Electrocatalysis最新文献

Metal–organic frame materials (MOFs) create ordered spatial structures through organic bridges and metal ion centers. This microstructure can effectively disperse the active centers. In this work, CuCo-MOF was firstly prepared by hydrothermal method and then physically mixed with MoS₂. The prepared materials were applied to study the catalytic performance for oxygen evolution reaction (OER). The results show that the overpotential and Tafel slope of CuCo-MOF/MoS₂ are 336 mV and 75 mV dec⁻¹. The addition of MoS₂ can effectively reduce the stacking of MOFs and increase the effective contact area with the reactants and promote charge/mass transport as well as enhance the catalytic activity. In addition, MoS₂ has strong viscosity, and when it is mixed with MOF, the stability of the composite can be improved. The good OER performance of CuCo-MOF/MoS₂ provides a reference for the exploration of a novel OER catalyst.

We have used density functional theory calculations to study the sequential adsorption of hydrogen on Pd and Pt atomic site catalysts such as single-atom alloy catalysts (SAAC), single-atom catalysts (SAC), and single cluster catalysts (SCC) on Au(111). The results show that Pd systems tend to have near-zero free energy of hydrogen adsorption ((Delta {G}_{{mathrm{H}}_{mathrm{ads}}}approx 0)) under various coverage conditions of adsorbed hydrogen. In the case of Pt systems, (Delta {G}_{{mathrm{H}}_{mathrm{ads}}}approx 0) only at high coverage conditions of adsorbed hydrogen. Such differences come from the preference of hydrogen for high-coordination and low-coordination sites on Pd and Pt, respectively. The low coordination of hydrogen results in multiple adsorption sites with (Delta {G}_{{mathrm{H}}_{mathrm{ads}}}approx 0) in SCC of Pt/Au. These results can help to understand the different catalytic properties of Pd/Au and Pt/Au.

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To effectively degrade antibiotics, a series of MnO₂ modified electrodes were prepared by using a thermal decomposition method in this study. The corrosion resistance of the coated electrodes was evaluated by characterizing the microscopic morphology of the electrodes using scanning electron microscopy (SEM). Moreover, electrochemical tests, including cyclic voltammetry (CV) curves, linear sweep voltammetry (LSV) curves, as well as alternating-current (AC) electrochemical impedance spectroscopy (EIS), were applied to study the electrocatalytic ability of the electrode for the degradation of doxycycline hydrochloride in simulated wastewater. Based on the findings, the MnO₂/CuO-mesoporous silica (SBA)-15 electrode displayed a long lifetime and excellent catalytic performance. The peroxynitrite (PMS) was further combined with above electrodes to construct an electrocatalytic oxidation (EC) system for the removing of doxycycline hydrochloride from wastewater. Under optimized conditions (current density of 30 mA/cm², initial pH of 5, PMS dosing of 350 mg/L), the MnO₂/CuO-SBA-15/PMS system can remove 79.44% doxycycline hydrochloride (initial concentration of 20 mg/L) after 180 min of electrolysis, 24.71% higher than that in the MnO₂/PMS system.

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Pt₃Fe(111), Pt₃Fe(775) = 7(111)–(111), and Pt₃Fe(544) = 9(111)–(100) electrodes show the highest activity in the low-index planes, n(111)–(111), and n(111)–(100) series of Pt₃Fe, respectively. The surfaces of these electrodes were modified with hydrophobic species such as THA⁺, melamine, and ionic liquid ([MTBD][beti]), and the effects on the oxygen reduction reaction (ORR) were studied. All the hydrophobic species improved the ORR activity on all the electrodes examined. The ORR activity of Pt₃Fe(111) in 0.1 M HClO₄ containing 0.1 μM melamine was 2.1 times higher than that of Pt₃Fe(111) without melamine, giving 39 times higher activity than that of bare Pt(111). The durability was improved on all the electrodes examined in melamine-containing solution.

Regardless of great efforts, the development of novel low cost electrocatalysts with high electrocatalytic activity for the oxygen reduction reaction (ORR) remains a real challenge. This is a setback for the mass commercialization of one of the eco-friendliest alternative power sources: fuel cells (FCs). Thus, this work describes the preparation of four composites based on the 48-tungsto-8-phosphate polyanion salt K₂₈Li₅[H₇P₈W₄₈O₁₈₄]·92H₂O (KLi-P₈W₄₈) immobilized on four distinct carbon materials, namely graphene flakes (GF), single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT), and N-doped multi-walled carbon nanotubes (N-MWCNT), and their application as ORR electrocatalysts. In alkaline medium, all composites exhibited electrocatalytic activity with onset potentials between 0.71 and 0.94 V vs. RHE, while P₈W₄₈@N-MWCNT presented superior current density (−3.3 mA cm⁻²). A mixed electron process of 2- and 4-electrons is observed for all the composites, supporting the results of % H₂O₂ production. Additionally, low Tafel slopes were obtained (43–82 mV dec^–1) for all composites. The electrocatalysts also showed excellent tolerance to methanol, with current retentions of 91–93%, and good electrochemical stability with current retentions between 67 and 82% after 36,000 s.

