Electrocatalysis最新文献

Different morphology metal nickel nanoelectrodes, such as nanospikes, layered nanosheets, layered flat particles, and hierarchical nanosheets, were synthesized on FTO glass via a hydrothermal method and utilized for glucose concentration determination in aqueous solutions under alkaline conditions. These electrodes demonstrated distinct electrochemical catalytic properties, such as surface area, mass transfer, and catalytic rate, during the glucose oxidation process. It was observed that a larger surface area can lead to a higher redox current in the absence of glucose, along with increased current noise and a prolonged response time when glucose is present. Despite having similar surface coverage, electrodes with a larger surface area can accommodate more Ni²⁺/Ni³⁺ redox couples, which generate a higher redox current in an alkaline solution. However, a poor catalytic rate for glucose can result in a low sensitivity of glucose detection. This implies that not all redox couples on the electrode surface actively participate in glucose oxidation, even when the electrodes have extensive glucose coverage and a higher density of redox couples. Moreover, a larger surface area can impede glucose diffusion, resulting in a longer response time during amperometric detection.

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The spinel CuFe₂O₄ elaborated by sol–gel route crystallizes in a tetragonal structure with a crystallite size of 444 ± 2 nm and a zeta potential of − 35 mV. The diffuse reflectance spectroscopy and photo-electrochemistry were undertaken for its characterization. The direct gap (1.55 eV) ideal for the solar energy conversion is assigned to the transition (: {Fe}_{oc}^{3+}:{t}_{2g}to {Fe}_{oc}^{4+}): ({e}_{g}) in agreement with the red color, allowing more than half of the solar spectrum to be converted into chemical energy. The narrow valence band deriving from Fe³⁺: ({t}_{2g}) orbital induces a low electron mobility (µ = 8.91 × 10⁻¹³ cm² V⁻¹ s⁻¹). The cyclic voltammetry in Na₂SO₄ (10⁻² M) exhibits low hysteresis that resembles a chemical diode. The electrical conductivity of CuFe₂O₄ is a characteristic of a non-degenerate semiconductor with activation energy (E_a) of 0.20 eV where the electron transfer occurs by low lattice polaron hopping between mixed valences Fe⁴⁺/Fe³⁺ octahedrally coordinated. The semi-logarithmic plot (logJ–E) indicates a chemical stability of CuFe₂O₄, while the photo-chronoamperometry corroborates the p-type behavior, a result confirmed by the capacitance measurement where an electron density (N_A) of 0.176 × 10²³ cm⁻³ and a flat band potential (E_fb) equal to − 0.56 V_SCE were extracted. As application and on the basis of the potential diagram, Rhodamine B (Rh B, 20 mg L⁻¹), a cationic dye, is electrostatically attracted by the electrode surface and successfully oxidized by electrocatalysis on CuFe₂O₄. The kinetics of oxidation of Rh B followed by chemical oxygen demand (COD) analysis, which gave an abatement of 56% under a current of 150 mA, an enhancement up to 70%, was reached by electro-photocatalysis under sunlight smaller than that analyzed by UV–visible spectrophotometry (88%). The color removal follows a pseudo-first-order model with a half-life t_1/2 of 57 min; a reaction mechanism by O₂^•− and ^•OH radicals is suggested.

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Methods for detecting contaminants in drinking water are crucial for protecting public health. Despite manganese (Mn) being an essential mineral for humans, Mn in high concentrations is suspected of being associated with negative cognitive and neurological effects on humans, especially on children. Current methods of detection, though reliable, are limited in the application to real-time easy-to-use, field or bench-top monitoring applications for testing drinking water. Herein, chronoamperometry (CA) is explored to quantitatively analyze manganese samples for drinking water applications. CA proved to be effective at measuring the concentration of Mn²⁺ in water samples with excellent recovery rates (97.8%) and reproducibility between electrodes. With 1-min deposition using bare gold electrodes, CA was able to obtain a detection limit of 34.3 µM. Furthermore, with a 5-min deposition using bare gold electrodes, CA was able to obtain a detection limit of 4.64 µM. This new CA method also offers a simplified cleaning method that will allow electrodes to be used continuously for differing samples or replicate tests. The cleaning procedure permits the reuse of electrodes, while simultaneously eliminating the need for special surface modifications on the electrodes. Ultimately, this cleaning procedure offers a faster and more efficient procedure than previous methods such as polishing. The CA method also demonstrated minimal interference effects when tested with varieties of water hardness, ionic strength, common electroactive species (Cu²⁺, Fe²⁺, Fe³⁺, and Cl⁻), and organic matters in aqueous environments. This CA method is easy to use, requires portable equipment, uses reagents that are easily accessible, and does not require extensive sample preparation.

