Double Layer Capacitance Values Research Articles

Construction of honeycomb-like N-doped porous carbon framework with effective aperture distribution toward advanced supercapacitors and sodium-ion batteries

Smart synthesis of porous carbon with appropriate aperture distribution and high area utilization still retains an enormous challenge for efficient charge storage. Herein, a simple freeze-drying along with subsequent one-step carbonization/activation process is ingeniously devised to fabricate honeycomb-like nitrogen-doped porous carbon (NPC) framework with high-level active N/O-functional groups and hierarchical porous structure including substantial ultra-micropores (<0.7 nm). The underlying formation mechanism of such porous NPC framework is tentatively proposed. By finely regulating the dosage of NaHCO3, the optimized NPC (i.e., NPC114) is endowed with ultra-high surface area utilization of ∼26.4 μF cm−2 at 1 A/g in KOH electrolyte, which is close to theoretical value of electrochemical double-layer capacitance (15–25 μF cm−2), and even larger than the case (∼22.4 μF cm−2) with H2SO4 electrolyte due to the inaccessible ultra-micropores by SO42− of larger size. Similarly, as for the organic system, the as-prepared NPC115 with higher meso- and macropore surface area exhibits higher energy density of 22.36 Wh kg−1 than other counterparts. Furthermore, NPC114, when evaluated as anode material for sodium-ion batteries, exhibited more attractive high-rate Na+-storage properties as well. The in-depth understanding into intrinsic relationship between aperture distribution and electrochemical behaviors will provide meaningful guidance for electrode material design

Passivation of the positive electrode during the discharge of Li-O2 and O2-assisted Li-CO2 batteries: A comparative study

The effect of passivation of the positive electrode by solid products under discharge is assessed for the first time as one of the factors determining the discharge characteristics of Li-O2 (LOB) and oxygen-assisted Li-CO2 (LCOB) batteries. In order to estimate the passivation, the electrode surface coverage θ by the reaction product (Li2O2 or Li2CO3) is determined on the basis of a decrease in the double-layer capacitance value in the course of the discharge. It is shown that for a given amount of electricity, the electrode surface coverage by Li2CO3 in LCOB is 1.5–2 times that of the coverage by Li2O2 under discharge in LOB. Furthermore, for each of the batteries, achievement of the maximum discharge capacity does not result in the full electrode surface blocking by the discharge products. LCOB manifests higher discharge characteristics than LOB under the kinetic reaction control (in the 100–500 mA g−1 current density range), owing to the accelerated conversion of intermediates and slower solid reaction product deposition on a larger electrode surface area. As the current density increases from 500 to 2000 mA g−1, the discharge capacity of LOB and LCOB decreases, which is mainly due to the effect of diffusion limitations. Moreover, while in the case of LOB the parameter θ decreases, in the case of LCOB it is practically independent of the current density in the studied range. The latter effect may be due to increased passivating properties of Li2CO3 deposits formed under high current density. The results of the work allow considering θ as a new criterion for estimation of the discharge depth and for predicting the characteristics of LCOB and LOB.

Sulfur-Phosphorus Doped Metal Composites As Superior Catalyst for Electrolytic Hydrogen Production in Real Seawater

