Electrocatalytic Behavior Research Articles

Developing TiCo2O4 spinel based on rGO nanosheet to enhance electrochemical performance of OER activity

The reduction of fossil fuel reserves and the deterioration of environmental conditions have led to a worldwide concern with producing significant amounts of energy in a sustainable manner. The production of electrocatalysts for the oxygen evolution reaction (OER) is imperative for widespread commercialization of water electrolyzers. The electrocatalysts must exhibit improved electrocatalytic behavior while being cost-effective. This work presents simple hydrothermal route for producing a TiCo2O4 nanostructure with a spherical morphology, which is supported on reduced graphene oxide sheets (rGO). The nanocomposite has been subjected to an investigation of its morphological, structural and electrochemical characteristics. This material exhibits promise for electrochemical water splitting due to its significant electroactive surface area, distinctive morphology and metal ions (M+) synergetic effect on its electrocatalytic performance. The nanostructure of TiCo2O4/rGO-has been observed to exhibit robust electrocatalytic activity, underscoring the significance of the present study. Additionally, presented are the enduring stability of the OER, along with the reduced overpotential (269 mV@10 mA cm−2), decreased Tafel slope (37.56 mV dec-1) with greater electrochemical active surface area. Our finding suggests that the TiCo2O4/rGO nanohybrid exhibited high electrocatalytic efficiency and can be utilized in diverse electrochemical applications.

Hydrothermal synthesis of NiS2@SnS2 nanohybrid for the water splitting application

The potential capabilities of stannous sulphide (SS) in the domain of the hydrogen evolution process (HER) have attracted significant interest. By employing a straightforward single-step hydrothermal method, we successfully boosted the HER performance of SnS2. This was achieved by fabricating a nanocomposite consisting of nickel sulphide (NS) and tin sulphide (SS) nanostructure. The resulting NS@SS nanocomposite shows the superior electrocatalytic behavior for the HER compared to pristine NS and SS material. The composite exhibited a morphology with two distinct phases, such as nanoparticles and nanorod structures that are responsible for good electrochemical properties. The NS@SS nanocomposite has several advantages for enhancing HER electroactivity, including a greater active surface area, increased edge-terminated structures, and better conductivity. The catalyst has high stability in alkaline solutions and demonstrates a low overpotential (ɳ) of 155 mV@ 10 mA cm−2 with a Tafel slope of 34 mV dec−1. The current results show that the NS@SS nanocomposites are a potential candidate for the energy production materials and energy conversion system.

Hydrazine electrooxidation performance of cyano-substituted indole derivatives as organic anode catalyst

Here we present the new EWG-substituted indole derivatives, namely 2-((5-(1-methyl-2-phenyl-1 H-indol-3-yl)thiophen-2-yl)methylene) malonitrile (IPTM), 2-((5-(1-methyl-2-phenyl-1 H-indol-3-yl)furan-2yl)methyl)malonitrile(IPFM) and 2-((4-(1-methyl-2-phenyl-1 H-indol-3-yl)benzylidene) malonitrile (IPPM) was synthesized by using Sonogashira coupling, electrophilic cyclization, Suzuki-Miyaura coupling and condensation reactions. The isolated yields were obtained as 86 %, 71 %, and 69 % yields, respectively. Cyclic voltammetry(CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) were used for the electrochemical measurements to observe the electrocatalytic behavior of IPTM, IPFM and IPPM. The results exhibited that the highest-performance organic-based catalyst was 2.601 mA/cm2 (0.073 mA/mg) for IPPM which could be a good candidate as a metal-free electrocatalyst for hydrazine electrooxidation.

Nanostructured NiMoO4 electrode materials for efficient oxygen evolution reaction

Bifunctional electrocatalysts derived from earth-abundant transition metals are a promising substitute for noble metals in general water electrolysis, but their low activity and short durability limit their application. Herein, a nickel molybdate nanoparticles decorated on nickel foam (NiMoO4/NF NPs) electrode was fabricated by a facile hydrothermal method at three different time intervals (6, 12, and 24 h) and verified for the oxygen evolution reaction (OER). The constructed electrodes exhibited high OER activity in 1.0 M KOH with overpotentials of 315 mV, 290 mV and 320 mV for NiMoO4-6 h, NiMoO4-12 h, and NiMoO4-24 h, respectively. In addition, the NiMoO4-12 h electrodes displayed remarkable durability with a negligible reduction of 1.28 % at a current density of 10 mA cm−2 for 200 h. This research work delivers a new pathway to improve the electrocatalytic behaviour of the catalysts by synergistically moderating the inherent electrical conductivity, efficient surface moieties, and surface reaction.

