scholarly journals An Electrochemical Impedance Study of Alkaline Water Splitting Using Fe Doped NiO Nanosheets

Physchem ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 69-81
Author(s):  
Zhen Qiu ◽  
Yue Ma ◽  
Gunnar A. Niklasson ◽  
Tomas Edvinsson
Keyword(s):  
Charge Transfer ◽  
Water Splitting ◽  
Surface Coverage ◽  
Electrochemical Impedance ◽  
Electrochemical Process ◽  
Alkaline Media ◽  
Transfer Resistance ◽  
Alkaline Water ◽  
Nio Nanosheets ◽  
Inductive Behavior

Mixed nickel-iron (Ni-Fe) compounds have recently emerged as promising non-precious electrocatalysts for alkaline water splitting. The understanding of the charge-transfer mechanism involved in the multi-step Faradic reaction, however, is still limited for the overall electrochemical process. In this paper, electrochemical impedance spectroscopy (EIS) measurements of Fe incorporated Ni oxide nanosheets were used to study the reaction kinetics for both hydrogen (HER) and oxygen (OER) evolution reactions in alkaline media. Our results showed that Fe incorporation improves the catalytic property of NiO nanosheets because of the lower reaction resistance and faster intermediate transformations. Detailed EIS modeling enables a separation of the surface coverage relaxation from the charge transfer resistance, with an inductive behavior observed in the low-frequency range for HER, holding important information on the dominating reaction mechanism. For OER, the good agreement between the EIS experimental results and a model with an inductance loop indicated that similar inductive behavior would be determining the EIS response at very low frequencies. The physical significance of the elementary steps gives insight into the governing reaction mechanisms involved in the electron and hole charge transfer, as well as the inherent properties of catalysts and their surface coverage relaxation.

A self-supported amorphous Ni–P alloy on a CuO nanowire array: an efficient 3D electrode catalyst for water splitting in alkaline media

2018 ◽  
Vol 54 (19) ◽  
pp. 2393-2396 ◽  
Author(s):  
Bing Chang ◽  
Shuai Hao ◽  
Zhixiang Ye ◽  
Yingchun Yang
Keyword(s):  
Water Splitting ◽  
Nanowire Array ◽  
Cell Voltage ◽  
Alkaline Media ◽  
Core Shell ◽  
Alkaline Water ◽  
A Cell ◽  
Cuo Nanowire ◽  
A Current ◽  
3D Electrode

An amorphous Ni–P alloy shell electrodeposited on a CuO nanowire array to synergistically boost the catalytic activity toward alkaline water splitting is reported, and this core@shell CuO@Ni–P nanowire array is durable with a cell voltage of only 1.71 V reaching a current density of 30 mA cm−2 using a two-electrode configuration in an alkaline water electrolyzer.

Chemically Coupled Cobalt Oxide Nanosheets Decorated onto the Surface of Multiwall Carbon Nanotubes for Favorable Oxygen Evolution Reaction

2021 ◽  
Vol 21 (4) ◽  
pp. 2660-2667
Author(s):  
Abdul Qayoom Mugheri ◽  
Aneela Tahira ◽  
Umair Aftab ◽  
Adeel Liaquat Bhatti ◽  
Ramesh Lal ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Composite Material ◽  
Cobalt Oxide ◽  
Oxygen Evolution ◽  
Oxygen Evolution Reaction ◽  
Electrochemical Impedance ◽  
Multiwall Carbon Nanotubes ◽  
Alkaline Media ◽  
Transfer Resistance ◽  
Multiwall Carbon