In the face of the increasingly severe global energy crisis and challenges posed by climate change, promoting energy transition has become an international consensus. Among various renewable energy sources, hydrogen is considered an ideal energy carrier due to its clean and efficient characteristics. The electrolysis of seawater for hydrogen production has garnered widespread attention for its ability to fully utilize abundant seawater resources and the advantage of zero carbon dioxide emissions. However, achieving efficient, stable, and economically viable hydrogen production in seawater still faces many challenges, with catalyst design and optimization being recognized as key issues.Firstly, NiFe-LDH was synthesized using a simple one-pot solvothermal method. Subsequently, phosphorization, sulfurization, and sulfur-phosphorus co-doping were conducted to obtain samples namely NiFe-P, NiFe-S and NiFe-SP, respectively. Various electrochemical tests, including hydrogen evolution reaction (HER), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were firstly performed in simulated seawater to evaluate the electrochemical performance of the synthesized catalysts. The overall seawater splitting reaction was conducted with the same catalysts for both anode and cathode sides.After comparing the electrochemical activity of four different catalysts, it was found that NiFe-SP performs superior HER activity in alkaline simulated seawater. NiFe-SP required merely -0.143 V to deliver 100 mA cm-2 current density, which was 95 mV lower than NiFe-LDH to achieve the same current density. In EIS tests, NiFe-SP exhibited a smaller charge transfer resistance than NiFe-LDH, and NiFe-SP had the largest double-layer capacitance (Cdl) value in ECSA measurements, indicating that NiFe-SP possessed and lowest reaction resistance and the maximum electrochemically active surface area.X-ray Diffraction (XRD) and Raman spectroscopy analyses indicate that the catalyst, after sulfur-phosphorus doping, does not exhibit a pure-phase LDH structure but transforms into a heterogeneous structure of Ni3S2 and FeS2. Scanning Electron Microscopy (SEM) observations suggest that sulfur-phosphorus co-doping causes the original spherical structure of NiFe-LDH to aggregate, with the appearance of some lamellar structures on the surface. Energy Dispersive Spectroscopy (EDS) also confirms the successful doping of sulfur and phosphorus elements into NiFe-LDH, with uniform distribution on the material's surface.Finally, the catalyst underwent a 2000-hours continuous stability test at a constant current of 100 mA cm-² in real seawater. The results indicate that the potential of NiFe-SP increased by only 5%, demonstrating that the doping of sulfur and phosphorus not only reduces the catalytic overpotential but also significantly sustains potential retention. This suggests that the metal composite structure obtained after sulfur-phosphorus co-doping is well-formed and stable. The systematic electrochemical tests and stability evaluation in this study highlights the potential of sulfur-phosphorus co-doped metal composite NiFe-SP as an efficient and stable catalyst for real seawater electrolysis. This not only contributes to a deeper understanding of the fundamental principles governing catalyst behavior but also opens new possibilities for the practical application of hydrogen production technology. Figure 1

Verbena officinalis (VO) leaf extract as an anti-corrosion inhibitor for carbon steel in acidic environment

In the present work, Verbena Officinalis (VO) leaf extract was used as potential corrosion inhibitor for the corrosion of carbon steel (CS) in 0.5 M H2SO4 medium. Further, the corrosion inhibiting nature of VO leaf extract towards the CS was evaluated using mass loss (ML), potentiodynamic polarization (PDP), electrical impedance spectroscopy (EIS) and surface morphological analyses using atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS) techniques. Calculation of activation energy Ea∗\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\left( {{\ ext{E}}_{{\ ext{a}}}^{*} } \\right)$$\\end{document} using Arrhenius equation shows the increase in activation energy when adding the VO leaf extract in 0.5 M H2SO4 medium and the maximum activation energy (Ea∗\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{E}}_{{\ ext{a}}}^{*}$$\\end{document} = 49.9 kJ mol−1) was observed for 1000 mg L−1 VO leaf extract in acid medium. The negative free energy values suggested the spontaneous and the stability of the adsorbed layer of VO leaf extract on the CS surface. Using EIS measurements, high percent inhibitory effectiveness of 91.1% for 1000 ppm solutions was achieved. With an increase in VO leaf extract dose, the double layer capacitance (Cdl) values fall while the values of charge transfer (Rct) increase. This showed that a protective layer of VO leaf extract on CS surface was formed. The polarization curves showed that the VO leaf extract acts as a mixed-type inhibitor. It is discovered that the adsorption of VO leaf extract molecules adhering to the CS surface followed the Langmuir isotherm. The anti-corrosion action of VO leaf extract is fully demonstrated by some surface techniques.

Synergistic electrocatalytic activity unveiled: Cu–Mo bimetal sulfo-selenide nanocomposite for hydrogen evolution reaction

Developing an affordable and abundant electrocatalyst for generating green hydrogen is crucial for achieving sustainable energy with zero carbon emissions. In this context, nanostructured transition metal chalcogenides were seen as ideal cathode materials for water splitting due to their tuneable structure, large surface area, strong conductivity, and widespread availability. Herein, we have developed Cu–Mo Bimetal Sulfo-Selenide Nanocomposite (CuMoSSe) by incorporating Cu into the MoSSe system through a single-step hydrothermal method and explored it as a catalyst for electrochemical hydrogen evolution. The Cu0.25Mo0.75SSe, consisting of a Cu2Se/MoSSe composite structure, exhibited excellent electrochemical HER activity with an overpotential of 290 mV vs. RHE at 10 mA/cm2 compared to its various compositions and pristine counterparts, with remarkable stability for more than 1500 cycles and 12 h in an acidic medium. The enhanced electrochemical activity with smaller charge-transfer resistance (47.8 Ω) and larger double-layer capacitance (14.74 mF/cm2) values with a low Tafel slope of 79.1 mV/dec can be attributed to the effective kinetics and enhanced electrical conductivity of the composite due to the hybrid structure which is backed by the decrease in Gibbs free energy value calculated through theoretical studies. These discoveries open the door to creating new electrocatalysts using combinations of MoSSe and Cu or other metals. This approach aims to design electrode materials that are not only low cost but also mechanically strong and electrically conductive for the process of electrocatalytic water splitting.