Graphene nanoplatelets-polyaniline composite for the detection of cortisol

In this study, a highly selective Graphene oxide (GO)-Polyaniline (PANI) modified glassy carbon electrode (GCE) was fabricated and its electrocatalytic behaviour towards the electro-reduction of cortisol in human saliva was investigated. The synthesized nanocomposites were characterized using different analytical approaches. The electrochemical study of the PANI-GO modified electrode was analyzed by employing a cyclic Voltammetry (CV) study. The outcomes demonstrated a substantial enhancement in the reduction and oxidation current peaks of the modified GCE as associated to bare GCE, GO/GCE and PANI/GCE. Along with enhanced electronic properties, the biosensor displays the good selectivity and sensitivity, good reproducibility (95 %, n = 8), high stability (maintaining more than 95 % response even after 11 weeks of storage at −20C, 50 cycles), a wide linear range (100μ-10 mM) and small detection limit (30 μM). The utilization of PANI-GO in the electrode modification process may be attributed to these positive outcomes, given some of the amazing characteristics of the composite, such as its larger surface area, outstanding electrical conductivity, and good electrocatalytic behavior. Furthermore, the PANI-GO modified GCE was successfully validated by detecting cortisol in real human saliva samples using cyclic voltammetry, highlighting the effectiveness of the PANI-GO composite for non-invasive electrochemical cortisol detection.

Enhanced oxygen evolution reaction of electrodeposited Functionally-Graded Ni-Cu-Fe coating

This study aimed to use a functionally graded (FG) Ni-Cu-Fe coating as an electrocatalyst for oxygen evolution reaction (OER) applications. The coating was applied on a mild carbon steel substrate by an electrodeposition technique, with the current density being progressively increased from 0.5 A/dm2 to 5 A/dm2 at a steady rate of 0.2 (A/dm2)/min during the coating operation. Using this specific method, the Ni content of the FG Ni-Cu-Fe coating changed along the cross-section when increasing the current density, 17 % more than the constant current coating. This technique also affected the surface morphology of the FG Ni-Cu-‌Fe coating and changed it from cauliflower to micro/nanocones when the current density was linearly increased, enhancing active sites significantly and thereby improving electrocatalytic activity. The coating's electrocatalytic behavior was studied by electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), and cyclic voltammetry (CV). results showed that the FG Ni-Cu-Fe coating had the smallest overpotential (134 mV) at the current density of 10 mA.cm−2. Also, it had the smallest Tafel slope (24.3 mV.dec− 1) and smallest resistance (598 Ω.cm2) compared to all of the other coatings. The FG Ni-Cu-‌‌Fe coating had higher OER performance because of high Ni content, micro/nanocones morphology with many active sites, and FG nature. The FG Ni-Cu-Fe coating is finally concluded to be a promising and economical catalyst with high OER activity.

Promoting effect of TiVC MXene on cathodic electrogenerated chemiluminescence of Ru(bpy)32+ and its application in the sensitive detection of sulfite.

The enhanced cathodic ECL of Ru(bpy)32+ at a bimetallic element MXenes (TiVC MXene) modified electrode in neutral aqueous conditionis reported. TiVC MXene significantly catalyzed the oxygen reduction reaction (ORR) as well as the electrochemical reduction of Ru(bpy)32+ to produce reactive oxygen species and Ru(bpy)3+. The obtained hydroxyl radical (OH∙) not only oxidized Ru(bpy)3+ to generate Ru(bpy)32+* and emit light through coreactant pathway, but also oxidized Ru(bpy)32+ to Ru(bpy)33+, which caused an annihilation ECL reaction. As a result, two pathways occurred simultaneously to generate strong cathodic ECL signal. Sulfite removes the dissolved oxygen in water and reduces the occurrence of ORR, which prohibits the generation of OH∙ to decrease the ECL signal. The decrement of ECL intensity varied linearly with the concentration of sulfite in the range 2nM to 50μM with a detection limit of 0.14nM (3σ). The proposed sensor exhibited good analytical performance, and could be used in the detection of sulfite in real samples. The results revealed that the electrocatalytic behavior of TiVC MXene is the key factor for strong cathodic Ru(bpy)32+ ECL, which provides new application in ECL sensing field.

