Browsing by Author "Wu, Pu-Wei"

Now showing 1 - 20 of 91

A combined electrochemical route to fabricate large-area and free-standing inverse opaline film
(2016-07)
Liao, Chen-Hong
;
Hung, Pei-Sung
;
Wu, Cheng-Yeou
;
Chen, Hsin-Yi
;
Wu, Pu-Wei
A combined electrochemical route involving electrophoresis and electrodeposition is developed to fabricate a large-area unsupported nickel inverse opaline film with thickness less than 10 pm. A vertical electrophoresis allows for the packing of 495 nm polystyrene microspheres on an ITO-coated glass to form a colloidal crystal with significantly reduced defects. Subsequently, a nickel electrodeposition is employed to fill the interstitial voids among the close-packed polystyrene microspheres, followed by the removal of the colloidal template in a two-stage process, leaving a robust nickel skeleton with hexagonally arranged pores and interconnected pore channels. This nickel skeleton is then detached from the ITO-coated glass via a liquid nitrogen treatment, rendering a free-standing nickel inverse opaline film in 2 x 2 cm(2). Porometer measurements indicate a narrow pore size distribution consistent with images from scanning electron microscope. We determine that the intensity ratio of (111)/(100) diffraction peak is an indicator for the strength of the Ni inverse opals, and thus affects its structural integrity upon detachment from the ITO-coated glass. (C) 2016 Elsevier B.V. All rights reserved.
A Combined Process of Liftoff and Printing for the Fabrication of Scalable Inkjet Printed Microstructures on a Flexible Substrate
(2015-04-01)
Fu, Yu-Min
;
Liang, Yen R.
;
Cheng, Yu-Ting
;
Wu, Pu-Wei
;
材料科學與工程學系
In this paper, a combined process of liftoff and printing (CPLoP) techniques is introduced to realize size-scalable printed silver microstructures with line widths ranging from 5 to 70 mu m and resistivities of similar to 9.8 mu Omega . cm on a flexible polyimide substrate via thermal sintering at 300 degrees C for 30 min. In addition, a printed interdigitated capacitor with an electrode line width and spacing of 10 mu m and a printed spiral square inductor with a 10-mu m line width and 5-mu m spacing in an area of 1 mm(2) have been successfully demonstrated with an area capacitance and inductance of 0.43 pF/mm(2) at 10 KHz and 1.054 mu H/mm(2) up to 100 KHz, respectively, which are the orders of magnitude performance improvement in comparison with the contemporary inkjet-printed capacitors and inductors. Owing to the significant reduction of energy demand in processing tools and waste generation in processing materials, the results have revealed that the CPLoP process can facilitate the advancement of printing manufacture technology for microelectronics applications.
A COMBINED PROCESS OF SILICON SHADOW MASKING AND INKJET PRINTING (SSMP) FOR MAKING GRAPHENE OXIDE AND REDUCED GRAPHENE OXIDE MICROSTRUCTURES FOR SELECTIVE CELL CULTURING APPLICATIONS
(2019-01-01)
Kang, Che-Hao
;
Fu, Yu-Min
;
Kao, Chin-Chuan
;
Yang, Jia-Wei
;
Tseng, Ming-Liang
This paper demonstrates a combined process of silicon shadow masking and inkjet printing (SSMP) to fabricate graphene oxide (GO) and reduced graphene oxide (rGO) line features with a width ranging from 20 to 70 mu m on varieties of substrates, such as PDMS, SiO2 , Kapton, etc. for selectively cell (RPE and PC-12 cells) culturing applications. The rGO with an electrical resistance of 33.48k Omega/ is characterized via a printed four point resistivity measurement structure. Owing to the characteristics of low chemical usage, low process temperature and complexity, and high fault tolerance of inkjet printers, the process technique has shown its potential for biomedical applications in terms of flexible cell culturing platform fabrication.
