Electrocatalysis最新文献

Electrocatalysts are used to promote efficient energy conversion in fuel cell, especially for the sluggish oxygen reduction reaction (ORR) at the cathode that inhibits the performance of the device. In this work, we demonstrate the use of a facile gamma radiolysis technique to synthesize carbon nanotube-supported palladium (Pd) metal particles as electrocatalysts for the ORR application. The Pd precursor concentration used in the preparation process was found to contribute greater effects on the Pd content and Pd crystallite size of the synthesized product compared to the gamma irradiation dose. The results showed that gamma radiolysis could successfully reduce Pd ions from its precursor solution as evidenced from field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) characterization. The optimal ORR electrocatalyst was prepared using 0.01-M Pd precursor and a gamma radiation dose of 50 kGy. It displays a high half-wave potential (E_1/2) of 0.84 V (vs. RHE) and superior electron transfer number (n) of 3.96, as well as a low peroxide yield of 1.8%. This impressive ORR electrocatalytic performance was also attributed to the synergistic effect of Pd metal particles with CNT. The findings showed that Pd/CNT is a promising electrocatalyst for ORR application and that gamma radiolysis provides a facile and eco-friendly approach in synthesizing electrocatalysts.

Abstract

Nickel selenide quantum dots (NiSe₂QDs) were synthesised using the aqueous colloidal method with banana peel extract (BPE) utilised as a capping agent. A gold electrode modified with the BPE-capped NiSe₂QDs was used for the determination of nevirapine. Characterisation of the BPE-NiSe₂QDs was conducted using high-resolution scanning electron microscopy (HRSEM), high-resolution transmission microscopy (HRTEM) and small-angle X-ray scattering (SAXS) which all revealed the spherical morphology of the QDs and their small sizes (˂ 10 nm). Optical properties of the BPE-NiSe₂QDs studied by ultraviolet–visible spectroscopy (UV–Vis) revealed an absorbance band at 329 nm corresponding to an energy bandgap value of 2.99 eV. The electrochemical experiments were performed using differential pulse voltammetry. The Au/BPE-NiSe₂QDs/Nafion-based electrochemical sensor showed a distinctive anodic response towards nevirapine at 0.76 V. The results obtained showed that the oxidation peak current increased linearly as the nevirapine concentrations increased in the range 0–1.21 pM (0–0.322 ng/L) with a low limit of detection (LOD) of 0.024 pM (0.0064 ng/L) and sensitivity of 5.52 µA/pM. These exceptional properties are comparable to or even better than already reported sensors for complex matrices. The electrochemical sensor demonstrated high repeatability and stability. The proposed sensor was successfully used for nevirapine detection in spiked wastewater samples with satisfactory results.

A novel peripherally tetra naphthol substituted Co(II) phthalocyanine (NCoPc) was synthesized by the reaction of naphthol linked phthalonitrile, and cobalt chloride, in the presence of catalytic amount of DMF, DBU, and K₂CO₃. The NCoPc and its composite with MWCNTs were characterized by FTIR, NMR, UV–Vis, XRD, TGA, and mass spectroscopic techniques. The NCoPc and NCoPc-MWCNTs-coated glassy carbon electrodes (GCEs) were used to electrochemically detect and quantify ortho amino phenol (oAP) oAP in aqueous solutions. Cyclic voltammetric data established a linear response between the oAP oxidation current (ipa) and its molar concentration (10–190 μM). The limit of detection (LoD) of the two modified electrodes was comparable (1.5 μM and 25 nM, respectively). The NCoPc and NCoPc-MWCNTs-GCEs (in the concentration range of 10–160 μM) were both low and comparable. The LoD values for oAP at the NCoPc-GCE and NCoPc-MWCNTs by DPV were 1.2 µM and 42 nM and CA were 10 nM and 6.5 nM, respectively. They are exhibited good electrocatalytic activity towards the oxidation of oAP, and this was aided by the improved conductivity of the composite modifiers.

