Electrocatalysis最新文献

Due to its layered structure and appropriate electronic configuration, two-dimensional MoS₂ has been considered a reliable and inexpensive electrocatalyst and electrode material for the oxygen reduction reaction (ORR). Additionally, the MoS₂ and reduced graphene oxide (rGO) structure can act as a good host for other nano-catalysts. However, the catalytic activity of pristine MoS₂ is not as effective as the industrial targeted values. In this work, nickel-MoS₂ (Ni/MoS₂) and Ni/MoS₂-rGO composites are synthesized and evaluated as catalysts for ORR at the cathode. Electrochemical studies using a rotating disk electrode system confirmed that the as-synthesized catalyst exhibits good electrocatalytic activity to ORR in alkaline media (0.1 M KOH) and followed the desirable 4-electron transfer process. Ni/MoS₂-rGO composite displays a current density of − 11.1 mA/cm² and half-wave and onset potentials of 0.74 V and 0.87 V, respectively, at 2400 rpm, whereas the bare MoS₂ shows the values of limiting current density, half-wave potential, and onset potential of − 5.8 mA/cm², 0.61 V, and 0.79 V, respectively. Numerous highly active Mo sites, high conductivity, and high specific surface area in MoS₂-rGO make it a novel catalyst material for ORR. Ni further enhances conductivity and is involved in electrochemical reactions. The onset potential slightly shifts towards the lower value after the potential cycling, whereas the limiting current density decreases by ≈9.0% for Ni/MoS₂-rGO, which shows its good stability in alkaline media. Therefore, Ni/MoS₂-rGO composite can be a good candidate for electrode catalyst material for alkaline fuel cells.

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Recently, transition metal-based electrocatalysts have shown significant promise in promoting the oxygen evolution reaction (OER) as a result of their ample availability, tunable electronic properties, and catalytic capabilities. This study presents the synthesis of a transition metal-based electrocatalyst, featuring Co and Ni nanoparticles grown on Ti foil (CoNi@Ti). These nanoparticles are doped with Mn and Fe using with single-step in-situ chronoamperometry (CA) electrodeposition technique, resulting in the production of the Fe-MnCoNi@Ti nano-flower material. The results show that the Fe-MnCoNi@Ti nano-flower, with an overpotential of 261.6 mV, is an efficient electrocatalytic system for OER, achieving 10 mA cm⁻² and a Tafel slope of 114.3 mV dec⁻¹ in alkaline media. The comparison of the electrocatalytic performance of Fe-MnCoNi@Ti with other materials prepared in the same electrodeposition techniques and with the state-of-the-art materials indicated that our nano-flower material has comparable performance on its electrocatalytic properties for OER. In addition, the Turnover frequency (TOF) value highlights the high intrinsic activity of Fe-MnCoNi@Ti in catalyzing the OER. The stability test is also carried out by applying an overpotential of 400 mV with respect to the OER for 12 h of CA run, and it is found that Fe-MnCoNi@Ti has good stability for OER in alkaline conditions. The experimental results indicate that decorating Coniston nano-flower with Fe and Mn as dopant materials via electrodeposition technique is a simple one-step process, which led to better electrocatalytic performance of the material for the OER in alkaline media.

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Zn-ion batteries (ZIBs) are gaining attention due to their low cost, high capacity and efficiency, and strong cycling stability; nevertheless, further research is required to establish suitable cathode materials for the intercalation of Zn ions. Due to the layered structure, vanadium oxide–based materials are considered promising cathode materials of ZIB devices using gel polymer electrolytes (GPEs). The GPEs are considered a good alternative to liquid electrolytes due to their flexibility, leakage-free nature, and reduced Zn corrosion in Zn-based batteries. This work presents a carboxymethylcellulose and polyvinyl alcohol polymer matrix-based gel polymer electrolyte for applications in ZIBs for the first time. The polymer matrix shows an uptake of 150 wt% after immersion in 2 M ZnSO₄ electrolyte solution for 50 h. The as synthesized GPE has an ionic conductivity of 0.6 × 10⁻² cm⁻¹Ω⁻¹ and a thickness of 120 µm. The electrochemical results of the fabricated ZIB device fabricated using V₃O₇.H₂O cathode material exhibit a high specific capacity of 505 mAh/g at 0.1 A/g current density.

