Polymer Precursors Effect in the Macromolecular Metal-Polymer on the Rh/RhO 2 /Rh 2 O 3 Phase Using Solvent-Less Synthes
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Polymer Precursors Effect in the Macromolecular Metal‑Polymer on the Rh/RhO2/Rh2O3 Phase Using Solvent‑Less Synthesis and Its Photocatalytic Activity C. Diaz1 · M. L. Valenzuela2 · O. Cifuentes‑Vaca3 · M. Segovia1 Received: 1 April 2020 / Accepted: 18 June 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract A mixture of a nanostructured Rh/RhO2 phase was easily obtained by thermally treating the macromolecular Chitosan·(RhCl3)x precursor, while the Rh/Rh2O3 phase was obtained by pyrolyzing PSP-4-PVP·(RhCl3)x, precursors. The nature of the polymeric precursor acting as a solid-state template does not significantly influence the “foam-like” morphology of the Rh/ RhO2 and Rh/Rh2O3 nanoparticles. The size of the obtained products is within the range of 16 nm, as confirmed by HRTEM. A possible formation of the Rh/RhO2 and Rh/Rh2O3 nanoparticles is proposed. The bandgap values estimated from Tauc plots are 3.7 eV, and 3.0 eV for Rh/RhO2 and R h2O3, respectively. Their photocatalytic activity was measured, for the first time, using a methylene blue pollutant, achieving a photodegradation of 78% for Rh/RhO2 and 70% for Rh/Rh2O3 in 300 min.
1 Introduction From the precious metals of the periodic table, the Ir, Rh Pd, and Pt are the most catalytically active [1], and their activity is hugely enhanced at the nano-level [2, 3]. Among these, rhodium plays an essential role in several catalytic applications [4, 5]. However, the catalytic mechanism of rhodium materials is still elusive. Recent investigations suggest that the active centers could be in rhodium oxide rather than rhodium [5, 6], and the most common rhodium oxides are Rh2O3 and RhO2. Although they have a wide range of Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10904-020-01634-2) contains supplementary material, which is available to authorized users. * C. Diaz [email protected] * M. L. Valenzuela [email protected] 1
Departamento de Química, Facultad de Química, Universidad de Chile, La Palmeras 3425, Nuñoa, Casilla 653, Santiago de Chile, Chile
2
Instituto de Ciencias Químicas Aplicadas, Facultad de Ingeniería, Universidad Autónoma de Chile, Llano Subercaseaux 2801, San Miguel, Santiago de Chile, Chile
3
Facultad de Ciencias Exactas, Universidad Andrés Bello, Concepción, Autopista Concepción‑Talcahuano 7100, Talcahuano, Chile
applications in catalysis, scarce preparation methods of nanostructured Rh2O3 and RhO2 have been reported, and their morphological and size control remains poorly known [4, 5, 7–9]. All the described R h2O3 preparation methods are solution-based and solid-state methods that have not been reported yet. For instance, Rh(NO3)3 [7, 8], usually produces Rh oxides leading to R hO2 and R hO2 mixtures. Different mixtures can be obtained based on the thermal treatment temperature [8]. A mixture of α-and β-Rh2O3 can be obtained by heating to 797 °C, while a further increase up to 1000 °C is required to obtain pure β-Rh2O3 [8]. B
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