatures. The distinct morphologies of bee pollens and cattail pollens are resembled on the final architecture of produced carbons. Scanning Electron Microscopy images shows that activated bee pollen carbon (ABP) is comprised of spiky, brain-like and tiny spheres; while activated cattail pollen carbon (ACP) resembles deflated spheres. Structural analysis through X-ray diffraction and Raman spectroscopy confirmed their amorphous nature. X-ray photoelectron spectroscopy analysis of ABP and ACP confirmed that both samples contain high levels of oxygen and small amount of nitrogen contents. At C/10 rate, ACP electrode delivered high specific lithium storage reversible capacities (590 mAh/g at 50 °C and 382 mAh/g at 25 °C) and also exhibited excellent high rate capabilities. Through electrochemical impedance spectroscopy studies, improved performance of ACP is attributed to its lower charge transfer resistance than ABP. Current studies demonstrate that morphologically distinct renewable pollens could produce carbon architectures for anode applications in energy storage devices.

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