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A bimetallic Sb-Pd electrocatalyst was prepared through a versatile two-step electrodeposition method using chronopotentiometry, i.e., a controlled amount of Sb was electrodeposited onto glassy carbon (GC) electrode followed by electrodeposition of Pd to obtain desired Sb-Pd ratio. The synthesized electrocatalyst can be used as an anode catalyst for the methanol oxidation reaction (MOR), a prime fuel for direct methanol fuel cells (DEFCs). A morphological analysis of the Sb, Pd, and Sb-Pd electrocatalysts was performed by scanning electron microscopy (SEM) technique. The electrochemical properties of the Pd and Sb-Pd catalysts were evaluated using cyclic voltammetry (CV) and chronoamperometry (CA) in an alkaline electrolyte containing Na⁺ or Li⁺ cations. Compared to Pd alone, the Sb-Pd catalyst showed a twofold increase in peak current density and improved MOR kinetics. Both investigated catalysts exhibited higher poisoning tolerance in the solution containing Na⁺, implying that the product distribution in MOR depends on the alkali metal cation of the supporting electrolyte. The peak current of MOR at Pd and Sb‒Pd catalysts in the solution with Li⁺ cations is 1.4 times higher compared to the values obtained in the solution with Na⁺ cations, indicating the impact of the nature of alkali metal cations which arises from the formation of OH_ad ‒ cation clusters and the electronic interaction between CO_ad and OH_ad ‒ cation clusters. The presence of Sb in the structure of the bimetallic catalyst provides a lower susceptibility to the poisoning and consequently enhances MOR performances regarding the Pd catalyst.

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In this study, a simple, cost-effective and eco-friendly method was performed for the production of silver nanoparticle decorated reduced graphene oxide (rGO-Ag) nanocomposite using Onosma bracteosa leaf extract as reducing and stabilizing agent. The structure of the synthesized rGO-Ag nanocomposite was characterized by UV–Vis, XRD, SEM, TEM, EDX, and XPS. The synthesized rGO-Ag nanocomposite was used to fabricate an electrochemical sensor (rGO-Ag@GCE) for the determination of hydrogen peroxide. Electrochemical reduction of hydrogen peroxide was performed using DPV on rGO-Ag@GCE in 0.1 M PBS. The rGO-Ag@GCE exhibited good response in the linear concentration range of 25 µM to 800 µM, with a LOD of 0.11 µM. Amperometric measurements showed that the prepared sensor did not have a significant response to interfering species. Moreover, analysis of real samples demonstrated the potential of rGO-Ag@GCE as an electrochemical sensor for detecting hydrogen peroxide in commercial milk samples.

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The unusual electrochemical, catalytic, and electronic properties of conductive polymer composites with metal oxides, owing to their synergistic effects, have attracted continued interest in the past decade for diverse applications in electroanalysis and electrocatalysis. Herein, we present a novel method for indirect determination of diclofenac (DCF) sodium using a PANI|In₂O₃ composite. A glassy carbon electrode (GCE) modified with a thin PANI|In₂O₃ layer was synthesized by cyclic voltammetry (CV) from a 0.3 M H₂SO₄ solution. Electrochemical impedance spectroscopy (EIS) measurements demonstrated that the PANI|In₂O₃ composite has a significantly higher R_ct value 624.0 Ω than the pure polyaniline film (14.0 Ω). CVs of bare GCE demonstrated the irreversible oxidation of diclofenac, characterized by an anodic peak at a potential of 0.6 V. Differential pulse voltammograms (DPVs) of DCF on a GCE|PANI electrode showed two pronounced anodic peaks (j_pa), which were responsible for the electrochemical oxidation of polyaniline (I) and oxidation of DCF (II). Modification with In₂O₃ dramatically decreased the current density of peak II by inhibiting the oxidation of DCF, and on the contrary, it increased the intensity of peak I tens of times. The GC|PANI|In₂O₃ electrode can be used as an electrochemical sensor for the determination of diclofenac at low concentrations between 1 × 10^–6 M to 1 × 10^–4 M, and j_pa – C_DCF has a correlation coefficient of 0.95. The GC|PANI|In₂O₃ material exhibited a limit of detection of 181 nM and a linear range of 1–100 µM for the DCF sensor.

