Electrocatalysis最新文献

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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The growing interest in energy demand became an important issue for several sectors like industry and transportation. Recently, fuel cells generated a new solution for global energy deficiency. Therefore, we developed a new catalyst for fuel cell applications that included nickel oxide nanoflower with polyaniline to enhance the electrooxidation of ethanol. The structure of the modified electrode was characterized by X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR). At the same time, surface morphology and structural thermal stability were utilized by Scanning electron spectroscopy (SEM) and Thermal gravimetric analysis (TGA), respectively. Otherwise, ethanol electrooxidation was studied by several electrochemistry techniques like cyclic voltammetry (CVs) and chronoamperometry (CA). The activity of the electrocatalyst toward ethanol conversion reached 32 mA cm⁻² at a potential of 0.46 V (vs. Ag/AgCl). The effect of changing the thickness of the conducting polymer was studied to find out the optimum catalysis condition. Several chemical kinetics were calculated, like diffusion coefficient (D), Tafel slope, and transfer coefficient. The long-term stability of the modified electrode for 240 min. Whereas the anodic current decreased by 15% after continuous oxidation of ethanol in an alkaline medium.

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Utilizing the density functional theory (DFT) method, we investigated the catalytic activity of N-doped graphene quantum dots (NGQDs) with nitrogen (N) atoms strategically doped at various active sites on the surface. We focused on exploring their efficiency in the 2e⁻ and 4e⁻ reduction pathways for oxygen reduction reaction (ORR). By introducing N-doping at the central benzene ring of carbon-based materials, we observed the formation of localized π-orbitals, significantly enhancing their electrocatalytic activity. In comparison to other reported catalysts, our N-doped GQD metal-free electrocatalyst displayed remarkable adsorption capability. Furthermore, we introduced the hydroxyl group (OH) into the functionalized N-doped GQDs, which further improved electrocatalytic performance. This enhancement was attributed to the decreased HOMO–LUMO energy gap and increased chemical reactivity. The calculated free energy (ΔG) values for each elementary reaction step in the 4e⁻ reduction pathway were highly favorable and indicated the feasibility of the process. Our findings indicate that N-doped GQDs exhibit exceptional activity for the ORR, positioning them as promising carbon-based metal-free electrocatalysts. Consequently, they hold significant potential as an alternative to noble metal-based catalysts in proton exchange membrane fuel cells (PEMFCs) and metal-air batteries.

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Ammonia (NH₃) is one of the most used chemicals. Industrially, ammonia is produced by hydrogenation of N₂ through the Haber–Bosch process, a process in which enormous amounts of CO₂ are released and requires a huge energy consumption (~ 2% of the total global energy). Therefore, it is of paramount importance to explore more sustainable and environmentally friendly routes to produce NH₃. The electrochemical nitrogen reduction reaction (NRR) to ammonia represents a promising alternative that is receiving great attention but still needs to be significantly improved to be economically competitive. In this work, the NRR is studied on Pt–Rh nanoparticle–based electrodes. Carbon-supported Pt–Rh nanoparticles (2–4 nm) with different Pt:Rh atomic compositions were synthesized and subsequently airbrushed onto carbon Toray paper to fabricate electrodes. The electrochemical NRR experiments were performed in a H-cell in 0.1 M Na₂SO₄ solution. The results obtained show interesting faradaic efficiencies (FE) towards NH₃ which range between 5 and 23% and reasonable and reliable NH₃ yield values of about 4.5 µg h⁻¹ mg_cat⁻¹, depending on the atomic composition of the electrocatalysts and the metal loading. The electrodes also showed good stability and recyclability (constant FE and NH₃ yield in five consecutive experiments).

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Pt–Rh nanoparticle–based electrodes were employed for the NRR to NH₃ in 0.1 M Na₂SO₄. Interesting FE towards NH₃ and reasonable and reliable NH₃ yield values were observed depending on atomic composition and metal loading. Good stability and recyclability (constant FE and NH₃ yield in five consecutive experiments) were also observed.