Cobalt oxide has been widely investigated among potential transition metal oxides for the electrochemical energy conversion, storage, and water splitting. However, they have inherently low electronic conductivity and high corrosive nature in alkaline media. Herein, we propose a promising and facile approach to improve the conductivity and charge transport of cobalt oxide Co3O4 through chemical coupling with well-dispersed multiwall carbon nanotubes (MWCNTs) during hydrothermal treatment. The morphology of prepared composite material consisting of nanosheets which are anchored on the MWCNTs as confirmed by scanning electron microscopy (SEM). A cubic crystalline system is exhibited by the cobalt oxide as confirmed by the X-ray diffraction study. The Co, O, and C are the only elements present in the composite material. FTIR study has indicated the successful coupling of cobalt oxide with MWCNTs. The chemically coupled cobalt oxide onto the surface of MWCNTs composite is found highly active towards oxygen evolution reaction (OER) with a low onset potential 1.44 V versus RHE, low overpotential 262 mV at 10 mAcm-2 and small Tafel slope 81 mV dec-1. For continuous operation of 40 hours during durability test, no decay in activity was recorded. Electrochemical impedance study further revealed a low charge transfer resistance of 70.64 Ohms for the composite material during the electrochemical reaction and which strongly favored OER kinetics. This work provides a simple, low cost, and smartly designing electrocatalysts via hydrothermal reaction for the catalysis and energy storage applications.

MONITORED DEFORMATION BY POTENTIAL-INDUCED DEFECTS IN CH3(CH2)n−1SH SELF-ASSEMBLED MONOLAYERS ON GOLD: EIS STUDY OF CHAIN LENGTH EFFECT ON SUBDIFFUSION AND SAMs’ HETEROGENEITY

2019 ◽  
Vol 26 (10) ◽  
pp. 1950067 ◽  
Author(s):  
AHMED MOUGARI ◽  
MOKHTAR ZABAT ◽  
SMAIL BOUDJADAR
Keyword(s):  
Charge Transfer ◽  
Electrochemical Impedance ◽  
Defect Density ◽  
Charge Transfer Resistance ◽  
Electrical Circuit ◽  
Transfer Resistance ◽  
Low Frequencies ◽  
Interface Evolution ◽  
Impedance Measurements ◽  
Self Assembled

From the defects-free self-assembled organic layers (SAMs) of CH3([Formula: see text]SH molecules with short chain lengths ([Formula: see text]) electrodeposited on the (111) surface of monocrystalline gold previously prepared, monitored defects (pinholes) were potential-induced from cyclic partial reduction of SAMs at an appropriate potential. Electrochemical impedance measurements were in-situ conducted and [Fe(CN)6][Formula: see text] ions were used as probes for mass and charge transfer. Interface evolution was modeled with an equivalent electrical circuit containing two distinct constant-phase elements (CPEs). One is a generalized semi-infinite Warburg element in series with a charge transfer resistance attributed to subdiffusion phenomenon through leaky sublayers at low frequencies; the other CPE is used for characterizing the interface heterogeneity at medium and high frequencies. At low frequencies, electrochemical impedance measurements show subdiffusion phenomenon, which depends on the remaining sublayer and its thickness. When the defect density increases, diffusion tends to be ordinary, obeying the Fick’s law.

scholarly journals Electrochemical behaviour of poly(3,4-ethylenedioxytiophene) modified glassy carbon electrodes after overoxidation − the influence of the substrate on the charge transfer resistance

2018 ◽  
Author(s):  
Dora Zalka ◽  
Soma Vesztergom ◽  
Mária Ujvári ◽  
Gyözö Láng
Keyword(s):  
Charge Transfer ◽  
Glassy Carbon ◽  
Electrochemical Impedance ◽  
Electrochemical Behaviour ◽  
Mechanistic Explanation ◽  
Time Instant ◽  
Charge Transfer Resistance ◽  
Polymer Chains ◽  
Transfer Resistance ◽  
Impedance Measurements