A cost-effective fabrication of iridium oxide films as biocompatible electrostimulation electrodes for neural interface applications
(2017-01-25)
Chen, Yong-Min
;
Chung, Tsai-Wei
;
Wu, Pu-Wei
;
Chen, Po-Chun
;
材料科學與工程學系
Electrostimulation medical devices for neural diseases require electroactive and biocompatible interface materials to transmit signals from electrodes to targeting tissues. Iridium oxide is an attractive ceramic material for neurostimulation electrodes due to its desirable stability and biocompatibility. In this study, we developed a cost effective and thickness controllable process to fabricate iridium oxide film by chemical bath deposition (CIROF). Surface morphology, crystallinity, roughness, hydrophilicity, and charge storage capacity as well as biocompatibility of the CIROFs with different thicknesses were analyzed. Accordingly, the CIROFs present rough and hydrophilic surfaces for cell attachment and good biocompatibility for cell viability. In addition, the charge storage capacity (CSC) of the as-deposited and the annealed CIROFs were 78.29 mC/cm(2) and 71.76 mC/cm(2), respectively. Consequently, these results show advantages that make the CIROF a promising neurostimulation electrode material for implantable medical devices in neural systems. (C) 2016 Elsevier B.V. All rights reserved.
A facile approach to fabricate Ni inverse opals at controlled thickness
(2009-11-15)
Huang, Yi-Jui
;
Lai, Chun-Han
;
Wu, Pu-Wei
;
Chen, Li-Yin
;
材料科學與工程學系
A vertical electrophoretic deposition method was employed to fabricate polystyrene (PS) colloidal crystals with negligible defects and considerable surface uniformity. Subsequently, the interstitial voids within the colloidal crystals were electroplated with Ni, followed by selective removal of the PS microspheres. With careful adjustment in the processing parameters. we were able to obtain Ni inverse opals at predetermined thickness in relatively short time. The inverse opals revealed superb structural stability and surface uniformity. Because the electrophoresis and electrodeposition were both carried out in a solution state, this fabrication scheme enables facile construction of inverse opals on conductive substrates over conventional approaches. (C) 2009 Elsevier B.V. All rights reserved.
A facile route to prepare PdPt alloys for ethanol electro-oxidation in alkaline electrolyte
(2011-01-31)
Lin, Sheng-Chieh
;
Chen, Jing-Yu
;
Hsieh, Yi-Fan
;
Wu, Pu-Wei
;
材料科學與工程學系
We adopted a displacement reaction in acidic solution that enabled the spontaneous reduction of Pd and Pt cations in conjunction with corrosive dissolution of Ni. The composition for the PdPt was adjusted by varying the concentration of Pd and Pt cations. From SEM images and XRD patterns, the PdPt formed an fcc alloy uniformly deposited on the Ni substrate. Electro-oxidation of ethanol was conducted in alkaline electrolyte for samples of Pd, Pt, and PdPt alloys. In cyclic voltammetric profiles, the Pd(77)Pt(23) revealed the highest electrocatalytic ability in both apparent current and mass activity, followed by Pd(87)Pt(13), Pd, and Pt. Similar behaviors were observed in life time measurements in which stable performances for ethanol electro-oxidation were obtained. (C) 2010 Elsevier B.V. All rights reserved.
A LOW TEMPERATURE INKJET PRINTING AND FILLING PROCESS FOR LOW RESISTIVE SILVER TSV FABRICATION IN A SU-8 SUBSTRATE
(2017-01-01)
Yang, Tsung-Han
;
Guo, Zi-Li
;
Fu, Yu-Min
;
Cheng, Yu-Ting
;
Song, Yen-Fang
The paper presents a low temperature (with 60 degrees C) inkjet printing and filling process to realize low resistive Ag TSV (Through Substrate Vias) with the aspect ratio of via depth vs. diameter from 2 to 5 in a SU-8 substrate potential for flexible microsystem packaging applications. Combining humidity control and layer-by-layer Ag mirror reaction, the proposed process technology can accomplish a fully filled TSV with the lowest electrical resistivity of similar to 450 mu Omega.cm in comparison with the prior printing and filling technologies.
