Browsing by Author "Sun, Yu"

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Chemical bath deposition of IrO2 films on ITO substrate
(2014-11-01)
Chen, Jing-Yu
;
Chen, Yong-Min
;
Sun, Yu
;
Lee, Jyh-Fu
;
Chen, San-Yuan
A chemical bath is shown to deposit an IrO2 film on an ITO substrate. The chemical bath is prepared by mixing an Ir precursor (Na3IrCl6 center dot xH(2)O), an oxidizer (NaClO), a complexing agent (NaNO2), and a complex agent/stabilizer (NaOH) in an aqueous solution at a molar ratio of 1:1.5:10:30. From the UV-vis absorption spectra, complexes such as [Ir(OH)(6)]m(3-), [Ir(NO2)(4)Cl-2](3-), and [Ir(NO2)(3)Cl-3](3-) are identified. These complexes are relatively stable, minimizing the undesirable homogeneous precipitation of IrO2 nanoparticles in favor of the heterogeneous growth of the IrO2 film on the ITO substrate. Diffraction patterns from the as-deposited IrO2 film reveal an amorphous structure. In addition, profiles from X-ray absorption spectroscopy and X-ray photoelectron spectroscopy indicate that the oxidation state of the Ir in the as-deposited IrO2 film is +4. Thermogravimetric analysis confirms the inclusion of 10 wt% hydrated water in the as-deposited IrO2 film. Scanning electron microscope images reveal a continuous solid film with a smooth surface. The amorphous IrO2 film becomes rutile IrO2 phase after a mild heat treatment in air. (c) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Synthesis of Pd9Ru@Pt nanoparticles for oxygen reduction reaction in acidic electrolytes
(2015-03-01)
Sun, Yu
;
Hsieh, Yu-Chi
;
Chang, Li-Chung
;
Wu, Pu-Wei
;
Lee, Jyh-Fu
Nanoparticles of PdRu, Pd3Ru, and Pd9Ru are synthesized and impregnated on carbon black via a wet chemical reflux process. X-ray diffraction patterns of the as-synthesized samples, PdxRu/C (x = 1/3/9), suggest successful formation of alloy without presence of individual Pd and Ru nanoparticles. Images from transmission electron microscope confirm irregularly-shaped nanoparticles with average size below 3 nm. Analysis from extended X-ray absorption fine structure on both Pd and Ru K-edge absorption profiles indicate the Ru atoms are enriched on the surface of PdxRu/C. Among these samples, the Pd9Ru/C exhibits the strongest electrocatalytic activity for oxygen reduction reaction (ORR) in an oxygen-saturated 0.1 M aqueous HClO4 solution. Subsequently, the Pd9Ru/C undergoes Cu under potential deposition, followed by a galvanic displacement reaction to deposit a Pt monolayer on the Pd9Ru surface (Pd9Ru@Pt). The Pd9Ru@Pt reveals better ORR performance than that of Pt, reaching a mass activity of 0.38 mA mu g(pt)(-1), as compared to that of commercially available Pt nanopartides (0.107 mA mu g(pt)(-1)). The mechanisms responsible for the ORR enhancement are attributed to the combined effects of lattice strain and ligand interaction. In addition, this core-shell Pd9Ru@Pt electrocatalyst represents a substantial reduction in the amount of Pt consumption and raw material cost. (C) 2014 Elsevier B.V. All rights reserved.