Chronoamperometry Methods Research Articles

(Digital Presentation) Carbon Aerogel Platinum-Praseodymium Oxide Nanocatalyst for Methanol Oxidation in 0.5 M Sulfuric Acid

Electrooxidation of methanol is an essential topic in developing direct methanol fuel cells, and numerous catalyst materials have been studied for this application. 1–3 Among other materials, the platinum-based composite catalysts containing rare earth metal oxides on various support materials have shown promising properties for methanol oxidation and implementation for direct methanol fuel cells.1–3 In this study, platinum-praseodymium oxide nanocatalyst on carbon aerogel support for methanol oxidation was synthesized. The material was electrochemically characterized using rotating disk electrode, cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy methods. X-ray diffraction, specific surface area measurements, thermogravimetric analysis, and high-resolution scanning electron microscopy with energy dispersive X-ray analysis were used to determine the physical properties of the material.The catalyst was synthesized by depositing platinum4 on a pyrolyzed organic aerogel doped with Pr(NO3)3 5,6. Synthesized nanocatalyst material contained 21 wt% of Pt and 20 wt% of PrOx. This material has micro-mesoporous structure with surface area of 230 m2 g−1, micropore area of 70 m2 g−1, total pore volume of 0.62 cm3 g−1 and micropore volume of 0.032 cm3 g−1. Pt and PrOx particles were uniformly dispersed on the supporting carbon aerogel-derived material.Electrochemical measurements showed that the studied material has an electrochemically active surface area of 54 mPt 2 gPt −1, which is noticeably higher than that for commercial Pt-Vulcan catalyst (17 mPt 2 gPt −1) and comparable with similar composite catalyst materials containing rare earth metal oxides (from 45 mPt 2 gPt −1 up to 61 mPt 2 gPt −1).3 For methanol electrooxidation the synthesized material showed high current density peaks in both anodic (310 A gPt −1) and cathodic (240 A gPt −1) potential sweeps. These current densities are higher than measured for commercial Pt-Vulcan catalyst (for the peaks in both anodic (178 A gPt −1) and cathodic (167 A gPt −1) potential sweeps). Furthermore, the synthesized material demonstrated the ability of preserving higher catalytic activity (0.33 A gPt −1) than the commercial Pt-Vulcan catalyst (0.07 A gPt −1) after working on a fixed potential of ‒0.2 V vs RHE for an extended period of time (30 min). While these results outstand the catalytic activity of some similar catalyst materials containing praseodymium,1,7,8 higher current densities on both cathodic and anodic potential sweep have been measured with Pt-PrOx catalyst deposited on carbon black Vulcan XC-72R.3 These characteristics show good suitability of the developed nanocatalyst for methanol oxidation in direct methanol fuel cells.This study shows the potential of nanocatalysts containing rare earth metal oxides and catalyst on the carbon aerogel support for methanol electrooxidation. These materials could be further investigated for the electrooxidation for ethanol or other organic fuels. Acknowlegements This work was supported by the EU through the European Regional Development Fund TK141 “Advanced materials and high-technology devices for energy recuperation systems” (2014-2020.4.01.15-0011), the Estonian Energy Technology Program: SLOKT10209T “Nanomaterials – research and applications (NAMUR)” project 3.2.0304.12-0397and Personal Research Grant PRG676. References Z. Tang and G. Lu, J. Power Sources, 162, 1067–1072 (2006).P. Valk et al., J. Electrochem. Soc., 165, F315–F323 (2018).P. Valk et al., J. Electrochem. Soc., 166, F1062 (2019).C. Galeano et al., J. Am. Chem. Soc., 134, 20457–20465 (2012).K. Kreek, M. Kulp, M. Uibu, A. Mere, and M. Koel, Oil Shale, 31, 185–194 (2014).K. Kreek et al., J. Non-Cryst. Solids, 404, 43–48 (2014).A. O. Neto et al., J. Alloys Compd., 476, 288–291 (2009).L. Chen, J. Hu, and J. S. Foord, Phys. Status Solidi A, 209, 1792–1796 (2012).

