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In this scientific work, a precipitation method is followed for the synthesis of copper oxide (CuO), cobalt oxide (Co3O4) and copper cobaltite (CuCo2O4) and the viability of using these materials as electrode modifiers has been studied. A sensitive electrochemical sensor for the determination of hydroxylamine has been introduced. The morphology and physical properties of the as synthesized materials were characterized with several characterization tools. It is found that the morphology and size of CuO, Co3O4 and CuCo2O4 are nanoflakes (300–350 nm), nanoplatelet (75–100 nm) and nanobricks (20–45 nm), respectively. In addition, CuO, Co3O4 and CuCo2O4 oxidize hydroxylamine at 0.57 V, 0.53 V and 0.44 V, respectively. Electrocatalytic oxidation current of hydroxylamine was proportional to the concentration of hydroxylamine in the range 0.075 to 8.25 mM. Also, under optimized condition, limit of detection and sensitivity in the DPV measurement are 0.65 μM ± 0.05 μM and 13.1 μA cm−2 mM−1, respectively. Hence, the proposed sensor is highly sensitive, selective, simple, precise and stable for hydroxylamine detection in the real water samples. [ABSTRACT FROM AUTHOR]

In this work, a hard‐template‐based nano‐replication process is employed to prepare mesoporous MnO2 materials. We adopted four silica materials, namely, SBA‐15, KIT‐6, MCM‐41, and MCM‐48 as templates to prepare MnO2 materials by using a nanocasting route. The structural characteristics of the resultant MnO2 materials were thoroughly investigated by using XRD, BET, FESEM, HR‐TEM, XPS, and Raman techniques. All studies confirmed the replication of porous MnO2 nanostructures from silica supports in β‐crystallographic form. By employing X‐ray absorption near‐edge structure (XANES) and extended X‐ray absorption fine structure (EXAFS), we identified the existence of Mn and oxygen vacancies in the developed MnO2 material. The hydrodynamic linear sweep voltammetric technique was employed to demonstrate the efficient oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) activity of the catalyst in 0.1 M KOH solution. The KIT‐6‐derived MnO2 nanostructure displayed equal activity to the benchmark catalyst RuO2. This work lays a foundation to prepare and employ ordered mesoporous MnO2 materials as OER/ORR catalysts, which have potential applications in electrochemical energy conversion and storage devices. Bifunctional catalysts: Mesoporous MnO2 materials are obtained from a hard‐template‐based nanocasting method. SBA‐15, KIT‐6, MCM‐41, and MCM‐48 are selected as (2D and 3D) templates. The replication of porous MnO2 nanostructures from silica supports yields the β‐crystallographic form. X‐ray absorption studies identify the existence of Mn and oxygen vacancies in the materials. Electrochemical studies demonstrate efficient oxygen evolution and oxygen reduction reaction activity of the resultant materials. 3D MnO2 displays an activity comparable to the benchmark RuO2 catalyst. [ABSTRACT FROM AUTHOR]

The chemical state and formation mechanism of Pt-Ru nanoparticles (NPs) synthesized by using ethylene glycol (EG) as a reducing agent and their stability have been examined by in situ X-ray absorption spectroscopy (XAS) at the Pt LIII and Ru K edges. It appears that the reduction of Pt(IV) and Ru(III) precursor salts by EG is not a straightforward reaction but involves different intermediate steps. The pH control of the reaction mixture containing Pt(IV) and Ru(III) precursor salts in EG to 11 led to the reduction of Pt(IV) to Pt(II) corresponding to [PtCl4](2-) whereas Ru(III)Cl3 is changed to the [Ru(OH)6](3-) species. Refluxing the mixture containing [PtCl4](2-) and [Ru(OH)6](3-) species at 160 degrees C for 0.5 h produces Pt-Ru NPs as indicated by the presence of Pt and Ru in the first coordination shell of the respective metals. No change in XAS structural parameters is found when the reaction time is further increased, indicating that the Pt-Ru NPs formed are extremely stable and less prone to aggregation. XAS structural parameters suggest a Pt-rich core and a Ru-rich shell structure for the final Pt-Ru NPs. Due to the inherent advantages of the EG reduction method, the atomic distribution and alloying extent of Pt and Ru in the Pt-Ru NPs synthesized by the EG method are higher than those of the Pt-Ru/C NPs synthesized by a modified Watanabe method.