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Comparative study of catalytic activities among transition metal-doped IrO₂ nanoparticles.

ABSTRACT: Catalytic activities of transition metal-doped IrO₂ nanoparticles (TM-IrO₂ NPs; TM?=?Cr, Mn, Fe, Co, or Ni) are compared for various oxidation reactions such as electrochemical oxygen evolution reaction (OER), gas-phase photo-oxidation of thiol function group, and CO oxidative conversion. Here, we discovered a series of TM-IrO₂ catalysts have a common activity trend for these oxidation reactions, and their activities are closely related with modified electronic states of IrO₂, strongly affected by the types of the transition metal across the periodic table. For all oxidation reactions, Cr- and Mn-IrO₂ achieved the highest oxidation catalytic activity, and sequentially decreased activities were obtained with Fe, Co, and Ni doped IrO₂. For instance, the highest OER activity was achieved by Cr or Mn doping exhibiting the smallest overpotential ??=?275~230?mV at 10?mA/cm², while Ni-IrO₂ showed rather larger overpotential (??=?347?mV) even compared with non-doped IrO₂ (??=?314?mV). Scanning transmission X-ray microscopy and high-resolution photoemission spectra of TM-IrO₂ indicated dopant metals modified the Ir-O interaction and thus increasing oxygen vacancy defects in IrO₂. Strongly positive correlation was observed between the catalytic activities and vacancy states. The amount of defect related signals was observed the most for Cr- or Mn-IrO₂, less so for Fe- or Co-IrO₂, and unnoted for Ni-IrO₂ compared with bare IrO₂. Based on these catalytic activities and surface spectroscopic analysis results, vacancy defects induced by doping in TM-IrO₂ NPs are proposed to contribute to enhance the oxidation activities.

SUBMITTER: Lee H

PROVIDER: S-EPMC6233218 | biostudies-literature | 2018 Nov

REPOSITORIES: biostudies-literature

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Comparative study of catalytic activities among transition metal-doped IrO2 nanoparticles.

Lee Hangil H Kim Joo Yeon JY Lee Si Young SY Hong Jung A JA Kim Namdong N Baik Jaeyoon J Hwang Yun Jeong YJ

Scientific reports 20181113 1

Catalytic activities of transition metal-doped IrO2 nanoparticles (TM-IrO2 NPs; TM = Cr, Mn, Fe, Co, or Ni) are compared for various oxidation reactions such as electrochemical oxygen evolution reaction (OER), gas-phase photo-oxidation of thiol function group, and CO oxidative conversion. Here, we discovered a series of TM-IrO2 catalysts have a common activity trend for these oxidation reactions, and their activities are closely related with modified electronic s ...[more]

PMID: 30425306

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Project description:Herein, we report on developing a facile synthetic route for reusable nanocatalysts based on a combination of the supermagnetic properties of magnetite with the unique optical and catalytic properties of noble metal hybrid nanomaterials. We compare two different synthetic methods, to find out which is best from synthetic and application points of view, for the synthesis of Fe3O4 and Fe3O4@M (M = Ag or Au) core-shell hybrid nanostructures. The two different single-step synthetic methods are: thermal decomposition and hydrothermal. The structural, morphological and magnetic properties of the obtained Fe3O4 and Fe3O4@M nanoparticles were characterized by various techniques. XRD of the Fe3O4 nanoparticles exhibited sharp and strong diffraction peaks, confirming the highly crystalline structure of the Fe3O4 particles synthesized by the hydrothermal method, while broad and weak peaks were observed on using the thermal decomposition method. Both Fe3O4@Ag and Fe3O4@Au core-shells obtained by the hydrothermal method showed the reflection planes of Fe3O4 and additional planes of Ag or Au. But on the formation of Fe3O4@Ag/Au by the thermal decomposition method the peak for Fe3O4 disappeared and only the diffraction peaks of Ag or Au appeared. According to TEM analysis there was a broad particle-size distribution, random near-spherical shapes and slight particle agglomeration for Fe3O4 synthesized by the thermal decomposition method. However, there was a moderate size distribution, spherical shapes and well-dispersed particles without large aggregations for the hydrothermal method. TEM images of the synthesized nanoparticles by the two methods used showed a pronounced difference in both size and morphological shape. The catalytic performance of the synthesized nanoparticles was examined for the reduction of Congo red dye in the presence of NaBH4. The Fe3O4 nanocatalyst maintained its catalytic activity for only one cycle. In the cases of Fe3O4@Au and Fe3O4@Ag, the catalytic activity was conserved for four and ten successive cycles, respectively. Based on the obtained results, it was concluded that the hydrothermal synthesis of Fe3O4, Fe3O4@Ag and Fe3O4@Au nanostructures is highly recommended due to their selectivity and merits.

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Comparative study of catalytic activities among transition metal-doped IrO₂ nanoparticles.

Publications

Comparative study of catalytic activities among transition metal-doped IrO<sub>2</sub> nanoparticles.

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