(Digital Presentation) Water-Soluble Binders That Enhance Electrochemical Sodium-Ion Storage Properties of NaTi2(PO4)3 Nanoparticle Anodes

Sodium ion batteries (SIBs) have been considered as one of the most promising alternative to conventional lithium-ion batteries (LIBs) for next generation energy storage systems.1 , 2 In terms of anodes, commercial graphite only delivers a sodium-ion storage capacity of 31 mAh g−1.3 The polyanionic-type NaTi2(PO4)3 material is an attractive anode because of the crystal structure of a Na-super-ionic conductor (NASICON), high theoretical capacity, safety characterization and ‘zero-stress’ framework upon sodiation/desodiation.4 , 5 The primary role played by the binder is to link different types of small particles together and to ensure the active material adheres to the current collector, which has an important contribution to the electrical and mechanical behaviour of the electrode.6 , 7 Poly(vinylidene fluoride) (PVDF) is a common organic binder using N-methyl-2-pyrrolidone (NMP) as solvents. Sodium carboxymethyl cellulose (CMC) has been considered as an effective and green water-soluble binders. Styrene butadiene rubber (SBR) typically serves as an elastomer in water-soluble CMC binders and further increases binding force, adhesion, heat resistance, and flexibility of an electrode. The role of different binders on the structural/chemical stability of NaTi2(PO4)3 anode in SIBs has rarely been studied.Here, we synthesized NaTi2(PO4)3 nanoparticles using the hydrothermal method and explore the effects and influence of PVDF, CMC and CMC-SBR binders on the sodium-ion storage performance of NaTi2(PO4)3 anodes. Compared to traditional organic PVDF binder, water-soluble binders improved the cycling stability by increasing adhesion, flexibility, and mechanical properties between the active materials, conductive addictive and current collector. Notably, water-soluble binders show an important effect on the sodium storage mechanism of NaTi2(PO4)3 nanoparticles. The addition of SBR in the water-soluble binders further enhances the active materials areal specific capacity because of its better adhesion ability, reducing the overall quantity of binder polymer required for the electrode. This novel exploration of the effective combination of water-soluble CMC and SBR binders for NaTi2(PO4)3 anodes in SIBs not only provides an opportunity to enhance their electrochemical sodium storage properties, but may enables their practical application in high areal energy density sodium ion batteries in the future. References (1) Nayak, P. K.; Yang, L.; Brehm, W.; Adelhelm, P.: From Lithium-Ion to Sodium-Ion Batteries: Advantages, Challenges, and Surprises. Angew. Chem. Int. Ed. 2018, 57, 102-120.(2) Kim, S.-W.; Seo, D.-H.; Ma, X.; Ceder, G.; Kang, K.: Electrode Materials for Rechargeable Sodium-Ion Batteries: Potential Alternatives to Current Lithium-Ion Batteries. Adv. Energy Mater. 2012, 2, 710-721.(3) Doeff, M. M.; Ma, Y.; Visco, S. J.; De Jonghe, L. C.: Electrochemical insertion of sodium into carbon. J. Electrochem. Soc. 1993, 140, L169-L170.(4) Delmas, C.; Cherkaoui, F.; Nadiri, A.; Hagenmuller, P.: A nasicon-type phase as intercalation electrode: NaTi2(PO4)3. Mater. Res. Bull. 1987, 22, 631-639.(5) Chen, S.; Wu, C.; Shen, L.; Zhu, C.; Huang, Y.; Xi, K.; Maier, J.; Yu, Y.: Challenges and Perspectives for NASICON-Type Electrode Materials for Advanced Sodium-Ion Batteries. Adv. Mater. 2017, 29, 1700431.(6) Chen, H.; Ling, M.; Hencz, L.; Ling, H. Y.; Li, G.; Lin, Z.; Liu, G.; Zhang, S.: Exploring Chemical, Mechanical, and Electrical Functionalities of Binders for Advanced Energy-Storage Devices. Chem. Rev. 2018, 118, 8936-8982.(7) Bommier, C.; Ji, X.: Electrolytes, SEI Formation, and Binders: A Review of Nonelectrode Factors for Sodium-Ion Battery Anodes. Small 2018, 14, 1703576. Figure 1 (a) SEM image and (b) HRTEM image of NaTi2(PO4)3 nanoparticles with quasi-cubic architecture and hollow structure. (c) XRD analysis of the synthesized nanoparticles. (d) Specific capacity versus rate data using chronoamperometry (CA) method for NaTi2(PO4)3 nanoparticles anode of different binders. (Inset) Corresponding digital photos for NTP electrodes with different binders. (e) The first cycle in the cyclic voltammetric curve at a scan rate of 0.1 mV s-1 for NaTi2(PO4)3 nanoparticles anode. (f) Galvanostatic discharging and charging cycling stability at 0.2 C (1C = 133 mA g-1) for the NaTi2(PO4)3 nanoparticle anode with different binders. Figure 1