<p class="PaperAbstract">Time dependence of the electrochemical impedance of an overoxidized glassy carbon|poly(3,4-ethylenedioxytiophene) (PEDOT)|0.1 mol·dm<sup>-3</sup> sulfuric acid (aq.) elec­trode has been investigated. To follow the changes occurring at the film/substrate interface after the overoxidation procedure, successive impedance measurements were carried out. Although the system is intrinsically nonstationary, the charge transfer resis­tance (R<sub>ct</sub>) cor<strong>­</strong>res<strong>­</strong>ponding to different time instants could be determined by using the so-called 4-dimensional analysis method. The same post-experimental mathematic­cal/ana­lytical procedure could be used also for the estimation of the charge transfer resistance corresponding to the time instant just after overoxidation of the PEDOT film. The increase of the charge transfer resistance of the overoxidized system with respect to that of the pristine electrode suggests that during overoxidation the electrochemical activity of the film decreases and the charge transfer process at the metal/film interface beco­mes more hindered. After the overoxidation procedure, when the electrode potential was held in the “stability region” (at E = 0.4 V vs. SSCE in the present case) the R<sub>ct</sub> decre­ased continuously with experiment time to a value somewhat higher than that of the pristine electrode.<strong> </strong>By comparing the properties of the GC|PEDOT|0.1 M H<sub>2</sub>SO<sub>4</sub> and the Au|PEDOT|0.1 M H<sub>2</sub>SO<sub>4</sub> electrodes a possible mechanistic explanation for the observed behavior has been proposed. This is based on the assumption that in the case of the GC|PEDOT|0.1 M H<sub>2</sub>SO<sub>4</sub> electrode two processes may occur simultaneously during the impedance measurements: (a) reduction of the oxidized surface of the GC substrate, including the reduction of the oxygen-containing surface functionalities and (b) read­sorption of the polymer chains (polymer chain ends) on the surface.<strong></strong></p>

scholarly journals Electrochemical Impedance Spectroscopy on the Performance Degradation of LiFePO4/Graphite Lithium-Ion Battery Due to Charge-Discharge Cycling under Different C-Rates

Energies ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 4507 ◽  
Author(s):  
Yusuke Abe ◽  
Natsuki Hori ◽  
Seiji Kumagai
Keyword(s):  
Charge Transfer ◽  
Electrochemical Impedance Spectroscopy ◽  
Impedance Spectroscopy ◽  
Electrochemical Impedance ◽  
Specific Capacity ◽  
Lithium Ion ◽  
Performance Degradation ◽  
Charge Transfer Resistance ◽  
Transfer Resistance ◽  
Charge Discharge

Lithium-ion batteries (LIBs) using a LiFePO4 cathode and graphite anode were assembled in coin cell form and subjected to 1000 charge-discharge cycles at 1, 2, and 5 C at 25 °C. The performance degradation of the LIB cells under different C-rates was analyzed by electrochemical impedance spectroscopy (EIS) and scanning electron microscopy. The most severe degradation occurred at 2 C while degradation was mitigated at the highest C-rate of 5 C. EIS data of the equivalent circuit model provided information on the changes in the internal resistance. The charge-transfer resistance within all the cells increased after the cycle test, with the cell cycled at 2 C presenting the greatest increment in the charge-transfer resistance. Agglomerates were observed on the graphite anodes of the cells cycled at 2 and 5 C; these were more abundantly produced in the former cell. The lower degradation of the cell cycled at 5 C was attributed to the lowered capacity utilization of the anode. The larger cell voltage drop caused by the increased C-rate reduced the electrode potential variation allocated to the net electrochemical reactions, contributing to the charge-discharge specific capacity of the cells.

Engineering the ABIO-BIO interface of neurostimulation electrodes using polypyrrole and bioactive hydrogels

2020 ◽  
Vol 92 (6) ◽  
pp. 897-907 ◽  
Author(s):  
Ankita Bhat ◽  
Alexa R. Graham ◽  
Hemang Trivedi ◽  
Matthew K. Hogan ◽  
Philip J. Horner ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Charge Density ◽  
Electrochemical Impedance ◽  
Inverse Correlation ◽  
Membrane Resistance ◽  
Charge Transfer Resistance ◽  
Foreign Body Response ◽  
Transfer Resistance ◽  
Cord Injury ◽  
Interfacial Impedance