Electrochemical Sensor Based on Electrodeposited Zinc-Aluminium Layered Double Hydroxide Modified Glassy Carbon Electrode for Chlorpromazine Sensing

Chlorpromazine functions as a potent dopamine D2 receptor antagonist, leading to adverse motor-related effects encompassing cataracts, musculoskeletal disorders, alterations in eyelid pigmentation, muscle contractions, and tremors-addressing the need for a reliable analytical tool, an electrodeposited thin film was synthesized on a glassy carbon electrode (GC) surface. This film comprised zinc-aluminium layered double hydroxide (Zn-Al LDH), with nitrate ions intercalated between the LDH layers. The electrocatalytic behavior of the resulting electrode (GC/Zn-Al LDH) in the oxidation and reduction of nitrogen and sulfur atoms within the thiazine ring structure of chlorpromazine was systematically studied using cyclic voltammetry. Evaluation of the electrode’s analytical response through diverse electroanalytical techniques demonstrated that the square wave voltammetry-assisted electrochemical sensor displayed a broad detection range for chlorpromazine (1 × 10−4 to 1 mM), with a sensitivity of 91.86 μA mM−1 and an impressive low detection limit of 16 × 10−6 mM. Furthermore, the performance of the developed electrode was assessed in detecting and quantifying chlorpromazine levels in simulated human urine samples through recovery studies. The results indicated satisfactory recovery rates, affirming the efficacy of the Zn-Al LDH-modified GC electrode. Noteworthy features of the electrochemical sensor included high surface coverage, improved electron transfer rate, reliable repeatability, and exceptional reproducibility. These characteristics collectively contribute to the sensor’s popularity for accurately detecting and quantifying of chlorpromazine in real-world samples.

A new multifunctional electrocatalyst based on PbS nanostructures decorated with graphene/polyaniline-modified glassy carbon electrode for selective detection of non-steroidal anti-inflammatory drug naproxen

Naproxen (NAP), a well-known anti-inflammatory drug, has also been considered for its antiviral prospective and acceptable potential for in vitro activity against serious respiratory syndrome-related coronavirus (SARS-CoV) and anti-influenza activity. However, designing a selective, sensitive and efficient electrocatalyst for the determination of NAP is still a great challenge. In this research, a new electrocatalytic sensor was constructed for the electrochemical recognition of NAP by a glassy carbon electrode modified with PbS nanostructures incorporated graphene/polyaniline nanocomposite. The synthesized samples were characterized by physicochemical analyses like EDS, XRD, FTIR, FESEM, and PL. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV) were carried out to examine the electrocatalytic behavior of the modified electrodes. The EIS plot obviously demonstrated rapid electron transport at low frequencies for the PbS/graphene/PANI/GC electrode. It was observed that the PbS/graphene/PANI/GC electrode exhibited better-defined oxidation peaks, and greater peak currents for NAP detection compared to other electrodes. Under the optimum conditions, the proposed PbS/graphene/PANI nanoplatform provided a reliable linear range of 1 to 100 µM with a detection limit as low as 0.08 μM. Meanwhile, the PbS/graphene/PANI electrode possessed acceptable selectivity, good repeatability with an RSD of about 2.6 %, and a reduction of about 3 % after two weeks, and long-term stability of about 97 % of its original response for the recognition of NAP. Furthermore, the constructed electrode demonstrated NAP detection in real samples, such as human plasma and urine with good recoveries ranging from 98.8 % to 99.9 %, suggesting its promising prospects in clinical diagnostics.