Binary spindle-like cobalt–iron layered-double hydroxide as an efficient electrocatalyst for oxygen evaluation reaction

In this research, inexpensive transition metals are used for electrocatalytic oxygen evolution reactions. Nickel foam was modified as a substrate using spindle-like Co–Fe LDH. XRD, FE-SEM, EDS, and elemental mapping techniques are used for characterization. Based on LSV results, overpotentials of 280 and 355 mV were obtained at 10 and 100 mA cm−2, respectively. To evaluate the stability of electrocatalyst, cyclic voltammetry, chronoamperometry (at constant potentials of 1.55 and 1.65 V vs. RHE), and chronopotentiometry (at applied current densities of 10 and 100 mA cm−2) methods are used. All stability tests were performed consecutively using one electrode. Current density increased by 0.05% after performing 500 CV cycles. The catalytic performance was enhanced during the chronoamperometry analysis. However, the potential decreased slightly by less than 0.44% after 7200 s at 100 mA cm−2 in chronopotentiometry analysis. The high durability and current density ensure the efficient performance of the as-prepared electrocatalyst in water splitting process.

Facile synthesis of Cu@Cu2O aerogel for an effective electrochemical hydrogen peroxide sensor

Herein, a facile one-step reduction method was used to synthesize Cu@Cu 2 O aerogel to fabricate an electrochemical sensor for detection of hydrogen peroxide. Advanced techniques including X-ray powder diffractions (XRD), transmission electron micrographs (TEMs), field-emission scanning electron microscopy (FESEM) were utilized to characterize the structure of Cu@Cu 2 O aerogel. The results showed that the Cu@Cu 2 O aerogel is composed of Cu and Cu 2 O nanoparticles with a three-dimensional porous structure. The chronoamperometry method was implemented to evaluate the electrochemical performance of Cu@Cu 2 O/GCE (GCE=glassy carbon electrode) towards H 2 O 2 . Under optimal conditions, Cu@Cu 2 O/GCE showed a wide detection range (2∼860 μmol), a low detection limit (0.46 μM, S/ N = 3), a sensitivity of 1855.53 mA M − 1 cm −2 and a good selectivity. In addition, the electrochemical sensor based on Cu@Cu 2 O aerogel can be used for the determination of hydrogen peroxide in watery samples. .

Sensitive determination of hydroxylamine by using modified electrode by La2O3–Co3O4 nanocomposite and ionic liquid

In the present work, an efficient, fast and sensitive method for the determination of hydroxylamine (HyA) has been developed based on carbon paste electrode (CPE) modified with La2O3/Co3O4 nanocomposite and ionic liquid (LaCo/IL/CPE). The developed method was assessed using cyclic voltammetry, chronoamperometry and differential pulse voltammetry (DPV) methods. The LaCo/IL/CPE sensor showed good response ability and good electrocatalytic activity for HyA. The results showed that, electrochemical oxidation signal of HyA at the surface of LaCo/IL/CPE was 4.8 times the signal at the surface of LaCo/CPE. Also, potential of peak (Ep) of HyA at the surface of LaCo/IL/CPE was 700 mV while at the bare CPE, HyA was not oxidized until the potential reached +1200 mV. The obtained results showed that the oxidation process of HyA at the LaCo/IL/CPE was controlled by diffusion and the average diffusion coefficient for HyA, 2.8 × 10−6 cm2/s was obtained. The experimental conditions such as pH of solution, scan rate and instrumental parameters for DPV were assessed and optimized for electrochemical determination of HyA. Under optimum conditions, a linear response for HyA in the concentration range 0.06–240.0 μM was found, with a detection limit of 3.0 nM. In the final, HyA in different water samples was detected by the standard addition procedure.