Inhibition of corrosion of mild steel in simulated oil well waterby aqueous extract of Hibiscus rosa-sinensis flower

controlling the corrosion of mild steel in simulated oil well water (SOWW). Weight loss method reveals that 10 % v/v of the extract offers 82 % inhibition efficiency (IE) to mild steel (MS) immersed SOWW. The mechanistic aspects of corrosion inhibitive effect have been investigated by polarization study and AC impedance spectra. Polarization study reveals that the mixed type of inhibitor in the presence of inhibitor system. The corrosion inhibition effect is confirmed by the increase in the linear polarization resistance value and decrease in the corrosion current value. The protective layer is formed on the metal surface is confirmed by the AC impedance spectra. This is confirmed by the fact that there is increase in charge transfer resistance value and decrease in the double layer capacitance value. The adsorption of inhibitor molecule obey Langmuir adsorption isotherm. The protective coating is characterized by FTIR spectroscopy. It confirms that the inhibitor has coordinated with ferrous ion the metal surface through the active principle component of β-sitosterol, quercetin and kaempferol-3-xylosylglucoside. The surface morphology has been investigated by scanning electron microscopy (SEM). Hence, aqueous extract of Hibiscus rosa-sinensis flower with simulated oil well water good corrosive inhibitive effect on pipeline made of mild steel.

Electrochemical activities of Ni-Ti alloy in artificial blood plasma with Trigonella foenum graecum seeds

An investigation of the electrochemical behaviour of Ni-Ti alloy when exposed to artificial blood plasma (ABP) in the presence of 0.1 and 0.5 ppm of Trigonella foenum graecum (TFG) seeds for 1, 10, 20, and 30 days. Studies on AC impedance and polarisation have shown that a protective coating forms on the metal surface while inhibiting corrosion. The protective film has formed on the Ni-Ti implant alloy surface, the linear polarization resistance increased (LPR), and the corrosion current value (Icorr) decreased. The charge transfer resistant value (Rct) and impedance value increase and the double-layer capacitance value decrease.The protective layers morphology and the elemental composition were analyzed by SEM/EDAX. The property of the protective film on the Ni-Ti alloy has been examined by atomic force microscope. The X-ray diffraction analysis has confirmed the nature of the apatite. The corrosion inhibition efficiency of Ni-Ti alloy in ABP in the presence of TFG seeds at various concentrations for different times was improved and protected.

Corrosion inhibition by fruit extracts -Inhibition of corrosion of mild steel in simulated concrete pore solution prepared in sea water by an aqueous extract of apple juice- A Case study

The inhibition efficiency of an aqueous extract of apple juice in controlling corrosion of mild steel immersed in simulated concrete pore solution (SCPS) prepared in sea water, has been evaluated by weight loss method. Langmuir adsorption isotherm has been investigated. The mechanistic aspect of corrosion inhibition has been investigated by Electrochemical impedance spectra (AC impedance spectra). The protective film has been analysed by Fluorescence spectroscopy, FTIR spectroscopy and AFM. The SCPS system offers 60% inhibition efficiency to mild steel immersed in sea water. In presence of apple juice extract the inhibition efficiency increases as the concentration of the extract increases. When 10 ml of extract is added, 85% inhibition efficiency is obtained. Electrochemical impedance spectra (AC impedance spectra) reveal that a protective film is formed on the metal surface. In the presence of inhibitor system, charge transfer resistance value increases, impedance value increases, phase angle value increases whereas double layer capacitance value decreases as expected. The FTIR spectral study reveals that the protective film consists of complexes consisting of iron-active principles of the apple juice extract. AFM study reveals that when the inhibition efficiency increases the roughness of the surface decreases or in other words the smoothness of the system increases.

Dielectrophoretic and electrochemical impedance mapping of metastatic potential in MDA-MB-231 breast cancer cells using inkjet-printed castellated microarray.