Herein, we present a novel blended solid polymer electrolyte system composed of polyvinylidene fluoride-co-hexafluoropropylene (PVDF-co-HFP) and polymethyl methacrylate (PMMA) with the addition of phenothiazine (PZ) as an additive and iodide/triiodide (I^-/I₃^-) as a redox couple in nanocrystalline TiO₂ dye-sensitized solar cells (DSSCs). The characterization of the blended solid polymer electrolyte was conducted using techniques such as XRD, FTIR, SEM, and current-voltage (I-V) measurements. Our analyses revealed a decrease in the degree of crystallinity in PVDF-co-HFP/PMMA-based blended solid polymer electrolytes due to the incorporation of PZ, as observed through XRD, FTIR, and SEM. The electrical conductivity of the optimized solid polymer electrolyte film was determined using complex impedance spectroscopy, showing a maximum ionic conductivity value of 3.2 × 10^-7 Scm^-1 at ambient temperature (298 K). DSSCs based on nanocrystalline TiO₂ were fabricated, and the cell parameters, including short-circuit current density (J_sc), open-circuit voltage (V_oc), fill factor (ff), and photovoltaic energy conversion efficiency (η), were evaluated. The DSSC fabricated with the polymer electrolyte exhibited values of 9.3 mA/cm², 800 mV, 0.56, and 5.2% for J_sc, Voc, ff, and η, respectively, under 80 mW/cm² at AM 1.5 simulated solar irradiation.

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The determination of complex structure helps to explore its reaction mechanism and provides design strategies for guiding synthesis of high-performance hydrogen evolution reaction (HER) electrocatalysts. A new mononuclear Ni(II) complex, [Ni(p-MOPhH₂IDC)₂(H₂O)₂], was synthesized by the reaction of p-MOPhH₃IDC (2-(4-methoxyphenyl)-1 H-imidazole-4,5-dicarboxylic acid) and Ni(NO₃)₂·6H₂O under solvothermal conditions and characterized by single-crystal X-ray diffraction, elemental analysis, IR and UV-vis spectroscopy. The structure analysis revealed that the nickel center was six-coordinated octahedron coordination geometry. The electrochemical properties of the Ni(II) complex-doped carbon paste electrode (Ni-CPE) were investigated by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) in 0.5 M H₂SO₄ electrolyte. The HER measurements show that the η₁₀^298K (overpotential, 10 mA cm^–2) of the Ni-CPE was positively shifted by 265 mv compared with the bare-CPE (without complex). The Tafel slope of the Ni-CPE was 187 mV dec^− 1. These indicated that the Ni-CPE was effective for HER electrocatalytic reaction. In addition, the electrochemical sensing performances of the Ni-CPE towards H₂O₂ were found to have a linear response from 0.5 µM to 4.0 mM with a detection limit of 0.036 µM. The above studies prove that the Ni(II) complex can be used as an effective bi-functional molecular electrocatalyst for HER and H₂O₂ sensing, and provide a new approach for designing efficient, non-precious metal electrochemical catalysts.

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A new mononuclear Ni(II) complex, [Ni(p-MOPhH₂IDC)₂(H₂O)₂], was synthesized under solvothermal conditions. The electrochemical properties of the Ni(II) complex-doped carbon paste electrode (Ni-CPE) were investigated. In the HER study, the Ni-CPE has more positive overpotentials (η₁₀^293K), smaller Tafel slopes and lower activation energies in the HER process compared to the bare-CPE, demonstrating that the Ni-CPE has effective electrocatalytic hydrogen evolution activity. Moreover, electrochemical sensing performance shows that Ni-CPE has good detection ability for H₂O₂ and exhibit good stability and anti-interference properties. Therefore, the Ni-CPE can be used as an effective bifunctional electrocatalyst.