Synthesis of peripheral thiol functionalized (NiII) phthalocyanine and its attachment on Au electrode for electrochemical determination of L-DOPA

This paper presents the synthesis, characterization, and electrocatalytic behavior of peripheral thiol-functionalized nickel(II) phthalocyanine (4β-NiIITTPc). The complex was synthesized and characterized using MALDI-TOF mass spectra, UV–visible, and FT-IR spectroscopies. Upon self-assembly on the Au surface from dimethylformamide solution, 4β-NiIITTPc forms via the formation of an Au-S bond. The attachment onto the Au surface was verified through Raman spectroscopy and cyclic voltammetry, with characteristic bands at 2572 and 250 cm−1 corresponding to -SH and Au-S stretching vibrations, respectively. Notably, the -SH stretching indicates that not all four -SH groups of 4β-NiIITTPc are involved in chemisorption. The resulting self-assembled film on the Au electrode exhibits well-defined oxidation peaks at +0.34 V and +0.56 V, corresponding to NiIII/NiII and NiIIPc−1/NiIIPc−2, respectively. The surface coverage was estimated from the charge associated with NiII/NiIII oxidation, yielding 1.01 × 10−10 mol cm−2. Finally, the electrocatalytic activity of the self-assembled monolayer (SAM) of 4β-NiIITTPc on Au electrodes was assessed by studying the oxidation of 3,4-dihydroxy-1-phenylalanine (L-dopa) as a probe. The SAM-modified electrode not only shifts the oxidation potential of L-dopa to a less positive potential but also enhances the oxidation current and mitigates electrode surface fouling compared to the bare Au electrode.

Highly transparent and efficient Pt/CeOx counter electrodes for bifacial dye-sensitized solar cells

In this research, we introduce a pioneering approach for enhancing the electrocatalytic performance of counter electrodes (CEs) in dye-sensitized solar cells (DSSCs) by synthesizing Pt/CeOx hybrid nanocatalysts through a refined polyol reduction technique. This method facilitates the accurate production of Pt nanoparticles supported on ceria, leveraging their strong metal-oxide interactions. X-ray photoelectron spectroscopy (XPS) was employed to confirm the co-presence of both metallic and oxidized states of Pt, as well as the mixed valence states of ceria within these nanostructures. The electrocatalytic behavior of these nanocatalysts was rigorously evaluated using cyclic voltammetry (CV), Tafel polarization analyses, and electrochemical impedance spectroscopy (EIS). We identified an optimal Pt/Ce ratio of 1:0.1, which significantly enhanced the kinetics of the iodine reduction reaction (IRR), a crucial factor for efficient DSSC operation. Photovoltaic testing under one-sun AM 1.5 G conditions demonstrated that DSSCs with the optimized Pt/CeOx CEs exhibited a 10 % increase in power conversion efficiency (PCE) comparted to control cells. This study highlights the effectiveness of Pt/CeOx hybrid nanocatalysts in improving bifacial DSSC performance, combining the catalytic strengths of platinum with the unique properties of ceria.

Spherical Silver Nanoparticles Located on Reduced Graphene Oxide Nanocomposites as Sensitive Electrochemical Sensors for Detection of L-Cysteine.

A new, simple, and effective one-step reduction method was applied to prepare a nanocomposite with spherical polycrystalline silver nanoparticles attached to the surface of reduced graphene oxide (Ag@rGO) at room temperature. Equipment such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR) was used to characterize the morphology and composition of the Ag@rGO nanocomposite. A novel electrochemical sensor for detecting L-cysteine was proposed based on fixing Ag@rGO onto a glassy carbon electrode. The electrocatalytic behavior of the sensor was studied via cyclic voltammetry and amperometry. The results indicate that due to the synergistic effect of graphene with a large surface area, abundant active sites, and silver nanoparticles with good conductivity and high catalytic activity, Ag@rGO nanocomposites exhibit significant electrocatalytic activity toward L-cysteine. Under optimal conditions, the constructed Ag@rGO electrochemical sensor has a wide detection range of 0.1-470 μM for L-cysteine, low detection limit of 0.057 μM, and high sensitivity of 215.36 nA M-1 cm-2. In addition, the modified electrode exhibits good anti-interference, reproducibility, and stability.