A Strategy to Synthesize Ultrahigh-N-Doped Hierarchical Carbons via Induced beta-Sheet from Silk Fibroin by In Situ Electrogelation/Electropolymerization
(2020-04-27)
Liu, Ta-Chung
;
Li, Tsung-Yu
;
Hung, Pei-Sung
;
Liang, Chun-Wei
;
Wu, Szu-Chen
Silk fibroin (SF) is recognized for its rich nitrogen content and has been explored for its promising potential in energy storage because of its hexagonal pseudographitic structure from the direct transformation of the unique secondary protein beta-sheet peptides of carbonized SF. In this work, we proposed a novel strategy that combined with in situ electrophoresis and electrogelation of SF as well as the electropolymerization of 3,4-ethylenedioxythiophene (EDOT) for producing high-level nitrogen-doped (N-doped) carbons. A high beta-sheet content of SF can be synthesized in a three-dimensional (3D) inverse opaline skeleton via double-network microstructure (physical beta-sheet cross-linking and chemical PEDOT cross-linking) induced by the hydrophobic EDOTs. This synergistic effect regulating SF distribution and balancing the intra/intermoleeular hydrogen bonding among SF results in boosting beta-sheet contents. Herein, this 3D SF/PEDOT composite inverse opal (SPIO) exhibits a much ultrahigh-coneentrated beta-sheets (46.4%) compared to pure electrogelated SFIO with 16.4% of beta-sheets. After subsequent pyrolysis, a high-level (14.7%) N-doped pseudographitic carbon inverse opal is realized. For evaluation as a pseudocapacitor, this high-level N-doped pseudographitic carbon inverse opal shows a capacitance of 342 F g(-1) at 0.5 A g(-1) and a commendable energy density of 31.7 Wh kg(-1) at an ultrahigh power density of 25009 W kg(-1) (at 50 A g(-1)). After galvanostatic charging/discharging at 15 A g(-1) for 10000 cycles, the sample maintains an impressive capacitance retention of 89.8%.
An Inkjet Printing Technique for Scalable Microfabrication of Graphene-Based Sensor Components
(2020-01-01)
Fu, Yu-Min
;
Chou, Meng-Chuin
;
Kang, Che-Hao
;
Cheng, Yu-Ting
;
Wu, Pu-Wei
This paper presents a versatile and precise graphene patterning technique using the combined process of masking and inkjet printing. A graphene-based structure is fabricated by first defining the structural pattern and position using a masking mold, which can be either electroplated copper or deep reactive ion etching (DRIE) silicon shadow mask, followed by inkjet deposition of graphene ink and lift-off. The hybrid technique can realize high-fidelity, high-resolution graphene-based microstructures including free-standing and cantilever beams, four-point resistive measurement structures, and piezoresistive sensing elements with a minimum line width of similar to 20 mu m. Moreover, this method can facilitate the micropatterning of graphene oxide (GO) and reduced graphene oxide (rGO) on substrates such as polydimethylsiloxane (PDMS) and SiO2/Si for selective cell culturing applications. Owing to the characteristics of low chemical usage, low process temperature and complexity, and high fiexibility and fault tolerance of inkjet printing, this technique demonstrates compelling potential for a variety of biomedical applications.
Characteristic Improvement of Inkjet Printed Ag Interconnects Using Tape On-Off and Mirror-Reaction Processes
(2015)
Guo, Zi-Li
;
Fu, Yu-Min
;
Cheng, Yu-Ting
;
Shew, Bor-Yuan
;
Wu, Pu-Wei
In the paper, we develop and implement the processes of tape on-off and Ag mirror-reaction to the previously developed size scalable inkjet printing process technique, i.e. CPLoP (Combined Process of Lift-off and Printing) for continuing its future interconnect applications in flexible microelectronics. The newly developed processes not only reduce coffee ring effect but also improve better electrical conductivity of the printed Ag interconnects at low process temperature. A 10 mu m wide Ag interconnect with flat surface morphology and low electrical resistivity, i.e. 7.7 mu Omega center dot cm, has been realized.
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.