Dual-Mode electrochemical biosensors based on Chondroitin sulfate functionalized polypyrrole nanowires for ultrafast and ultratrace detection of acetamiprid pesticide

The inappropriate and excessive use of pesticides poses a great challenge to human health. It is necessary to analyze pesticide residues efficiently, economically and quickly to minimize the risk of public safety issues. Herein, a dual-mode biosensor was proposed for ultrafast and ultratrace detection of acetamiprid (ACE). The polypyrrole nanowires (PPyNWs) was prepared using the guidance of CS by electrochemical method, which showed large electroactive surface area, excellent conductivity and high stability. After immobilization of ACE aptamer onto CS/PPyNWs, the biosensor can be effortlessly prepared. The ACE concentration can be measured by both the signal decrease of the chronocoulometry (CC) method and the chronoamperometry (CA) method. The dual-mode biosensor exhibited ultrafast detection speeds of 0.5 s and 2 s across 9 and 6 orders of magnitude linear ranges through CC and CA, respectively. More importantly, the biosensor was successfully applied to detect ACE residues in soil samples, proving the feasibility of the dual-mode biosensor for ACE detection in complex samples.

An extremely sensitive carbon paste electrode modified with Prussian blue analogue (PbA @CPE) for the electrochemical determination of Tetramisole HCl anthelmintic drug as a food contaminant in beef cuts and infant formula milk powder

Tetramisole hydrochloride (TMS) - the drug of choice for ascariasis- is used as an anthelmintic. In this paper, both qualitative and quantitative determination of TMS in bulk, infant milk powder, and frozen cuts-up bovine meat samples were developed to provide consumersafety. In this paper, chemically modified carbon paste with Prussian blue analogue nanoparticles (PbA-NPs /CP) was developed for determination of TMS utilizing cylic voltammetry (CV), square wave voltammetry (SWV) and chronoamperometry methods. In this regard, Prussian blue analogue (PbA) was synthesized by the chemical co-precipitation route. XRD technique was used for crystal structure analysis indicating that the fabricated nanopowder belongs to a cubic structure with lattice constants a=b=c=10.176AThe grain size was estimated approximately equal 20 nm, and the dislocation density was 25×10-4nm-2. The molecular structure was analyzed using Raman spectroscopy, and the elements C, N, O, Co, Ni, Cr, Ir were recorded by EDX spectrum. SEM images showed the particles very fine in spherical shape. Transmittance and reflectance spectra have been measured through wavelength range from 200 nm to 900 nm.Energy gap (Eg) and refractive index (n) of the films were determined suggesting the strong optical absorption. Finally, this method was carried out at pH 4.0 within a linearity range (10.0 × 10−9–1.0 × 10−4) M and a minimum detection limit of 2.7 × 10−9M.

PANI-ZnO/Pt–Ru electrocatalyst for methanol oxidation: Synthesis, characterization, electrocatalytic performance and artificial neural network modeling

In methanol oxidation, fabrication of novel electrocatalysts consisted of a lower loading of precious metals like platinum and ruthenium as well as possessing great electrocatalytic performance is of interest. One approach is to use an appropriate substrate. In this study, Polyaniline-Zinc oxide (PANI-ZnO) nanocomposites were prepared by polymerization method. Then, PANI-ZnO/Pt–Ru electrocatalyst was fabricated using the synthesized nanocomposites as a platinum and ruthenium (Pt–Ru) substrate. Field Emission Scanning Electron Microscopy (FESEM) was applied to study the morphology of the samples, while X-ray diffraction (XRD) analysis and Fourier Transform Infrared Spectroscopy (FTIR) were used to evaluate their phase structure and chemical groups, respectively. Electrochemical behaviors of fabricated PANI-ZnO/Pt–Ru electrocatalyst in the oxidation of methanol were specified via linear sweep voltammetry (LSV), cyclic voltammetry (CV), and chronoamperometry (CA) methods. The current density of PANI-ZnO/Pt–Ru was 91.14 mA/cm2, which was about 15% greater than the current density of Pt/Ru. This reflects the high catalytic performance of the electrocatalyst in the presence of nanocomposites. The electrochemically active surface area of the PANI-ZnO/Pt–Ru and Pt–Ru electrocatalysts are 37.72 m2/g and 21.22 m2/g, respectively. This increase is due to the specific morphology in the structure of nanocomposites. In general, these findings exhibited that the presence of PANI-ZnO support could enhance the catalytic performance and stability of Pt–Ru electrocatalysts. Besides, artificial neural network (ANN) model was used to predict the rate-determining reaction in methanol oxidation at different electrodes and the results indicated the efficiency of the model for forecasting.

