Electrocatalysis最新文献

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.

The present work involves the design and validation of an electrochemical sensor for precise and selective sensing of nicotinamide adenine dinucleotide (NADH). The designed electrochemical sensor consists of TCNQ and Pd-Co@NC nanocomposite–modified electrodes (TCNQ-Pd-Co@NC/CPE). The designed electrode was validated by cyclic voltammetry, amperometry, and electrochemical impedance spectroscopy (EIS). The results revealed potent electrocatalytic activity towards NADH oxidation and sensing. Cyclic voltammetry revealed the superior capability of TCNQ-Pd-Co@NC-based carbon paste electrode in electron transfer than TCNQ-Co@NC/CPE and TCNQ/CPE, validating better conductivity of TCNQ-Pd-Co@NC/CPE for NADH sensing. Amperometry study provided a wide linear range of 10 to 250 µM for NADH detection with a low detection limit (LOD) of 5.17 µM and a sensitivity of 21.5 µA mM. EIS study revealed the lowest R_ct value of 12.5 × 10² for TCNQ-Pd-Co@NC/CPE compared to TCNQ-Co@NC/CPE and TCNQ/CPE, demonstrating high electron transfer capability and thus sensitivity towards NADH. Besides this, the modified TCNQ-Pd-Co@NC-based carbon paste electrodes offered exceptional selectivity, reproducibility, and stability over time. Therefore, designed TCNQ-Pd-Co@NC nanocomposite–based carbon paste electrodes can be efficiently used for precise and selective NADH sensing.

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The electronic coupling effect by interfacial engineering between noble metal and transition metal tungstates is considered an effective strategy for improving electrocatalytic activity. Herein we introduced a new hybrid electrocatalyst consisting of Pd nanoparticle supported on NiWO₄ nanocrystals modified carbon for efficient alcohol electro-oxidation reaction. Bimetallic oxide resulted as an efficient interface modulator for Pd over mono metallic oxides. The synthesised catalyst, Pd over nickel tungstate modified Vulcan, exhibited well-dispersed homogeneous Pd particles. The catalytic effectiveness for the electro-oxidation of methanol and ethanol was found to be enhanced around ten times (1202.48 mA/mg_Pd) and six times (1508.24 mA/mg_Pd), respectively compared to Pd deposited over C catalyst. The enhanced electrochemical property owing to electronic modification and improved surface area, by the strong coupling of Pd with nickel tungstate and carbon support conferred excellent catalytic performance for the synthesised catalyst.

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