The spread of metastatic cancer cells poses a significant challenge in cancer treatment, making innovative approaches for early detection and diagnosis essential. Dielectrophoretic impedance spectroscopy (DEPIS), a powerful tool for cell analysis, combines dielectrophoresis (DEP) and impedance spectroscopy (IS) to separate, sort, cells and analyze their dielectric properties. In this study, we developed and built out-of-plane inkjet-printed castellated arrays to map the dielectric properties of MDA-MB-231 breast cancer cell subtypes across their metastatic potential. This was realized via modulating the expression of connexin 43 (Cx43), a marker associated with poor breast cancer prognosis and increased metastasis. We employed DEP-based trapping, followed by EIS measurements on bulk cell population, for rapid capture and differentiation of the cancer cells according to their metastatic state. Our results revealed a significant correlation between the various MDA-MB-231 metastatic subtypes and their respective dielectrophoretic and dielectric properties. Notably, cells with the highest metastatic potential exhibited the highest membrane capacitance 16.88 ± 3.24 mF m-2, followed by the less metastatic cell subtypes with membrane capacitances below 14.3 ± 2.54 mF m-2. In addition, highly metastatic cells exhibited lower crossover frequency (25 ± 1 kHz) compared to the less metastatic subtypes (≥27 ± 1 kHz), an important characteristic for cell sorting. Finally, EIS measurements showed distinct double layer capacitance (CDL) values at 1 kHz between the metastatic subgroups, confirming unique dielectric and dielectrophoretic properties correlated with the metastatic state of the cell. Our findings underscore the potential of DEPIS as a non-invasive and rapid analytical tool, offering insights into cancer biology and facilitating the development of personalized therapeutic interventions tailored to distinct metastatic stages.

Layered MOF supported on 2D delaminated MXene (Mo2Ti2C3) nanosheets boosted water splitting.

Metal organic frameworks (MOFs) have a porous structure, high surface area, and high charge transfer, and they have been regarded as model electrocatalysts. Optimization of the electrocatalytic activity of MOFs is challenging, and an effective strategy for this optimization is the construction of a well-defined interfacial bond bridge. In this work, an in situ approach of composite synthesis is reported for MOF (CoNiNH2BDC) with MXenes (Mo2Ti2C3), as the electrocatalytic properties of MOF can be greatly enhanced with the incorporation of the conductive material MXene. The prepared composite material was characterized thoroughly using XRD, XPS, FESEM, EDX, TEM, and BET. The synergistic effect of both components of this composite material resulted in enhanced conductivity and the number of active sites, which led to enhanced electrocatalytic performance. The CoNiNH2BDC MOF with different ratios of Mo2Ti2C3 MXene were synthesized, and the resulting materials were evaluated for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) activities. It was observed that the MOFMX3 attained a 10 mA cm-2 current density at 1.44 V for OER and -0.037 V for HER (vs. RHE), and lower values of Tafel slopes of 44.8 mV dec-1 for OER and 45 mV dec-1 for HER in 0.1 M KOH were achieved. The higher double layer capacitance (C dl) values lead to high electrochemical surface area (ECSA) values. Lower Tafel slope values for MOFMX3 show that the presence of MXene nanosheets in the hybrid provides support to the layered and porous configuration of MOF, and the chances of the interaction of electrolyte to the catalytically active sites are significantly enhanced. This work highlights the idea of growing bimetallic MOFs on Mo2Ti2C3 MXene using an interdiffusion reaction strategy and opens up an avenue for designing highly electrocatalytic systems.

Anti-corrosive and self-healing properties of epoxy coatings loaded with montmorillonite modified with zinc-based ionic liquid

In this work, the outstanding corrosion resistance of coated steel and self-healing ability of epoxy coatings loaded with 1 % of sodium montmorillonite (MMT-Na+) clay modified with bis-(1-butyl-3-methylimidazolium) zinc tetrachloride (bmim2[ZnCl4]) was successfully demonstrated. The corrosion protection properties and self-healing ability of artificially scratched ER coatings containing 1 % of MMT-bmim2[ZnCl4] were compared with those loaded with MMT-Na+, MMT-ZnCl2 and the MMT modified with the ionic liquid 1-butyl-3-methylimidazolium chloride (bmimCl), using electrochemical impedance spectroscopy (EIS) under saline medium. The presence of 1 % clay modified with ZnCl2 and bmim2[ZnCl4] promoted outstanding anti-corrosion protection to the scratched ER coatings. The last one exhibited the best anti-corrosive response, whose |Z|f=0.01Hz value corresponded to 2.9 × 106 Ω·cm2 after 24 h immersion and increased by around two orders of magnitude after 360 h immersion in saline solution. Furthermore, the charge transfer resistance (Rct) increased after 360 h immersion followed by significant decrease in double-layer capacitance values (Cdl) at the electrolyte/metal interface. The self-healing ability was also confirmed by SEM/EDX (due to the presence of Zn in the scratched region) and by visual observation of the scratched region after immersion in the saline solution for 360 h.