Improving water desalination performance of electrospun carbon nanofibers by supporting with binary metallic carbide nanoparticles

Capacitive deionization (CDI) technology is proposed as an environmentally friendly way to desalinate brackish water samples with outstanding efficiency. Since the nanomaterial composition is the controlling factor in the measured activity of fabricated CDI cells, much efforts are directed to explore highly effective nanocomposites with increased electrosorptive capacity and enhanced regeneration behavior during operation for longer periods. Here, the electrospinning process was devoted to synthesize mixed cobalt and titanium carbides nanoparticles onto carbon nanofibers [Co–TiC@CNFs] using cobalt acetate tetrahydrate (CoAc) and titanium (IV) isopropoxide (TIP) as precursor salts and polyvinylpyrrolidone (PVP) as a carbon source. Electrospun mats were then calcined at 950 °C for 6 h using a tube furnace with passing argon gas. This formed nanoporous material could provide numerous pathways for increased ions adsorption with extraordinary electrical conductivity. This could explain its enhanced electrochemical properties as evidenced by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy (EIS) methods. A specific capacitance value of 979.40 F g −1 was estimated for Co–TiC@CNFs as 7.42 times higher than that for bare CNFs. Furthermore, this nanohybrid material had a salt adsorption capacity of 33.10 mg g −1 in 1.0 M NaCl solution at 1.2 V that highly exceeded the obtained ones for TiC [2.20 mg g −1 ] and CNFs [8.20 mg g −1 ]. Accordingly, modifying carbon nanofibers with metallic carbides can create suitable nano-constituents for promising CDI cell output.

Green electrochemical method for the synthesis of nitro and azo derivatives based on mefenamic acid

Electrochemical study of mefenamic acid (MFA) was carried out with details in water/ethanol mixture by the various voltammetric techniques. The results showed that the oxidation of MFA is highly dependent on pH and follows the Eir mechanism. The EpA1-pH diagram plotted based on the differential pulse voltammograms shows two linear segments, 66 and 26 mV/pH slope. Also, the diffusion coefficient and the surface excess, Ӷ* of MFA in aqueous buffered solution, determined by using the single potential-step chronoamperometry and chronocoulometry methods. Electrochemical nitration of MFA in an aqueous solution and the presence of nitrite ion (1) were both investigated by the cyclic voltammetry and controlled-potential coulometry techniques. Our results indicate that the oxidized form of MFA participates in a Michael-type addition reaction with nitrite ion (1) to form the corresponding Nitromefenamic acids (MFA-4-NO2 and MFA-5-NO2). Also, in another part, a computational study based on the density functional theory (DFT/B3LYP) was performed for the prediction of the best possible pathway in the nucleophilic addition of nitrite ion (1). The electrochemical reduction of produced nitromefenamic acids was investigated using cyclic voltammetry and controlled-potential coulometry techniques. Eventually, two new azo derivatives have been generated via electroreduction of produced nitromefenamic acids and conduction of diazotization reaction, respectively. Both nitro and azo products are approved as paints.

Influence of applied potential on tin content in electrodeposition of Zn–Sn alloy coatings and its effect on corrosion protection

In the present work, the electrochemical deposition of Zn–Sn alloy at different applied potentials is studied. The deposits were prepared from a chloride bath on a stainless steel substrate (SS) using cyclic voltammetry, chronoamperometry and anodic linear stripping voltammetry methods. X-ray diffraction, scanning electron microscopy and energy dispersive were used to study the structural, morphological and chemical composition of the deposits. The corrosion behavior of the elaborated samples was studied by open circuit potential (OCP), Tafel plot and electrochemical impedance spectroscopy (EIS) in 3.5 wt-% NaCl solution. Results indicated that the Zn–Sn alloy coatings exhibit a synergistic property combining the barrier behavior afforded by Sn and strong passive behavior of Zn. Electrochemical measurements obtained by Tafel and EIS plots revealed that Zn–Sn alloy coatings obtained at more positive potential of −1.1 V present best corrosion resistance.