CeO2-supported Pt nanoclusters for improved electrochemical oxidation of methanol

Developing highly durable and active Pt-supported catalysts is currently the most prominent and practicable electrocatalyst design strategy for direct methanol fuel cells (DMFC) due to their high electrocatalytic stability and activity. Herein, we fabricated CeO2 nanorods with tiny Pt nanoparticles that possess good electrocatalytic behavior for methanol oxidation reaction (MOR). In addition, the presence of Ce3+ and small Pt nanoparticles (3.46 nm) enhanced strong metal interaction, facilitating the formation of oxygen vacancies on the CeO2 surface to boost the MOR performance. Hence, the Pt-CeO2 catalyst revealed high mass activity (1414.0 mA mg−1) and areal-specific activity (1.615 mA cm−2) towards MOR in an acidic electrolyte, which was three times that of the 20% Pt/C catalyst (545.4 mA mg−1 and 0.856 mA cm−2). Besides, the Pt-CeO2 catalyst exhibited excellent performance of MOR in an alkaline electrolyte and retained 90.44% of its initial mass activity after 5000 cycles due to the unique morphology and synergistic effects between Pt and CeO2. Pt-CeO2 is regarded as a promising MOR electrocatalyst for DMFC applications.Graphical

Nano-micro 2D/3D SnO2 semiconductor ultrahigh sensitive sensors for electrochemical sensing of hydrogen peroxide

Detection of H2O2 levels is highly in demand as they are related with several environmental and medical applications. H2O2 is a reactive oxygen species that plays a crucial role in various cell functions thus it is considered as a potential biomarker. Novel 3D/2D SnO2 micro-nanostructures (with dimensions of 3D: B≈1 µm×L≈10 µm×T≈1 µm; 2D structures ranging<100 nm) modified on glassy carbon electrodes (SnO2/GCE) displayed an electrocatalytic redox behaviour against H2O2 on an alkaline based electrolyte medium illustrated using a three-electrode system. This is the first time hybrid morphology with 2D/3D structures of SnO2 is developed. SnO2/GCE was tested for H2O2 concentration ranging from 2.45 to 24.5 μM. The LOD of the sensor was observed to be 4.09 μM within the measured concentration limits. The sensors exhibited an ultra-high sensitivity value of 108 mA.mM−1.cm−2. All the linear fits are exhibiting higher accuracy with R2 of 0.99. Hybrid morphology of SnO2 acts as promising sensing material independently for detection of H2O2 even in alkaline medium with pH of 12. Also, it should be noted that electrochemical sensing of SnO2 alone is tested depicting better properties whereas commonly hybrid, composite materials are used for sensing applications.

A new Co-doped PbO2 anode for copper electrowinning: Electrochemical and morphological characterization

Anodic electrodeposition was used to create a high catalytic activity Co-doped PbO2 composite coating on Ti substrate, in order to reduce the overpotential and raising the electrocatalytic activity for oxygen evolution during the copper electrowinning process. The temperature, composition, and current density of the electrolyte were investigated in order to produce a composite anode with the best electrocatalytic behavior, stability, and efficiency in the electrowinning process. Scanning electron microscopy (SEM) was utilized to investigate the morphology of the coating, and electrowinning, cyclic voltammetry (CV), and the accelerated life time test (ALT) were employed to evaluate the electrodes' electrochemical behavior. The ideal conditions in this investigation involved 65 g.L−1 cobalt nitrate with a 5 mA.cm−2 current density at 65 °C for the electrodeposition of Co-doped PbO2 coating. Furthermore, the potential for oxygen evolution of the PbO2-CoOx anode was found to be approximately 180 and 220 mV lower than that of the PbO2 and Pb-Ca-Sn anodes, respectively, based on the results of the electrochemical test. The ALT test results showed that the PbO2-CoOx anode had a significantly lower initial cell voltage than the Pb-Ca-Sn and PbO2 anodes; however, this value increased after 165 h due to the anode's mechanical breakdown. The results showed that Cu electrowinning efficiency for Pb-Ca-Sn, PbO2, and PbO2-CoOx was 91.9 %, 98.4 %, and 100 % respectively.