Effect of OH position on adsorption behavior of Schiff-base derivatives in corrosion inhibition of carbon steel in 1 M HCl

In this work, we have synthesized two new Schiff-bases from 2,2-dimethylpropane-1,3-diamine and n-hydroxy-n-methoxybenzaldehyde. The synthesized Schiff-bases were characterized by 1H NMR, 13C NMR. The anti-corrosive property of the compounds were investigated using weight loss, polarization and EIS techniques against 1 M HCl solution. For additional support for this work, DFT studies also carried out for Schiff-bases. The surface morphology was examined by AFM and SEM to determine this inhibition mechanism. Schiff-base derivatives were found to successfully suppress steel corrosion. EIS studies showed that charge transfer resistance occurs because of the presence of an inhibitor. Moreover, increasing Schiff-bases concentration decreased the double-layer capacitance (Cdl) value because less charged species were attracted to the metal surface. Polarization measurements clearly showed that the inhibitors suppressed both anodic and cathodic reactions. In conclusion, this study demonstrates that these compounds inhibit corrosion via chemisorption of organic compounds. By studying the effects of hydroxyl groups in ortho-, para- positions, the best one as inhibitor was found to be ortho position of OH in Schiff base (i.e., 6-SH).

One-step electrodeposition of NiS heterostructures on nickel foam electrodes for hydrogen evolution reaction: on the impact of thiourea content

Herein, we report on the one-step growth of nickel sulfide (NiS) heterostructures on nickel foam (NF) substrate via a facile electrodeposition method, employing Ni(NO3)2.6H2O and CH4N2S as Ni and S precursors, respectively. For the first time, a systematic study was carried out on the impact of the Ni/S molar ratio on the electrochemical performance of as-prepared electrodes for water splitting. The optimum performance was obtained for a Ni:S ratio equal to 2:1, whereas lower or higher ratios resulted in much inferior performance. The NiS@NF electrode with a Ni:S ratio of 2:1 exhibited the lowest overpotentials |η10| = 136 mV, |η100| = 209 mV, extremely low Tafel slope (60 mV dec-1), and very high double layer capacitance value (2.78 mF cm-2). Field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), and X-ray photoelectron spectroscopy (XPS) revealed the formation of coral-like nanoarchitecture, resulting in enhanced HER activity.

A Physical Impedance Model of Lithium Intercalation into Graphite Electrodes for a Coin‐Cell Assembly

AbstractGraphite electrodes are widely used in commercial metal‐ion batteries as anodes. Electrochemical impedance spectroscopy serves as one of the primary non‐destructive techniques to obtain key information about various batteries during their operation. However, interpretation of the impedance response of graphite electrodes in contact with common organic electrolytes can be complicated. It is especially challenging, particularly when utilizing the 2‐electrode configuration that is common in battery research. In this work, we elaborate on a physical impedance model capable of accurately describing the impedance spectra of a graphite|electrolyte|metallic Li system in a coin‐cell assembly during two initial charge/discharge cycles. We analyze the dependencies of the model parameters for graphite and metallic lithium as a function of the state of charge to verify the model. Additionally, we suggest that the double layer capacitance values obtained during specific intercalation stages could help to determine if the area‐normalized values align with the expected range. The data and the procedure necessary for calibration are provided.