Nucleation and growth mechanism of cuprous oxide electrodeposited on ITO substrate

The electrodeposition mechanisms of cuprous oxide (Cu2O) from copper nitrate solutions on indium tin oxide (ITO) were investigated using the cyclic voltammetry and the chronoamperometry methods. Then the kinetics parameters, nucleation and growth mechanism were explored. The CV measurement showed that the electrodeposition of Cu2O takes place by cathodic reduction at potential −0.5 V versus saturated calomel electrode (SCE). Furthermore, the voltammograms at different scan rates revealed that the electrodeposition reaction of Cu2O is a quasi-reversible reaction controlled by the diffusion of copper ions. Moreover, the deposition mechanism of Cu2O on the ITO substrate determined by the Astley approach and confirmed by the Scharifker-Hills models follows an instantaneous three-dimensional (3D) nucleation controlled by diffusion with an average diffusion coefficient D of 0.549 10-6 cm2 s−1. The X-ray diffraction pattern of Cu2O film was indexed to cubic crystal structure. The scanning electron microscopy analysis indicated that the average size of the cuprous oxide particles is about 1.408 µm. The optical energy band gap (Eg) was calculated by Tauc’s plot for Cu2O is 2.16 eV. The theoretical analyses reveal that Cu2O has an energy band gap of 2.25 eV, which corresponds to experimental results.

Investigation of nucleation and growth mechanism of selenium electrodeposited on ITO substrate

The present paper reports an investigation of the electrodeposition mechanism of selenium (Se) thin films from an aqueous solution containing selenite ion (HSeO3−) (2 mM) and nitric acid on indium tin oxide (ITO) substrate, with pH 3.2 at room temperature, by using the cyclic voltammetry (CV) and chronoamperometry (CA) methods. The (CV) showed that the electrodeposition reaction is a quasi-reversible controlled by selenite ions diffusion. The (CA) indicated that the selenium particles are electrodeposited following the instantaneous three-dimensional (3D) nucleation model with a diffusion-controlled process, and the average diffusion coefficient (D) of selenite ions was determined to be 2.860 10−6 cm2 s−1. The X-rays diffraction (XRD) showed that the selenium has a hexagonal crystal structure. Scanning electron microscopy (SEM) indicated that the selenium is distributed with uniform nuclei. The UV–Visible spectrophotometry revealed that the optical band gap (Eg) for the electrodeposited selenium is found to be 1.62 eV.

Comparative study of electrochemically-grown vanadium pentoxide nanostructures synthesized using differential pulse voltammetry, cyclic voltammetry, and chronoamperometry methods as the hole transport layer

Vanadium pentoxide (V2O5) nanostructures were grown on the ITO-coated glass slides using differential pulse voltammetry (DPV), cyclic voltammetry (CV), chronoamperometry (CA) methods, and utilized as the hole transport layer (HTL) in the construction of bulk heterojunction polymer solar cells (BHJ PSCs). The influences of the deposition time in the mentioned methods were investigated to find the best conditions to achieve the highest electrochemical performance from the deposited layer. The morphology of the electrodeposited nanostructures differed by changing the applied potential regime, and V2O5 nanorods (NRDs) were formed by the CV while V2O5 nanoparticles (NPs) formed using DPV and chronoamperometry. Simple adjustment of the applied potential regime and deposition time led to considerable structural and electrochemical changes of the resulting V2O5. Features of the electrochemically-grown V2O5 were compared with each other and with those of the V2O5 prepared using the hydrothermal method. The best sample in each series was selected in terms of suitable surface conductivity, high optical transparency and appropriate energy levels and applied as HTL in BHJ PSCs. Results revealed that the V2O5 sample prepared using DPV provided considerably better electrical, optical and electrochemical features. PSCs prepared based on this sample exhibited a higher power conversion efficiency (PCE) (~ 48%) and fill factor (~2%) than PSCs prepared based on V2O5 synthesized by the hydrothermal method. This was attributed to the high electroactive surface area (0.26±0.003 cm2), high charge mobility (2.44 × 10-4 cm2. V-1s-1) and excellent conductivity (0.03 mS.cm-1) of V2O5 NPs grown using DPV. The best cell provided an open circuit voltage of about 0.56 V, a short circuit current of 9.42 mA cm2, a fill factor of 65.3% and a power conversion efficiency of 3.40%. PCE of this cell was about 60% higher than that considered for the reference device prepared base on the PEDOT:PSS HTL.

