XPS and voltammetric studies on Ni1−xCuxCo2O4 spinel oxide electrodes

Hydrothermal synthesis of ZnZrO2/chitosan (ZnZrO2/CS) nanocomposite for highly sensitive detection of glucose and hydrogen peroxide

In this work, pure ZnZrO₂ and chitosan supported (ZnZrO₂/CS) nanocomposite have been synthesized at low coast by hydrothermal method. FT-IR, Micro Raman, PXRD, HR-SEM-EDAX, HR-TEM, AFM, BET and XPS were used to analyze the structural and morphological properties of the fabricated nanocomposites. The fabricated ZnZrO₂ and ZnZrO₂/CS nanocomposites were measured for their electrocatalytic activity towards glucose and hydrogen peroxide determinations. The ZnZrO₂/CS sensor exhibited wide detection range (5 μM to 5.85 mM), high sensitivity (6.78 μA mM^-1 cm^-2), LOD (2.31 μM), and long-term stability for glucose detection in alkaline solution. Also, as a multifunctional electrochemical sensor, ZnZrO₂/CS sensor exhibits excellent sensing ability towards hydrogen peroxide, with a wide dynamic range (20 μM to 6.85 mM), a high sensitivity (2.22 μA mM^-1 cm^-2), and a LOD (2.08 μM) (S/N = 3). The electrochemical measurement shows that the ZnZrO₂/CS sensor has excellent catalytic activity and a much LOD than ZnZrO₂. The modified electrode showed excellent anti interference nature. Furthermore, this ZnZrO₂/CS electrode was used to detection of glucose and H₂O₂ in human blood serum and HeLa cells respectively.

Treatment of shale gas produced water by magnetic CuFe2O4/TNTs hybrid heterogeneous catalyzed ozone: Efficiency and mechanisms

Magnetic spinel ferrite (CuFe₂O₄) has been applied to catalyze ozone for treating the practical shale gas produced water (PW) in our previous study. In this work, CuFe₂O₄/titanium nanotubes (TNTs) catalyst was successfully prepared by an impregnation-calcination method. Characterization results revealed that the crystal form of CuFe₂O₄ was bound to the surface of TNTs, the particle size is much smaller than the pure CuFe₂O₄ crystal particle, which could weaken the influence of the internal diffusion process on its catalytic efficiency. The experimental results showed that the removal ratio of COD_Cr in the CuFe₂O₄/TNTs/O₃ system was approximately 14% higher than that of the CuFe₂O₄/O₃ system. The dissolution of metal elements decreased to one-third that of the CuFe₂O₄/O₃ system. The inhibition ratio of PW on the growth of E. coli K12 decreased 68% after the CuFe₂O₄/TNTs catalytic oxidation process. Experimental results of complete capture experiments illustrated that the yield of HO• of the CuFe₂O₄/TNTs/O₃ system was 10-19% higher than that of the CuFe₂O₄/O₃ system. The elemental valence analysis revealed that the transition of Cu(II)-Cu(III) and Fe(II)-Fe(III) coexisted in the catalytic system. Besides, the surface hydroxyl groups promoted the electron transfer process and enhanced the ozone adsorption affinity. The proposed catalytic mechanisms of the CuFe₂O₄/TNTs/O₃ system were proposed via the above analysis.

Growth and properties of spinel structure Zn1.8Co0.2TiO4 single crystals by the optical floating zone method

The spinel structure Zn_1.8Co_0.2TiO₄ single crystals with 5 mm diameter and 30 mm length were successfully grown by an optical floating zone method. The as-grown crystals were characterized by X-ray diffraction (XRD), Raman and X-ray photoelectron spectroscopy (XPS). Some Zn²⁺ ions at tetrahedral and octahedral sites should be replaced by doped transition metal Co²⁺ ions. The temperature-dependent Raman spectra of spinel Zn_1.8Co_0.2TiO₄ crystals were also described. The optical phonon behaviors of Zn_1.8Co_0.2TiO₄ are stable within the temperature range. The magnetic properties of Zn_1.8Co_0.2TiO₄ were investigated by using Physical Property Measurement System.