Boron-doped {113}, {115} and {118}-oriented single-crystal diamond electrodes: Effect of surface pre-treatment

In this study, the effect of vicinal crystal orientation ({113}, {115}, and {118}), boron doping level, and surface termination induced by various pre-treatments on electrical and electrochemical properties of single crystal boron-doped diamond (SC-BDD) electrodes was carefully investigated. van de Pauw measurements confirmed Hall concentration to increase with increasing vicinal angle, {118} < {115} < {113}. As-deposited H-terminated surfaces were converted to predominantly O-terminated surfaces (confirmed by X-ray photoelectron spectroscopy) using hot acid, ozone and anodic pre-treatments, or by spontaneous oxidation in air. This conversion was recognized by inhibited heterogeneous electron transfer kinetics of inner-sphere redox markers ([Fe(CN)6]3−/4− and dopamine), by an increase in double layer capacitance and charge transfer resistance values. The most pronounced surface oxidation was recognized for electrodes with the lowest boron content as a result of blocked boron atoms by oxygen functionalities and loss of superficial hydrogen on the surface. Reverse conversion from oxidized to H-terminated surfaces using cathodic pre-treatment led mainly to restoration of electrochemical parameters. Moreover, spontaneous oxidation of electrode surfaces in ambient atmosphere was confirmed, with the fastest being within the first five days. The results show the key role of boron content, and hence the crystal orientation and superficial hydrogen in affecting conductivity and performance of SC-BDD electrodes, which is demonstrated by changes in heterogenous electron transfer kinetics of surface sensitive redox systems.

Exploration of Bifunctionality in Mn, Co Codoped CuO Nanoflakes for Overall Water Splitting

Herein, bimetal (Mn, Co) codoping on a CuO host is aimed at enhancing oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) activity. Codoping of Mn and Co on CuO to enhance bifunctional action in electrochemical water splitting has not yet been investigated to the best of our knowledge. Literatures are focused on unary Mn-doped CuO or Co-doped CuO nanostructures. Mn, Co codoped CuO through an easy chemical coprecipitation method has been successfully attempted and is more beneficial which is the novelty of the present work. Defect-enriched ample active sites (Mn2+/Mn3+ and Co2+/Co3+) along with Cu2+ in the host CuO achieved high current density (100 mA/cm2) in OER and HER with low overpotential such as 468 mV and 271 mV, respectively. Faster charge transfer and diffusion ability was stimulated by the bimetal codoping CuO. Reasonable Tafel plot values (OER: 199 mV/dec, and HER: 21 mV/dec) with improved water-splitting reaction kinetics were achieved for the Mn, Co codoped CuO nanoflakes. The double-layer capacitance ( C dl ) value of 27.5 mF/cm2 for Mn, Co codoped CuO nanoflakes was achieved. Similarly, the increasing order of an electrochemically active surface area (EASA) was exhibited by the consequent addition of bimetal doping on CuO, denoted as Mn , Co / CuO &gt; Co / CuO &gt; Mn / CuO &gt; CuO . The evidence shows that the codoping strategy could facilitate rapid reaction kinetics to develop overall water splitting. The charge transfer resistances ( R ct ) of 3.6 Ω and 1.2 Ω for the Mn, Co codoped CuO nanostructure corresponding to the OER and HER, respectively, were reported. The long-term stability over 16 h with negligible loss was reported for both the OER and the HER performance. Thus, this work contributes to better insight and analysis of the successful codoping of bimetal elements in earth-abundant electrocatalysts to enhance and make practical the electrocatalytic water-splitting activity.

Co₃O₄/g-C₃N₄ nanocomposite for enriched electrochemical water splitting

Designing an ideal bi-functional electrocatalyst for the overall water splitting plays significant function in alternative energy construction. Based on the previous literatures, the Co3O4/g-C3N4 nanocomposite has been investigated as the bi-functional electrocatalyst. In the present study, the facile hydrothermal route was approached to synthesize the Co3O4/g-C3N4 nanocomposite to enhance the electrocatalytic activity towards oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Further, Co3O4/g-C3N4 electrochemical analysis was undergone in an aqueous alkaline solution of 1 M potassium hydroxide for both OER and HER. High electrocatalytic nature of prepared Co3O4/g-C3N4 nanocomposite delivered the low 170 mV overpotential value and 151 mV at 20 mA/cm2 with Tafel values 188 mV/dec and 176 mV/dec for OER and HER. Also electrochemical surface area (ECSA) of prepared Co3O4/g-C3N4 nanocomposite was estimated from double layer capacitance (Cdl) values, and calculated ECSA values are 0.027 cm2 and 0.097 cm2 for OER and HER respectively. The resultant Co3O4/g-C3N4 nanocomposite reached the low charge transfer resistance value of 15.9 Ω for OER and 22.7 Ω for HER which could acts as strong parameter to improve conductivity of the prepared electrode for both half reactions. Along with that, stability of Co3O4/g-C3N4 nanocomposite exhibits the outstanding performance at the current density of 10 mA/cm2 with only minimum amount of loss even after 16 h for both OER and HER. Hence, the synthesized Co3O4/g-C3N4 nanocomposite was act as an optimistic choice of the bi-functional electro catalyst for sustainable energy production.