Chemical stability and electrical conductivity of BaCe0.4Zr0.4Gd0.1Dy0.1O3-delta perovskite
(2015-11-01)
Tsai, Yen-Chang
;
Chen, San-Yuan
;
Wang, Jeng-Han
;
Wu, Pu-Wei
;
Chen, Po-Chun
A proton-conducting BaCe0.4Zr0.4Gd0.1Dy0.1O3-delta (BCZGD) perovskite is fabricated via a wet chemical route using precursors including Ba(NO3)(2), Ce(NO3)(3)center dot 6H(2)O, ZrO(NO3)(4)center dot 6H(2)O, Gd(NO3)(3)center dot 6H(2)O, and Dy(NO3)(3)center dot 5H(2)O. The synthesis process involves the dissolution of relevant precursors and glycine in deionized water at proper molar ratios. Subsequently, the mixture undergoes a heat treatment at 1300 degrees C for 10 h in air to form the perovskite powders. The as-synthesized BCZGD powders are filtered and pressed at 440 MPa, following by a sintering at 1450 degrees C for 24 h in air to render a free-standing proton-conductive disk with a thickness of 850 mu m. Material characterization including scanning electron microscopy (SEM), X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), and electrical conductivity measurements are performed. The electrical conductivity of the BCZGD sample is recorded at 1.93 x 10(-3) S cm(-1) at 700 degrees C in a humid hydrogen atmosphere with an activation energy of 0.41 eV. TGA results confirm chemical stability of the BCZGD against carbon dioxide without any decomposition. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Combination of electrophoresis and electro-flocculation for the formation of adhering IrO2 pH sensing films
(2019-07-20)
Wang, Han-Yi
;
Hsieh, Yi-Chieh
;
Tso, Kuang-Chih
;
Chang, Chung-Kai
;
Cheng, Yu-Ting
We demonstrate a simple scheme to produce dense and adhering IrO2 thin films on ITO substrates via a bipolar pulsing process combining both electrophoresis and electro-flocculation. Our fabrication steps entail the synthesis of negatively-charged IrO2 nanoparticles in size of 3.5 nm using NaClO as an oxidizer in conjunction with Na3IrCl6, citric acid, and NaOH. Subsequently, multiple bipolar potentiostatic pulses are imposed in which alternating positive and negative potentials engender the electrophoresis of IrO2 nanoparticles, followed by their immediate coalescence facilitated by proton-catalyzed electro-floccu-lation. The resulting IrO2 thin films reveal impressive physical properties in surface uniformity, robust structural integrity, and strong adhesion to the substrate. The as-synthesized IrO2 thin film exhibits an amorphous nature with a pH sensing slope between -73.6 and -71.5 mV/pH, characteristic of super-Nernstian behavior. In contrast, the annealed IrO(2 )sample demonstrates a crystalline rutile phase with a pH sensing slope between -49.5 and -54.7 mV/pH, consistent with typical Nernstian response. Our approach provides a new route for the formation of strong and adhering oxide films from their colloidal constituents. (C) 2019 Elsevier Ltd. All rights reserved.
Combination of microspheres and sol-gel electrophoresis for the formation of large-area ordered macroporous SiO2
(2017-12-01)
Liao, Chen-Hong
;
Hung, Pei-Sung
;
Cheng, Yu
;
Wu, Pu-Wei
;
材料科學與工程學系
A simple and effective fabrication scheme involving sequential electrophoretic depositions of polystyrene (PS) microspheres (500 nm and 1 mu m in diameter) and SiO2 sols (similar to 5 nm in diameter) to produce large-area ordered macroporous SiO2 inverse opals (2 x 2 cm(2)) on ITO substrates is demonstrated. The zeta potentials for PS microsphere suspension and SiO2 sols are measured to determine an optimized processing window in which both samples carry negative surface charges and sol-gel transformation can be properly implemented. Our approach entails the electrophoresis of PS microspheres to render a colloidal crystal with negligible defects. Afterward, SiO2 sols are infiltrated to the interstitial voids among the closely-packed PS microspheres via another electrophoresis process, followed by an oxidation treatment to remove the PS colloidal template and complete the densification of SiO2 gels. The resulting SiO2 inverse opals reveal impressive surface uniformity and structural integrity. Fourier transform infrared spectroscopy confirms the complete removal of PS microspheres, leaving an intact SiO2 skeleton, whereas X-ray diffraction pattern indicates its amorphous nature.