The oxygen evolution reaction (OER) holds pivotal importance in sustainable energy conversion, as it forms the critical half-reaction in various electrochemical processes, including water splitting for hydrogen production and rechargeable metal-air batteries. Here, a CoFe₂O₄@Co₃O₄ nano-composite was synthesized using a facile hydrothermal process and deposited onto the surface of nickel foam through electrophoresis. Characterization using XRD, Raman spectroscopy, and XPS confirmed the successful synthesis of the composite, exhibiting characteristic peaks of both Co₃O₄ and CoFe₂O₄. The nano-composite exhibited a more amorphous phase than pure oxides, benefiting electrocatalytic activity. Scanning and transmission electron microscopy highlighted the composite’s morphological characteristics, showcasing a Co₃O₄ island distribution on the CoFe₂O₄ surface. Electrochemical evaluations revealed the superior oxygen evolution reaction (OER) performance of CoFe₂O₄@Co₃O₄, with low overpotentials, faster kinetics, and enhanced stability compared to pure oxides and the benchmark RuO₂ catalyst. A comprehensive analysis was carried out to investigate the dynamic behavior during electrocatalytic oxygen evolution reaction. This study unveils the intricate charge and electron transfer mechanisms between cobalt and iron atoms, providing insights into their collaborative role throughout the OER process.

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Corrosion has been identified as the primary mechanism causing pipeline failures, leading to significant economic losses and environmental problems. One of the effective and economical methods to prevent metal corrosion is to add corrosion inhibitors. Although environmentally friendly corrosion inhibitors are beneficial to the ecological environment, their lower corrosion inhibition efficiency compared to traditional corrosion inhibitors has limited their application. Therefore, this paper aims to develop an environmentally friendly compound corrosion inhibitor that can meet the practical industrial requirements. The corrosion inhibition effect of two complexes of cystine, namely cystine + sodium molybdate (Cys-Cys + MS) and cystine + zinc gluconate (Cys-Cys + ZG), on pipeline steel in 1 M HCl was investigated. And the synergistic corrosion inhibition mechanism of these two composite corrosion inhibitors was discussed. The results indicated that the corrosion inhibition performance of Cys-Cys + MS and Cys-Cys + ZG complexes was significantly better than that single inhibitors at higher concentration. Furthermore, it was observed that the corrosion inhibition performance of Cys-Cys + ZG was superior to that of Cys-Cys + MS. The maximum corrosion inhibition efficiency of the two compound corrosion inhibitors was achieved at the concentration of (2 + 4) mM.

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Electrocatalytic water splitting has received widespread attention due to the slow kinetics of the reaction and the complex electron transfer process, the oxygen evolution reaction (OER) occurring at the anode has become a major obstacle. The improved OER performance is attributed to the significant enhancement in accessible surface active sites and the decrease in charge transfer resistance. The exploration of efficient, cheap, and stable electrocatalysts for OER is of significant importance for energy conversion and storage. Currently, transition metal oxides (TMOs) show enormous potential as electrode materials for OER due to their low cost, redox chemistry, and high chemical stability. In this work, an impregnation method is demonstrated to synthesize Cu-based metal oxides doped with Ni (CuO, Cu_0.9Ni_0.1O, Cu_0.7Ni_0.3O, and Cu_0.5Ni_0.5O/NiO) as high-efficiency and low-energy electrocatalysts for the oxygen evolution reaction under alkaline conditions. This work combines the excellent catalytic efficiency of the transition metal with the large specific surface area and the substantial number of pores of the MOF. All materials show good overpotential values of 359, 352, 346, and 340 mV at a current density of 10 mA cm⁻². The Tafel slopes are 82.5, 47, 65, and 54 mV dec⁻¹, respectively, with very small attenuation for long-term catalytic reactions. Furthermore, the electrocatalysts showed short-term electrochemical stability for 12 h. Therefore, the present method opens a new path for the preparation of efficient and low-cost materials for application in OER.