The spinel structure Zn_1.8Co_0.2TiO₄ single crystals with 5 mm diameter and 30 mm length were successfully grown by an optical floating zone method.

Nanoforest of hierarchical core/shell CuO@NiCo2O4 nanowire heterostructure arrays on nickel foam for high-performance supercapacitors

Nickel foam-supported hierarchical core/shell CuO@NiCo₂O₄ nanowire heterostructure arrays with excellent supercapacitive performance are reported.

Synthesis of hierarchical ZnO/ZnFe2O4 nanoforests with enhanced gas-sensing performance toward ethanol

Hierarchical ZnO/ZnFe₂O₄ nanoforests with ZnO backbones and ZnFe₂O₄ nanosheets were successfully prepared by a facile two-step process.

Surface synergistic effect in well-dispersed Cu/MgO catalysts for highly efficient vapor-phase hydrogenation of carbonyl compounds

Well-dispersed Cu/MgO catalysts exhibited excellent catalytic performance in vapor-phase hydrogenation of carbonyl compounds based on surface synergistic effect.

Preparation and Characterization of Copper-Doped Cobalt Oxide Electrodes

Cobalt oxide (Co3O4) and copper-doped cobalt oxide (CuxCo(3-x)O4) films have been prepared onto titanium support by the thermal decomposition method. The electrodes have been characterized by different techniques such as cyclic voltammetry, scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy (XPS). The effect on the electrochemical and crystallographic properties and surface morphology of the amount of copper in the oxide layer has been analyzed. The XPS spectra correspond to a characteristic monophasic Cu-Co spinel oxides when x is below 1. However, when the copper content exceeds that for the stoichiometric CuCo2O4 spinel, a new CuO phase segregates at the surface. The analysis of the surface cation distribution indicates that Cu(II) has preference for octahedral sites.

Unsteady-State Direct Partial Oxidation of Methane to Synthesis Gas in a Fixed-Bed Reactor Using AFeO3 (A = La, Nd, Eu) Perovskite-Type Oxides as Oxygen Storage

Direct partial oxidation of methane to synthesis gas on AFeO(3) (A = La, Nd, Eu) oxides by a novel sequential redox cyclic reaction in the absence of gaseous oxygen was investigated over a fixed-bed reactor. These oxides were prepared by the sol-gel method and characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques. XRD analysis showed that all AFeO(3) (A = La, Nd, Eu) oxides, calcined at 1173 K, are single-phase perovskites. The CH(4)-TPSR/MS and continuous reaction experiments indicated that the AFeO(3) (A = La, Nd, Eu) oxides provide mostly oxygen species, as the sole oxidant originated from lattice oxygen instead of gaseous oxygen, which can oxidize CH(4) to synthesis gas with high selectivity in the absence of gaseous oxygen. In terms of material economics and the amount of oxygen species for synthesis gas formation, the LaFeO(3) sample exhibits the best performance among these tested AFeO(3) oxides for synthesis gas production. The pulse experiments at different temperatures showed that the rate of oxygen migration during the CH(4) reaction with LaFeO(3) is strongly affected by the reaction temperature, and increases with rising temperature, which is favorable to much more CH(4) selective oxidation at high temperature. The two types of oxygen species are identified by experiments of continuous reactions and pulses, and confirmed by XPS. Methane can be converted selectively to synthesis gas by consumption of lattice oxygen, and general carbonaceous deposits on the catalyst surface do not occur under the appropriate reaction conditions by sequential redox cycles. The performance of selective oxidation of CH(4) to synthesis gas can be recovered by reoxidation using gaseous molecular oxygen; the LaFeO(3) oxide maintains relatively high catalytic activity and structural stability in redox atmospheres.