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The reliance of carbon black as catalyst support for Pt in PEM fuel cell has posed a major challenge in its durability as carbon blacks are highly prone to corrosion. As an alternative, CNTs, CNFs, and graphene are explored as catalyst support, however at the expense of tedious synthesis procedure and production cost. So to combat this issue, a facile flame pyrolysis route was adopted to produce carbon nano-onions using eco-friendly corn oil. Further modification in the carbon nano-onions exhibited better corrosion resistance in comparison to carbon black (Vulcan XC-72R). Also, a systematic approach was adopted towards developing a durable electrocatalyst which was designed to withstand harsh fuel cell operating conditions. The electrocatalyst was successfully analyzed using stringent standard testing protocols (< 40% ECSA loss). Among all the electrocatalyst studied, Pt/fOC exhibited only 37.1% loss in electrochemical active surface area (ECSA) after 5000 cycles, thus indicating its excellent durability. A full cell was also constructed with Pt/fOC as cathode electrocatalyst which showed a maximum power density of 365 mW cm⁻², comparable to commercial Pt/C (367 mW cm⁻²). To the best of our knowledge, this is the first study on the application of corn oil derived carbon nano-onions as catalyst support for PEM fuel cells.

Enhancement of the oxygen reduction reaction (ORR) activity is an important subject for the development of fuel cells. In this study, we prepared the n(111)-(111) series of Pt₃Co single crystal electrodes using an induction heating furnace and investigated the ORR in 0.1 M HClO₄ using the rotation disk electrode (RDE). The specific activity of the ORR (j_k) increased monotonously with increasing terrace width n on the n(111)-(111) series of Pt₃Co, showing the highest activity on Pt₃Co(111). The value of j_k of Pt₃Co(111) was 59-fold higher than that of Pt(111) at 0.95 V(RHE). This trend was different from those of the same series of Pt, Pt₃Co, and Pt₃Ni reported previously. Furthermore, the ORR activity was improved on all electrodes by adding melamine to the electrolytic solution. Melamine was preferentially adsorbed at the terrace edge. Pt₃Co(553) n = 5 showed the highest activity. The values of j_k at 0.95 V(RHE) were 23- and 3.3-fold higher than those of Pt(553) n = 5 and Pt₃Co(553) n = 5 without melamine modification, respectively. The durability of Pt₃Co(553) n = 5 with melamine was improved 8.0-fold.

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Methanol has potential to replace conventional fuels. But its popularity is hindered by lower kinetics of electrode reactions, lower surface area, CO poisoning of catalysts, and higher cost of platinum-based catalysts. It is rare to find electrocatalysts for methanol oxidation in acidic media because its mechanism is not fully understood yet. In this research, HNO₃ exfoliated graphite powder and iron oxide composites have been synthesized by facile, single-step hydrothermal method. This procedure replaces the long and hazardous route of synthesizing graphene oxide. These composites not only provide large surface area for electrode reactions but also utilize catalytic and electrical capabilities of graphene and iron synergistically. Samples were characterized with FTIR, XRD, and SEM analyses while electrocatalytic efficiencies were studied with cyclic voltammetry and electrochemical impedance spectroscopy. Composites have shown remarkable efficiencies for oxidation of methanol in acidic media.

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In the field of sustainable and renewable energy, developing highly active electrode materials for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) remains a significant challenge. Herein, we have used novel M-type hexaferrites, SrCo_xNi_xFe_12−2xO₁₉ materials, prepared using sol-gel auto-combustion (SGAC) route, for water splitting, in which Co and Ni elements were used as doping materials. Six different compositions of hexaferrites were prepared by varying the concentrations of Co and Ni elements. The fabricated electrode materials were then well characterized by various advanced analytical tools such as XPS, PXRD, BET, FTIR, FE-SEM, and HR-TEM to evaluate their chemical composition, oxidation state, crystallinity, porosity, functional groups and morphology. These prepared electrocatalysts were used as electrode materials for OER and HER application. The rich heterostructural interfaces and unique morphology effectively accelerate the transition of electrons and expose highly active sites for chemical reactions. Among the prepared electrocatalysts, the one with x = 1.0 (SrNi6) shows better OER activity in terms of potential and kinetic activity. ECSA and EIS studies were also conducted to support the electrochemical observations, and the results were found to be consistent with the OER and HER results. Therefore, the fabricated electrocatalysts are suitable for electrochemical applications.