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CO₂ reduction and fixation are one of the most interesting topics in the fields of environmental electrochemistry and electrocatalysis. Many studies on CO₂ electroreduction using various metal electrodes have been reported. However, this reaction requires a high overpotential in general, which lowers the energy conversion efficiency and prevents its practical applications to reduce CO₂ emission to the atmosphere. The use of a membrane electrode assembly (MEA) is expected to be a breakthrough for the CO₂ electroreduction. Particularly, methanation (converting CO₂ into CH₄) with MEAs incorporating Cu-based catalysts attracts special attention as a tool for carbon cycling, thanks to high faradaic efficiencies and relatively high energy conversion efficiencies. Different from Cu, Pt has long been recognized as an inactive catalyst for CO₂ reduction. Contrary to the common consensus, MEAs incorporating a Pt-based electrocatalyst were found very recently to be as active as Cu-based catalysts toward methanation under specific reaction conditions. The high activity of Pt arises from a reaction mechanism different from that for Cu; most likely the Langmuir–Hinshelwood mechanism for Pt and the Eley–Rideal mechanism for Cu. This mini-review discusses CO₂ electrochemical methanation using MEAs as a potential method for carbon capture. The CO₂ reduction to CH₄ using a H₂-CO₂ fuel cell is also presented.

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In this study, we have investigated the synthesis of supported iridium oxide (IrO_x) nanoparticles (NPs) through hydrolysis in a surfactant-free aqueous bath as a possible route for the large-scale production of highly active electrocatalyst for oxygen evolution reaction (OER) in acidic water electrolyzers. The process involves (i) formation of Ir-hydroxides complex from an Ir precursor in basic media followed by (ii) protonation in acidic media to form colloidal hydrated IrO_x NPs and (iii) conversion and deposition of IrO_x NPs on the surface of carbon or TiN support by probe sonication. The IrO_x NPs produced through hydrolysis route form highly stable colloidal solution. Since it is essential to precipitate the catalyst NPs from the colloidal solution for their use in water electrolyzer electrode development, here, we investigate the optimal reaction conditions, e.g., pH, temperature, time, and presence of support, for efficient synthesis of the catalyst NPs. The reaction intermediates formed at different reaction steps are explored to get insights into the chemistry of the process. Under the optimal synthesis conditions, 100% precipitation of IrO_x NPs was achieved. Further, the precipitated TiN supported IrO_x NPs exhibited high OER activity, superior to that of the commercial benchmark IrO₂ electrocatalyst. The study provides a scalable synthesis route for highly active, low Ir-content OER electrocatalysts for acidic water electrolyzers.

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In this work, the CeO₂ nanoparticles were dispersed onto the surface of graphene oxide (GO), followed by electrodeposition of Pt–Pd alloy nanoparticles on the CeO₂ surface to fabricate Pt–Pd@CeO₂/graphene oxide composites (Pt–Pd@CeO₂/GO). Morphological investigation was conducted using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The results of morphological characterization revealed that CeO₂ nanoparticles acted as cores, while Pt–Pd alloy nanoparticles formed shells. The electrocatalytic oxidation performance of Pt–Pd@CeO₂/GO composites for methanol electro-oxidation reaction (MOR) was systematically investigated. The mass activity for MOR on Pt₁Pd_1.3@CeO₂/GO electrocatalyst was 1128 mA·mg_Pt+Pd⁻¹, which was 5.0-fold higher than that of Pt/C catalysts. The synergistic effect between Pt and Pd, along with the active oxygen-containing species of CeO₂ effectively enhanced catalytic activity. This work presents a novel approach to developing catalysts with high catalytic performance for MOR.

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Metal-organic cobalt hydroxide emerges as a cost-effective electrocatalyst for the oxygen evolution reaction (OER) in energy conversion. However, the limited active sites and poor conductivity hinder their large-scale application. This study employed salicylate as a bridging ligand to synthesize iron-incorporated metal-organic cobalt hydroxide. The influence of Fe intercalation on Co(OH)(Hsal) (where Hsal denotes o-HOC₆H₄COO⁻) was investigated using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Fe_0.2Co_0.8(OH)(Hsal) demonstrates remarkable electrocatalytic activity, displaying an OER overpotential of 298 mV at 10 mA cm⁻² and a Tafel slope of 57.46 mV dec⁻¹. This enhancement can be attributed to improved charge transfer kinetics and increased active sites. This work highlights the crucial role of Fe in improving the efficiency of Co-based oxygen-evolving catalysts (OECs) and its potential for boosting efficient hydrogen generation in alkaline environments.

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