Conformal deposition of Ni-P on anodic aluminum oxide template
(2008)
Lin, Sheng-Chieh
;
Lai, Chun-Han
;
Wu, Pu-Wei
;
材料科學與工程學系
;
Department of Materials Science and Engineering
A nanoporous semiconducting template was fabricated by conformal deposition of Ni-P over anodic aluminum oxide (AAO). Electroless plating was conducted in repeated steps of sensitization, activation, and deposition using NaH2PO2 as a reducing agent. Variables including pH, temperature, time, and additive were studied for conformal deposition within the pore channels without clogging the openings prematurely. We demonstrated concentric Ni-P tubes with an inner diameter of 84 nm at 10 mu m length. Resistivity of the AAO template was determined at 39.6 Omega cm for through-channel direction. Incorporation of the semiconducting AAO structure with established template synthesis technologies opens up the opportunity for numerous devices. (C) 2007 The Electrochemical Society.
Conformal deposition of Pt on titania nanotubes to produce a bio-electrode for neuro-stimulating applications
(2018-03-01)
Wu, Yi-Jia
;
Chung, Tsai-Wei
;
Huang, Jun-Qian
;
Wu, Pu-Wei
;
Chen, Po-Chun
We develop an alkaline electroless bath for deposition of a conformal Pt layer 40 nm thick on titania nanotubes 800 nm long. The charge storage capacity (CSC) and electrochemically active surface area (ECSA) of this Pt-coated titania nanotube array have been studied to evaluate its potential as a bio-electrode for implantable bioelectronic devices. Images from electron microscopes confirm the formation of a uniform Pt film on both the internal and external surfaces of the nanotubes. The X-ray diffraction pattern indicates a preferred (111) orientation. Analysis from X-ray absorption spectroscopy on the plating bath suggests a reduction sequence of Pt4+ -> Pt2+ -> Pt. The Pt-coated titania nanotube array has large CSC and ECSA values, attributed to the hollow tubular nanostructure with a conformal Pt coating.
Conformal Deposition of RuO2 on Cu via a Galvanic Cementation Reaction
(2019-06-28)
Lin, Chun
;
Chou, Shih-Cheng
;
Tso, Kuang-Chih
;
Hsieh, Yi-Chieh
;
Chan, Ting-Shan
We develop a seedless wet chemical process to deposit uniform RuO2 on a Cu substrate. Our approach entails the synthesis of volatile RuO4 colloids in a pH 9 aqueous solution from the oxidation of RuCl52- by ClO-, followed by a galvanic cementation reaction in which the Cu undergoes a mild oxidation in conjunction with the reduction of RuO4 to produce a dense and conformal RuO2 thin film on the Cu surface. The nature for the chemical reactions and constituents involved are investigated by UV-Vis, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy. Both as-deposited and annealed RuO2 films are characterized by scanning electron microscope and X-ray diffractometer. The as-deposited RuO2 film, with a thickness of 199 nm, reveals an amorphous structure and after an Ar annealing, becomes crystalline in rutile phase. In between the RuO2 and Cu, there are presence of CuO from the displacement cementation reaction, and Cu2O from the parasitic Cu corrosion as expected from the Pourbaix diagram. These Cu oxides, with a thickness of 330 nm, provide sufficient adhesive bonding between RuO2 and Cu. (c) The Author(s) 2019. Published by ECS.
Conformal Electrodeposition of Co-Ni to Improve the Mechanical Properties of Three-Dimensional Ordered Macroporous Ni Films
(2020-01-22)
Wang, Guang-Ren
;
Hung, Pei-Sung
;
Chang, Shou-Yi
;
Yang, Jenn-Ming
;
Tseng, Yuan-Chieh
Three-dimensional ordered macroporous Ni films, known as Ni inverse opals, are fabricated via a template approach in which polystyrene (PS) microspheres (820 nm in diameter) are assembled in closely-packed colloidal crystals via a vertical electrophoresis process, followed by electroplating of Ni into the interstitial voids within the colloidal crystals and the selective removal of PS microspheres. To improve its mechanical strength, a conformal Ni-Co layer (45 similar to 64 nm) is electrodeposited on the skeletons of the Ni inverse opals by cyclic voltammetry. After coating, from nano-indentation tests, the hardness and reduced elastic modulus are enhanced considerably (172 similar to 220% for hardness; 72 similar to 79% for reduced elastic modulus), as compared to those of pristine inverse opals. After an annealing treatment for the interdiffusion of Ni and Co, the sample reveals an even stronger hardness. X-ray diffraction patterns indicate that the finite thickness of the inverse opals skeletons induces preferential growth of the (111) plane. In short, a combined effect of solid solution alloying, thickening of inverse opals skeletons for greater load bearing, and a predominant (111) plane is responsible for the improved mechanical strength of the Ni inverse opals. (C) 2020 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited.