Construction of hierarchical NiCo2 S4 /2D-Carbyne nanohybrid onto nickel foam for high performance supercapacitor and non-enzymatic electrochemical glucose sensor applications.

Synthesising and designing pseudocapacitive material with good electrochemical and electrocatalytic behaviour is essential to use as supercapacitor as well as non-enzymatic glucose sensor electrode. In this work, NiCo2 S4 nanoparticles decorated onto the 2D-Carbyne nanosheets are achieved by the solvothermal process. The as-prepared NiCo2 S4 @2D-Carbyne provides rich reaction sites and better diffusion pathways. On usage as an electrode for supercapacitor application, the NiCo2 S4 @2D-Carbyne exhibits the specific capacitance of about 2507 F g-1 at 1 A g-1 . In addition, the fabricated hybrid device generates an energy density of 52.2 Wh kg-1 at a power density of 1.01 kW kg-1 . Besides, the glucose oxidation behaviour of NiCo2 S4 @2D-Carbyne modified GCE has also been performed. The diffusion of glucose from the electrolyte to the electrode obeys the kinetic control process. Furthermore, the fabricated NiCo2 S4 @2D-Carbyne non-enzymatic glucose sensor exhibits a limit of detection of about 34.5 μM with a sensitivity of about 135 μA mM-1 cm-2 . These findings highlight the need to design and synthesis electrode materials with adequate electrolyte-electrode contact, strong structural integrity, and rapid ion/electron transport.

Calcium-, magnesium-, and yttrium-doped lithium nickel phosphate nanomaterials as high-performance catalysts for electrochemical water oxidation reaction

Abstract Electrochemical water oxidation reaction (WOR) lies among the most forthcoming approaches toward eco-conscious manufacturing of green hydrogen owing to its environmental favors and high energy density values. Its vast commoditization is restricted by high-efficiency and inexpensive catalysts that are extensively under constant research. Herein, calcium, magnesium, and yttrium doped lithium nickel phosphate olivines (LiNi1−x M x PO, LNMP; x = 0.1–0.9; M = Ca2+, Mg2+, and Y3+) were synthesized via non-aqueous sol-gel method and explored for catalytic WOR. Lithium nickel phosphates (LNP) and compositions were characterized via Fourier transform infrared, scanning electron microscopy, X-ray diffraction, and energy dispersive X-ray diffraction techniques for the structural and morphological analyses. Glassy carbon electrode altered with the LNMPs when studied in a standard redox system of 5 mM KMnO4, displayed that yttrium doped LNP, i.e. LNYP-3 exhibits the highest active surface area (0.0050 cm2) displaying the lowest average crystallite size (D avg) i.e. ∼7 nm. Electrocatalytic behavior monitored in KOH showed that LNMP-2 offers the highest rate constant “k o,” value, i.e. 3.9 10−2 cm s−1 and the largest diffusion coefficient “D o,” i.e. 5.2 × 10−5 cm2 s−1. Kinetic and thermodynamic parameters demonstrated the facilitated electron transfer and electrocatalytic properties of proposed nanomaterials. Water oxidation peak current density values were indicative of the robust catalysis and facilitated water oxidation process besides lowering the Faradic onset potential signifying the transformation of less LNP into more conducive LNMP toward water oxidation.

Ni-Xides (B, S, and P) for Alkaline OER: Shedding Light on Reconstruction Processes and Interplay with Incidental Fe Impurities as Synergistic Activity Drivers.