The inhibitory performance of quince extract (QE) on the corrosion and electrochemical properties of low-carbon steel in 1 molar hydrochloric acid was studied by electrochemical methods and weight loss measurement. The chemical compounds contained in quince that offer substantial corrosion inhibition impacts (e.g., amino acids and flavonoids) were examined by Fourier-transform infrared spectroscopy and ultraviolet. Polarization tests and electrochemical impedance spectroscopy results showed that increasing the concentration of the extract in the range of 200–1200 ppm increased its inhibition efficiency. The highest inhibition efficiency of the extract based on polarization and EIS results was respectively 95% and 93.0%, both observed at a concentration of 1200 ppm. Based on the results, quince extract was considered as a mixed-type corrosion inhibitor. Scanning electron microscopy and atomic force microscopy of the surface of steel specimens immersed in 1 M HCl without and with 200–1200 ppm of the inhibitor showed the effectiveness of quince extract in preventing corrosion.

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For the hydrogen oxidation reaction (HOR), platinum group metal (PGM) catalysts are still the norm, and their large initial catalytic activity is counterbalanced by their uncertain durability in alkaline environments: harsh degradations proceed, like detachment and agglomeration of metallic nanoparticles from the carbon support, as witnessed from dedicated accelerated stress tests (AST). Herein, a strategy to increase such catalysts’ durability is provided, using carbon layers surrounding the Pd-based carbon-supported nanoparticles. The robustness of such catalysts, baring 0.5- or 0.7-nm-thick carbon cap over the Pd nanoparticles, is evaluated from AST combined with several pre/post-test characterization techniques: identical location transmission electron microscopy (IL-TEM), ex situ X-ray photoelectron spectroscopy (XPS) and ex situ inductively coupled plasma mass spectrometry (ICP-MS). The carbon layer protection limits the Pd-based nanoparticles’ agglomeration, detachment, and metal leaching, improving long-term catalyst durability in HOR-like operation. Thicker carbon layers surrounding the Pd nanoparticles lead to higher materials durability and lower degradation rate (larger performance stability) upon AST, compared to thinner carbon layers. In addition, the carbon-capped catalysts enable to maintain better the required Pd/PdO state of the surface that is essential for fast HOR, resulting in superior intrinsic HOR activity versus unprotected Pd/C. Overall, this work demonstrates that the activity-durability relationship can be tuned for carbon-capped catalysts.

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The hydrogen evolution reaction on electroless Ni–P alloy coatings on steel substrate with decreasing content of P from 8.2 to 3.4 wt% is investigated in 1 M KOH. The lowering of the P content in the alloy coating is achieved by decreasing the concentration of sodium hypophosphite in the solution for electroless deposition. Electrochemical investigations in combination with electron microscopy and radiographic analyses (SEM, EDS, XRD, TEM) reveal that the electrocatalytic activity of Ni–P coatings in regard to the hydrogen evolution reaction depends on the complex action of structure (morphology, phase composition), P content, and thickness. A change in any of these characteristics may lead to a change in other properties such as ability of the electrodes to adsorb and absorb hydrogen. Correct assessment of the contribution of individual factors is not possible due to the fact that the conditions for obtaining the coatings cannot be set in such a way as to lead to a change in only one of the factors.

Binder-free nickel–cobalt phosphate (NiCoPO) micro flakes are evenly grown on the nickel foam (NF) by a simple hydrothermal method, which can act as a highly efficient bifunctional electrocatalyst (NiCoPO/NF) for both oxygen evolution reaction (OER) and urea oxidation reaction (UOR). NiCoPO/NF presents the relatively prominent OER and UOR activities with ultralow potentials of 1.51 V and 1.34 V (vs. reversible hydrogen electrode) to reach the current density of 100 mA cm⁻², respectively. The outstanding UOR and OER performance of NiCoPO/NF might be attributed to the fact that the successful incorporation of oxygen atoms into Ni/Co phosphate is beneficial for the oxidation of metal atoms at high overpotential. In addition, NF can improve the electrical conductivity to accelerate the electron transfer from the electrode to the catalyst. Additionally, in the alkaline solution (1 M KOH), NiCoPO/NF shows excellent durability and stability after the consecutive OER and UOR tests for 48 h. The design of NiCoPO/NF would pave the way to construct more efficient bifunctional electrodes for electrocatalytic water splitting with or without urea in alkaline solution, which provides a novel technological platform for the conversion of human waste into the sustainable energy.

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Tenofovir (TNF), a nucleotide analogue of adenosine 5′-monophosphate, is the first-line treatment for chronic HIV/hepatitis B coinfection. There is a need to explore highly sensitive, rapid, and cost-effective quality control techniques to detect the drug. Nickel sulphide @ poly(acrylic acid) coated multi-walled carbon nanotubes (NiS@PAA-MWCNT) composite was synthesized using the one-step solvothermal method. The composite was characterized by UV-vis spectroscopy, Fourier transforms infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy. Morphological analysis showed polydispersed NiS on the surface of the poly(acrylic acid) coated multi-walled carbon nanotube (MWCNT). Tenofovir was electrochemically detected in human urine by differential pulse voltammetry (DPV) using the NiS@PAA-MWCNT modified glassy carbon electrode. The linear range was found to be from 20 to 80 µM with a limit of detection of 5.83 × 10⁻¹² M and 5.12 × 10⁻¹² M in phosphate buffer and human urine, respectively. The practical applicability of the modified electrode was evaluated in human urine and in the presence of different interfering agents. The electrode demonstrated good reproducibility, selectivity, and sensitivity. Thus, NiS@PAA-MWCNT nanocomposite can be used in electrochemical sensors for quality control purposes.

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