Corrosion mitigation on orthodontic wire made of SS 18/8 alloy using esomeprazole tablet (Esiloc-40 mg) in artificial saliva

The corrosion inhibition of orthodontic wire made of SS 18/8 alloy in artificial saliva, with and without the presence of tablet esomeprazole − 40 mg has been investigated by electrochemical analysis. Polarisation study indicates that in the presence of the mentioned tablet, polarisation resistance (Rp) value increases and corrosion current (Icorr) decreases. That is, the corrosion resistance of SS 18/8 alloy in artificial saliva increases. AC impedance spectroscopy reveals that charge transfer resistance value (Rct) value increases and double layer capacitance value (Cdl) decreases. The open circuit potential (OCP) values for the inhibited system are more negative than that of the uninhibited blank system. The vibration peaks obtained from the FTIR spectra indicates the presence of functional group in esomeprazole pill and these characteristic peaks are slightly shifted in the analyzed scratched film from the surface of the orthodontic wire after immersion. AFM micrograph image of the polished specimen sample immersed in artificial saliva (AS) with esomeprazole tablet solution shows lesser degree of surface deterioration than those for SS 18/8 specimen immersed only in artificial saliva. From the present work, it is reported that people clipped with orthodontic wire made of SS 18/8 alloy need not worry about orthodontic corrosion for taking esomeprazole tablet for the treatment of gastro esophageal reflux disease and other medicinal purpose.

Electrochemical and surface study of an antibiotic drug as sustainable corrosion inhibitor on mild steel in 0.5 M H2SO4

Corrosive degradation of mild steel using the antibiotic ethambutol hydrochloride drug as a sustainableinhibitor in 0.5 M sulphuric acid was studied and found as an efficient inhibitor. The inhibitive action showed an increase with an upsurge in the drug concentration, but with escalating temperature, inhibition efficiency declined. The drug showed a best of 92.78% inhibition efficiency at 1000 ppm and 313 K. The thermodynamic, kinetic and adsorption parameters were evaluated and established the physisorption of the drug over the metal surface following Langmuir adsorption isotherm. The EIS analysis confirmed the adsorption of inhibitor on the metal surface by showing the lowering in the value of double layer capacitance, Cdl; improvement in charge transfer resistance, Rct as the surface modulus raised. The mixed type of inhibition mechanism was confirmed by a Potentiodynamic polarization experiment. Surface morphology through Atomic Force Microscopy (AFM) validated the less deteriorated metal surface exposed to corrosive medium in presence of the drug.

Electrochemical and theoretical investigations of favipiravir drug performance as ecologically benign corrosion inhibitor for aluminum alloy in acid solution

Aluminum–silicon alloys have become a preferred option in the automotive and aerospace industries thanks to their fault-tolerant process ability and reasonable static characteristics at relatively affordable costs. This study aimed to investigate the use of favipiravir (FAV) drug as a biocompatible and eco-friendly inhibitor to protect aluminum alloy (AlSi) surface in an aggressive acid environment (1.0 M HCl). The electrochemical measurements declare that FAV is categorized as an inhibitor of mixed type with a cathodic effect. At 100 ppm, FAV had the highest inhibitory efficiency (96.45%). FAV is associated with lower double-layer capacitance values and more excellent charge-transfer resistance. These results show that AlSi corrosion in 1.0 M HCl is reduced in the presence of FAV. The Langmuir model is well-suited to the FAV adsorption behavior (R2 ≈ 1). Chemisorption is the primary adsorption in this environment. The theoretical calculation studies corrosion inhibitors' molecular structure and behavior. Different quantum chemical properties of the FAV have been calculated, including energy difference (ΔE), softness, global hardness, and energy of back-donation depending on the highest occupied and lowest unoccupied molecular orbitals. In addition, Mulliken and Fukui’s population analysis and the Molecular Electrostatic Potential map represent the electron distribution and the molecule’s active centers. Experimental findings and quantum chemical computations matched, and FAV is recommended as a green corrosion inhibitor.