Ni-Xides (X = B, P, or S) exhibit intriguing properties that have endeared them for electrocatalytic water splitting. However, the role of B, P, and S, among others, in tailoring the catalytic performance of the Ni-Xides remains vaguely understood, especially if they are studied in unpurified KOH (Un-KOH) because of the renowned impact of incidental Fe impurities. Therefore, decoupling the effect induced by Fe impurities from inherent material reconstruction processes necessitates investigation of the materials in purified KOH solutions (P-KOH). Herein, studies of the OER on Ni2B, Ni2P, and Ni3S2 in P-KOH and Un-KOH coupled with in situ Raman spectroscopy, ex situ post-electrocatalysis, and online dissolution studies by ICP-OES are used to unveil the distinctive role of Ni-Xide reconstruction and the role of Fe impurities and their interplay on the electrocatalytic behavior of the three Ni-Xide precatalysts during the OER. There was essentially no difference in the OER activity and the electrochemical Ni2+/Ni3+ redox activation fingerprints of the three precatalysts via cyclic voltammetry in P-KOH, whereas their OER activity was considerably higher in Un-KOH with marked differences in the intrinsic activity and evolution of the Ni2+/Ni3+ fingerprint redox peaks. Thus, in the absence of Fe in the electrolyte (P-KOH), neither the nature of the guest element (B, P, and S) nor the underlying reconstruction processes are decisive activity drivers. This underscores the crucial role played by incidental Fe impurities on the OER activity of Ni-Xide precatalysts, which until now has been overlooked. In situ Raman spectroscopy revealed that the nickel hydroxide derived from Ni2B exhibits higher disorder than in the case of Ni2P and Ni3S2, both exhibiting a similar degree of disorder. The guest elements thus influence the degree of disorder of the formed nickel oxyhydroxides, which through their synergistic interaction with incidental Fe impurities concertedly realize high OER performance.

Polyaniline based highly selective electrochemical sensor for ascorbic acid determination: Performance studies towards real sample analysis

The electrocatalytic behavior of polyaniline (PAni) towards the electro-oxidation of L-ascorbic acid (L-AA) was studied by using cyclic voltammetry. PAni synthesized by oxidative polymerization method, and characterized by using high resolution-transmission electron microscopy (HR-TEM), scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM-EDAX) confirms large globular structures, X-ray diffraction (XRD) analysis revealed that PAni with amorphous nature, whereas Fourier-transform infrared spectroscopy (FTIR) of PAni shows C-N stretching, X-ray photoelectron spectra (XPS) attributes the peaks C1s, N1s and O1s. UV–visible spectra revealed PAni is conducting and its Brunauer–Emmett–Teller (BET) surface area is 343.67 m2/g demonstrates it has high surface area and good adsorption ability. The PAni electrocatalyst showed an excellent selectivity towards L-AA in presence of different inorganic and biological expedients under similar conditions. A limit of detection (LOD) and limit of quantification (LOQ) were calculated found to be 5.1 µM and 17.2 µM respectively. Furthermore, the electrocatalyst activity towards L-AA were also validated for real sample analysis like lemon juice and vitamin-C tablet by quantifying the L-AA. The exceptionally higher conductivity and good electrocatalytic performance of PAni make it a promising material for sustainable energy generation and environmental protection without relying on metals or harmful chemicals.

Electrocatalytic behavior of Ni–Mo alloy electrodeposited from deep eutectic solvents-assisted plating baths: electrochemical impedance spectroscopy study

The electrocatalytic behavior of electrodeposited Ni and Ni–Mo alloy coatings in the hydrogen evolution reaction in a 1 M NaOH aqueous solution was investigated by means of the electrochemical impedance spectroscopy method. The electrochemical deposition of electrocatalytic coatings was carried out using electrolytes based on deep eutectic solvents (eutectic mixtures of choline chloride with ethylene glycol or urea). To simulate the recorded Nyquist plots reflecting the electrocatalytic performance of deposited coatings, a modified Armstrong-Henderson equivalent circuit was employed, which accounts for the involvement of adsorbed intermediates in the reaction. The equivalent circuit included three polarization resistances and three constant phase elements, allowing for the consideration of the localization of the electrochemical process on different surface microdomains. It was found that the electrocatalytic activity of nickel coatings deposited from deep eutectic solvents exceeded the activity of nickel fabricated in an aqueous electrolyte. The increase in molybdenum content in the coating was shown to enhance electrocatalytic activity. It was established that the main reasons for improving the electrocatalytic properties of the Ni–Mo alloy coatings are structural-morphological factors (increase in the degree of microheterogeneity of the surface and the development of the surface area available for electrochemical reaction) and the formation of a favorable electronic structure of the metal, leading to the acceleration of the rate-determining Volmer step.