AbstractFollowing spinal cord injury, the use of electrodes for neurostimulation in animal models has been shown to stimulate muscle movement, however, the efficacy of such treatment is impaired by increased interfacial impedance caused by fibrous encapsulation of the electrode. Sputter-deposited gold-on-polyimide electrodes were modified by potentiostatic electrodeposition of poly(pyrrole-co-3-pyrrolylbutyrate-conj-aminoethylmethacrylate): sulfopropyl methacrylate [P(Py-co-PyBA-conj-AEMA):SPMA] to various charge densities (0–100 mC/cm2) to address interfacial impedance and coated with a phosphoryl choline containing bioactive hydrogel to address biocompatibility at the ABIO-BIO interface. Electrodes were characterized with scanning electron microscopy (surface morphology), multiple-scan rate cyclic voltammetry (peak current and electroactive area), and electrochemical impedance spectroscopy (charge transfer resistance and membrane resistance). SEM analysis and electroactive area calculations identified films fabricated with a charge density of 50 mC/cm2 as well suited for neurostimulation electrodes. Charge transfer resistance demonstrated a strong inverse correlation (−0.83) with charge density of electrodeposition. On average, the addition of polypyrrole and hydrogel to neurostimulation electrodes decreased charge transfer resistance by 82 %. These results support the use of interfacial engineering techniques to mitigate high interfacial impedance and combat the foreign body response towards epidurally implanted neurostimulation electrodes.

Thermal transitions in hydrated layer-by-layer assemblies observed using electrochemical impedance spectroscopy

Soft Matter ◽  
2014 ◽  
Vol 10 (34) ◽  
pp. 6467-6476 ◽  
Author(s):  
Choonghyun Sung ◽  
Katelin Hearn ◽  
Jodie Lutkenhaus
Keyword(s):  
Charge Transfer ◽  
Electrochemical Impedance Spectroscopy ◽  
Impedance Spectroscopy ◽  
Electrochemical Impedance ◽  
Charge Transfer Resistance ◽  
Thermal Transition ◽  
Layer By Layer ◽  
Thermal Transitions ◽  
Transfer Resistance ◽  
Hydrated Layer

Layer-by-layer assemblies exhibit increased conductivity and decreased charge transfer resistance upon heating through the thermal transition.

BENIGN APPROACH OF CANTHIUM PARVIFLORUM AS A BIOINHIBITOR FOR MILD STEEL CORROSION IN 0.5 M H2SO4 MEDIUM

2020 ◽  
Vol 27 (09) ◽  
pp. 1950208
Author(s):  
K. A. KARTHICK ◽  
D. S. BHUVANESHWARI ◽  
D. UMAPATHI ◽  
PANDIAN BOTHI RAJA
Keyword(s):  
Charge Transfer ◽  
Mild Steel ◽  
Electrochemical Impedance ◽  
Measurement Techniques ◽  
Charge Transfer Resistance ◽  
Effect Of Temperature ◽  
Adsorption Model ◽  
Free Energy Of Adsorption ◽  
Transfer Resistance ◽  
Vis Spectroscopy

Canthium parviflorum leaf extract (CPLE) was utilized for corrosion prevention against mild steel (MS) in 0.5[Formula: see text]mol[Formula: see text]L[Formula: see text] H2SO4 test medium. Standard corrosion measurement techniques (gravimetric and electrochemical) were employed for this purpose. Gravimetric tests clearly confirmed that the prepared CPLE efficiently performs as corrosion inhibitor. Potentiodynamic polarization measurements (PPM) and electrochemical impedance spectroscopy (EIS) measurements were performed in order to analyze the charge transfer process of CPLE. Polarization curves indicate that CPLE acts through mixed mode inhibition. Impedance study reveals that the CPLE additives enhances the charge transfer resistance values and conversely decreases values of double layer capacitance. Scanning electron microscopy (SEM), Ultraviolet-Visible (UV-Vis) spectroscopy analysis and Fourier-Transform Infrared spectroscopy (FTIR) were done to confirm the Fe-CPLE complex formation on MS. The effect of temperature reveals that the inhibition efficiency increases with decrease in temperature and increase in concentration of CPLE (maximum of 4[Formula: see text]mg[Formula: see text]L[Formula: see text]). The adsorption of CPLE shows that it obeys Langmuir’s isotherm model with free energy of adsorption, [Formula: see text][Formula: see text]kJ mol[Formula: see text]. A suitable adsorption model is also proposed.

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