Graphical Abstract

In this paper, aluminosilicate nanozeolite beta has been prepared and described using X-ray diffraction (XRD), nitrogen sorption isotherm, Fourier transform infrared (FT-IR), transmission electron micrograph (TEM), and field emission scanning electronic microscopy (FESEM) techniques; TEM image demonstrated semispherical particles with dimensions under 50 nm. The BET surface area, total pore volume, and pore diameter of it were attained to be 321 m² g⁻¹, 0.053 cm³ g⁻¹, and 1.22 nm, respectively. The modified carbon paste electrode by aluminosilicate nanozeolite beta and nickel hydroxide (Ni(OH)₂-Beta/CPE) was applied for formaldehyde (HCHO) electrocatalytic oxidation. The obtained results specify that Ni(OH)₂-Beta/CPE demonstrates worthy electrocatalytic activity for oxidation of HCHO due to mesoporous construction and the great surface area of nanozeolite. The electron-transfer coefficient, catalytic rate constant, and diffusion coefficient are found to be 0.69, 2.08 × 10⁶ cm³ mol⁻¹ s⁻¹, and 4.4 × 10⁻⁷ cm² s⁻¹, respectively. The Ni(OH)₂-Beta/CPE exhibited low background current, simplicity of surface renewal, good reproducibility, and stability and also displayed high stability up to 300 cycles and 3000 s without an important loss in the current density. This modified electrode has better poisoning tolerance capability than bare CPE for HCHO electrocatalytic oxidation and is a higher device for the long term accomplishment.

Metal sulfides have been shown to exhibit better electrical conductivity, mechanical and thermal stability, and higher electrochemical activity than their corresponding metal oxide counterparts. The one-dimensional nanoclusters and three-dimensional microspheres were assembled together by a well-designed synthetic strategy to finally form a sea urchin-like CoS₂@WS₂/NF composite electrode material. The stable chemical properties and firm physical structure remain stable before and after the catalytic reaction, and the unique structure, sea urchin-like morphology, is conducive to mass transfer and gas release during the reaction. In this nanocomposite, one-dimensional nanoclusters provide efficient electron transfer, while three-dimensional nanospheres provide strong and reliable mechanical support. When CoS₂@WS₂/NF was used as a bifunctional electrocatalyst at a current density of 10 mA cm⁻² in 1.0 M KOH aqueous solution, it exhibited overpotentials as low as 127 mV and 415 mV to drive hydrogen evolution reaction (HER) and HER, respectively. Oxygen evolution reaction (OER) is responsive while having high durability. When evaluated as a two-electrode system, it delivers a small value of 1.66 V up to 10 mA cm⁻², further demonstrating the superiority of the bifunctional water release function.

Nanocrystalline CaTiO₃ materials with controlled particle size were prepared using spray-freezing/freeze-drying approach utilizing gelatine as a structure-directing agent. The resulting materials show characteristic particle size between 19 and 60 nm. The shape of the nanocrystals changes from cube-like single crystal containing particles into less regular isometric particles. Prepared materials as identified by X-ray diffraction analysis are formed by orthorhombic perovskite with small admixture of cubic phase. The ratio of both perovskite phases is independent of the particle size or prevailing crystal shape. All prepared materials show n-semiconducting character with band gap of ca 3.6 eV. They also show photo-electrochemical activity in water oxidation in acid media if a bias greater than 400 mV with respect to the flat band potential is applied. The specific photo-electrochemical activity decreases with increasing specific surface area. This behavior is attributed to increased probability of the electron transfer at the illuminated CaTiO₃ surface facilitated by the surface states. The CaTiO₃ materials also generate significant amount of ozone upon illumination in oxygen saturated solutions. The tendency to form ozone increases with increasing particle size suggesting that the ozone formation is hindered on materials with large number of low dimensionality states (crystal edges and vertices).

Graphical Abstract

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.

Graphical Abstract

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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