Glucose nano biosensor with non-enzymatic excellent sensitivity prepared with nickel–cobalt nanocomposites on f-MWCNT

NiCo (Nickel-cobalt) nanoparticles were obtained by the chemical reduction method on functionalized multi-walled carbon nanotubes. After this process, chronoamperometry, cyclic voltammetry, and amperometric methods were used to investigate the electrochemical and electrocatalytic behavior of NiCo@f-MWCNT against glucose oxidation. In addition, the NiCo@f-MWCNT nanocomposites were analyzed by characterization techniques such as X-Ray Diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Transmission Electron Microscopy (TEM), and Atomic Force Microscopy (AFM) in terms of the morphological and atomic structure of prepared nanomaterials. The sensitivity and limit of detection the non-enzymatic glucose sensor (NiCo@f-MWCNT) were calculated as 10,015 μA/mM−1 cm−2 0.26 μM, respectively. As a result of these studies and experiments, the NiCo@f-MWCNT nanocomposite is a really good sensor and their stability showed that the current nanomaterials expressed to be new material for the electrochemical detection of glucose.

Rational design of PdCu nanoparticles supported on a templated Ni foam: The cooperation effect of morphology and composition for electrocatalytic oxidation of ethanol

In this study, with the goal of the production of a cost effective anode for ethanol oxidation, the surface of Ni foam is covered with templated PdCu nanoparticles via the galvanic replacement reaction. The use of the templating method results in the uniform formation of the spongiform bimetallic structure on the surface of Ni foam. The role of the templating method in the synthesis of a stable catalyst towards dealloying process is considered by the electrochemical pretreatment of t-PdCu/NF and PdCu/NF in H2SO4 solution. The excellent stability of t-PdCu/NF for ethanol oxidation in the alkaline media is proved by the achievement in the steady state after 14 s with survival of 60% current density and 12% increase in the current density after 100 consecutive cycles. The electrochemical impedance spectroscopy gives evidence that the templating method and elemental composition cooperate in the improvement of the reactant diffusion and charge transfer on the surface of the synthesized catalyst. Finally, the mechanism of the ethanol oxidation and the effect of morphology and composition on this mechanism are studied using the cyclic voltammetry and chronoamperometry methods.

Enhancing hydrogen production through anode fed-batch mode and controlled cell voltage in a microbial electrolysis cell fully catalysed by microorganisms

A microbial electrolysis cell (MEC) fully catalysed by microorganisms is an attractive technology because it incorporates the state-of-the-art concept of converting organic waste to hydrogen with less external energy input than conventional electrolysers. In this work, the impact of the anode feed mode on the production of hydrogen by the biocathode was studied. In the first part, three feed modes and MEC performance in terms of hydrogen production were evaluated. The results showed the highest hydrogen production under the continuous mode (14.6 ± 0.4), followed by the fed-batch (12.7 ± 0.4) and batch (0 L m−2 cathode day−1) modes. On one hand, the continuous mode only increased by 15% even though the hydraulic retention time (HRT) (2.78 h) was lower than the fed-batch mode (HRT 5 h). A total replacement (fed-batch) rather than a constant mix of existing anolyte and fresh medium (continuous) was preferable. On the other hand, no hydrogen was produced in batch mode due to the extensive HRT (24 h) and bioanode starvation. In the second part, the fed-batch mode was further evaluated using a chronoamperometry method under a range of applied cell voltages of 0.3–1.6 V. Based on the potential evolution at the electrodes, three main regions were identified depending on the applied cell voltages: the cathode activation (<0.8 V), transition (0.8–1.1 V), and anode limitation (>1.1 V) regions. The maximum hydrogen production recorded was 12.1 ± 2.1 L m−2 cathode day−1 at 1.0 V applied voltage when the oxidation and reduction reactions at the anode and cathode were optimal (2.38 ± 0.61 A m−2). Microbial community analysis of the biocathode revealed that Alpha-, and Deltaproteobacteria were dominant in the samples with >70% abundance. At the genus level, Desulfovibrio sp. was the most abundant in the samples, showing that these microbes may be responsible for hydrogen evolution.

Silicon Carbide Nanoparticles-Based Nanofibrous Membrane in Comparison With Thin-Film Enzymatic Glucose Sensor.