Core-Shell Pd9Ru@Pt on Functionalized Graphene for Methanol Electrooxidation
(2018-01-01)
Kuo, Chih-Chia
;
Chou, Shih-Cheng
;
Chang, Yu-Chen
;
Hsieh, Yi-Chieh
;
Wu, Pu-Wei
A simple but effective electrochemical route to functionalize graphene is demonstrated. Cyclic voltammetric sweeps (CV) are performed in a 0.5 M H2SO4 aqueous solution on electrodes consisting of carbon cloth, graphene, and Nafion ionomer. Upon exposure to ambient oxygen, the formation of hydroxyl radicals from the oxygen reduction reaction during the CV cycles initiates the decomposition of the Nafion ionomer, which produces oxygenated functional groups on the graphene surface. Using contact angle measurements and X-ray photoelectron spectroscopy, various amounts of Nafion ionomer are explored to determine the optimum conditions for graphene functionalization. Afterwards, Pd9Ru nanoparticles with an average size of 3-4 nm are synthesized and impregnated on functionalized graphene (FGN). To prepare core-shell electrocatalysts, Pd9Ru/FGN is subjected to Cu underpotential deposition followed by a galvanic displacement reaction to deposit a Pt monolayer on the Pd9Ru surface (Pd9Ru@Pt). The assynthesized sample (Pd9Ru@Pt/FGN) exhibits enhanced performance in methanol electrooxidation, which includes abetter activity and lower susceptibility to poisoning by intermediates. The electrochemically active surface area (ECSA) of Pd9Ru@Pt/FGN shows a value that is 1.5-fold larger than that of Pd9Ru@Pt on untreated graphene (Pd9Ru@Pt/GN). In the durability tests, Pd9Ru@Pt/FGN and Pd9Ru@Pt/GN demonstrate losses in the ECSA of 14.9% and 30.3%, respectively. (C) 2018 The Electrochemical Society.
Dealloyed Pt2Os nanoparticles for enhanced oxygen reduction reaction in acidic electrolytes
(2014-05-05)
Lee, Yi-Juei
;
Hsieh, Yu-Chi
;
Tsai, Ho-Cheng
;
Lu, I-Te
;
Wu, Yue-Han
Carbon-supported Pt2Os (Pt2Os/C) nanoparticles in 3.55 nm sizes are synthesized from a wet chemical reflux process. Subsequently, the Pt2Os/C undergoes a dealloying treatment in which multiple cyclic voltammetric scans are imposed to dissolve the Os atoms selectively from the surface of the Pt2Os nanoparticles. X-ray diffraction signals from the dealloyed sample (DA-Pt2Os/C) indicate a fcc phase and composition analysis suggests Pt4Os. Line scans from the scanning transmission electron microscope confirm that the surface of Pt4Os is depleted with the Os atoms. This agrees with our quantum mechanics (Density Funtional theory) calculations, which predict for the Pt3Os composition that the surface skin layer is pure Pt. The DA-Pt2Os/C shows impressive electrocatalytic behaviors (0.29 mA mu g(Pt)(-1) in mass activity and 1.03 mA cm(Pt)(-2) in specific activity) for the oxygen reduction reaction (ORR) in oxygen-saturated 0.1 M aqueous HClO4 solution, as compared to those of commercially available Pt/C and as-synthesized Pt2Os/C. In stability test, the DA-Pt2Os/C demonstrates a better retention of ORR activities and a smaller loss of electrochemical active surface area. We verify experimentally that a four-electron step is responsible for the ORR process occurring on the DA-Pt2Os/C. (C) 2014 Elsevier B.V. All rights reserved.