This work presents, silicon carbide nanoparticles (SiCNPs) embedded in a conductive polymer (CP) to be electrospun to fabricate a nanofibrous membrane and a thin-film. Electrochemical enzymatic glucose sensing mechanism of an electrospun nanofibrous membrane (ENFM) of SiCNPs in a CP compared to a spin-coated-thin-film (SCTF) of SiCNPs in a CP. Fiber alignment in the form of a matrix is a key factor that determines the physical properties of nanofiber membrane compared to thin-film. It is found that glucose sensing electrodes formed by a SiCNPs-ENFM has enhanced binding of the glucose oxidase (GOx) enzyme within the fibrous membrane as compared to a SiCNPs-SCTF. The SiCNPs-ENFM and SiCNPs-SCTF glucose sensing electrodes were characterized for morphology by using scanning electron microscopy (SEM) and for electrochemical activity by using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA) methods. SiCNPs-ENFM based glucose electrodes shown a detection range from a 0.5 mM to 20 mM concentration with a better sensitivity of [Formula: see text]/gmMcm2, and low limit of detection (LOD) 552.89 nM compared to SiCNPs-SCTF with sensitivity of [Formula: see text]/gmMcm2 and LOD of [Formula: see text]. The change in current level with SiCNPs-ENFM was ~14% contrast to ~75% with the SiCNPs-SCTF based glucose sensor over 50 days. The electrochemical analysis results demonstrated that the SiCNPs-ENFM electrode provides enhanced sensitivity, better limit of detection (LOD), and durability compared to SiCNPs-SCTF based glucose sensing electrode.

Incorporation of Fe in mixed CoCu-alkoxide hollow sphere for enhancing the electrochemical water oxidation performance

The promotion of water electrolysis performance heavily relies on the development of affordable and efficient electrocatalytic materials for the oxygen evolution reaction (OER). In this study, ternary Fe-substituted CoCu-glycerate microspheres (CoCuFe(X)-Gly) with cobalt (Co):copper (Cu):iron (Fe) atomic ratio of 2:1-X:X (X = 0.15, 0.3, 0.5, 0.8) have been prepared through facile template-free solvothermal method to examine their performance as alkaline OER catalyst. The results suggested that Fe incorporation could enhance the OER activity, and all Fe-modified samples showed lower overpotential with faster kinetic, as revealed by their Tafel slope and electrochemical impedance spectroscopy (EIS) analysis. Among the fabricated samples, CoCuFe(0.5)-Gly possessed the smallest overpotential of 317 mV at 10 mA/cm2 with 3.58-fold higher current density than that of Fe-free CoCu-Gly at the overpotential of 350 mV. Cyclic voltammetry (CV) disclosed that Fe incorporation imposed strong electronic interactions that facilitate the transformation of metal-glycerate surface into active oxyhydroxide species under anodic condition prevalent before oxygen evolution reaction. Using various characterization techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) method of surface area analysis, and thermogravimetric analysis (TGA), the physiochemical traits of samples have been carefully elucidated to determine the changes applied upon Fe substitution. Also, through Fe introduction, owing to the outward diffusion of ions to replace 2-propanol with glycerol, the solid microspheres partly become hollow which results in higher BET surface area and increase in accessible active sites. However, the evaluation of current density normalized by electrochemical active surface area (ECSA) indicates that the promotional effect of Fe was not solely related to the higher surface area but also because the intrinsic activity of Fe-modified samples has also been enhanced. The durability of optimal CoCuFe(0.5)-Gly catalyst has been examined using chronopotentiometry, chronoamperometry and potential cycling methods the findings of which suggest the good short-term and long-term stability of catalyst.

A reliable electrochemical approach for detection of sulphite with Tl-doped in Mn3O4 nanostructures and ionic liquid-modified carbon paste electrode

ABSTRACT In this work, we have designed and developed a new electrochemical sensing platform to determine sulphite, with the aid of a carbon paste electrode modified with thallium doped Mn3O4 nanostructures and ionic liquid (n-hexyl-3-methylimidazolium hexafluoro phosphate) (Tl-Mn3O4/IL/CPE). Electrochemical oxidation of sulphite at the Tl-Mn3O4/IL/CPE was investigated by the cyclic voltammetry (CV), linear sweep voltammetry (LSV), differential pulse voltammetry (DPV) and chronoamperometry (CHA) methods. The results of electrocatalytic activity proved that the Tl-Mn3O4/IL/CPE has electrocatalytic activity compared to unmodified CPE, Tl-Mn3O4/CPE and IL/CPE for sulphite oxidation. The experimental results showed the wide linearity range (0.03 to 235.0 μM) with lower value of detection (10.0 nM) for detection of sulphite. As expected, the proposed electrochemical sensor exhibits long time stability, excellent repeatability and reproducibility. In addition, this sensor exhibited high selectivity for the detection of sulphite in the presence of possible Interferences. The practical applicability of the modified electrode was examined in water samples with good recovery values. This facile and cost-effective method provides a novel strategy for monitoring of sulphite in real samples.