Showing papers by "Kuei-Hsien Chen published in 2017"
TL;DR: In this article, an electrochemical technique as a cost-effective and one-step approach was utilized to fabricate graphene quantum dots (GQDs) Different amounts of GQDs (0, 02, 04, 08, and 12 wt %) were decorated uniformly on the surface of anodized ZnO nanowires (NWs) forming GQD/ZnO NWs.
Abstract: Herein, an electrochemical technique as a cost-effective and one-step approach was utilized to fabricate graphene quantum dots (GQDs) Different amounts of GQDs (0, 02, 04, 08, and 12 wt %) were decorated uniformly on the surface of anodized ZnO nanowires (NWs) forming GQD/ZnO NWs Transmission electron microscopy and atomic force microscopy confirmed formation of GQDs on the ZnO NWs, 12–22 nm in width and 1–3 graphene layers thick X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy were employed to verify the functional groups on the surface of GQDs, and the results indicated that GQDs readily anchored on the surface of ZnO NWs The GQD/ZnO NWs exhibited a considerable improvement on the photocatalytic degradation of methylene blue under solar irradiation, due to efficient light absorption In addition, the results indicated that the optimized GQD (04 wt %)/ZnO NWs showed the highest photoactivity with about 3-fold enhancement as compared to pure ZnO NWs Finally, a mechani
100 citations
TL;DR: In this paper, a template-directed ordered assembly was used to grow cobalt oxide (Co3O4) nanoflakes, using a sequential-electrodeposition process, into spherically porous sponge-like few-layer partially reduced graphene oxide (SrGO) synthesized by template-directed ordered assembly.
Abstract: The controlled growth of metal oxide nanostructures within hierarchically porous conductive carbon-based frameworks is critically important to achieving high volumetric performance and appropriate channel size for energy storage applications. Herein, we grow cobalt oxide (Co3O4) nanoflakes, using a sequential-electrodeposition process, into spherically porous sponge-like few-layer partially reduced graphene oxide (SrGO) synthesized by template-directed ordered assembly. Maximum specific/volumetric capacitances of 1112 F gCo3O4−1 (at 3.3 A gCo3O4−1), 178 F cm−3 (at 2.6 A cm−2), and 406 F gtotal−1 (at 1 A gtotal−1) and sensible rate capability (80% retention by increasing the charge/discharge current from 1 A g−1 to 16 A g−1) are obtained for the Co3O4 nanoflakes@SrGO hybrid electrodes. Besides, an asymmetric supercapacitor is made with the Co3O4[63%]@SrGO[37%] hybrid and activated carbon as a positive and a negative electrode, respectively. Electrochemical results indicate an energy density of 23.3 W h kg−1 at a high power density of 2300 W kg−1 (discharge time of about 42 s) and 62% retention even at a remarkable power density of 36 600 W kg−1 (discharge time of 1.6 s). Moreover, it shows excellent cycling stability with no decay after 20 000 charge/discharge cycles. This performance is attributed to the unique pore-sizes for an ion to channel into the porous structures, conductivity, and mechanical stability of the SrGO framework, which makes it promising for next-generation supercapacitors.
91 citations
TL;DR: In this article, SBA-15 nanoparticles containing P123 surfactant were used as fillers to see the effect of pore-directing agent on the performance of resultant composite membranes.
29 citations
TL;DR: The surface morphology of S4PH-x-PSs and Nafion 212 was investigated by atomic force microscopy and related to the percolation limit and proton conductivity, and it was confirmed from polarization curves that the fuel cell performance was not as high as that of Nafions under fully hydrated state due to higher interfacial resistance between S4 PH-35-PS and electrodes.
Abstract: Novel sulfonated poly(ether sulfone) copolymers (S4PH-x-PSs) based on a new aromatic diol containing four phenyl substituents at the 2, 2′, 6, and 6′ positions of 4,4′-diphenyl ether were synthesized. Sulfonation was found to occur exclusively on the 4 position of phenyl substituents by NMR spectroscopy. The ion exchange capacity (IEC) values can be controlled by adjusting the mole percent (x in S4PH-x-PS) of the new diol. The fully hydrated sulfonated poly(ether sulfone) copolymers had good proton conductivity in the range 0.004–0.110 S/cm at room temperature. The surface morphology of S4PH-x-PSs and Nafion 212 was investigated by atomic force microscopy (tapping-mode) and related to the percolation limit and proton conductivity. Single H2/O2 fuel cell based on S4PH-40-PS loaded with 0.25 mg/cm2 catalyst (Pt/C) exhibited a peak power density of 462.6 mW/cm2, which was close to that of Nafion 212 (533.5 mW/cm2) at 80 °C with 80% RH. Furthermore, fuel cell performance of S4PH-35-PS with various relative hu...
23 citations
TL;DR: In this article, a bimetallic macrocyclic-N4 complex, FCC, consisting of a Co-corrole core equipped with a peripheral ferrocene has been synthesized.
Abstract: A bimetallic macrocyclic-N4 complex, FCC, consisting of a Co-corrole core equipped with a peripheral ferrocene has been synthesized. The complex structure was thoroughly characterized using single crystal X-ray diffraction. The Co-corrole, mono-substituted with a peripheral Fe-complex, exhibited unique characteristics after its pyrolysis for oxygen reduction reaction (ORR) activity. Carbon black supported FCC, pyrolyzed at 500 °C, gives an electrocatalyst with a bimetallic (Co and Fe) active center, which facilitates ORR via a 4-electron pathway. The new non-precious bimetallic electrocatalyst exhibits a high electron transfer number of more than 3.95, with a H2O2 yield of below 2.3%, over the potential range of 0.2–0.8 V for ORR in acidic medium, which is superior to pyrolyzed Co-corroles. The enhanced ORR activity for the catalyst derived from this technique provides a new prospect for next-generation non-precious N4 electrocatalysts for fuel cell applications.
21 citations
TL;DR: Dielectric investigations of the Sm-based MOF provide an effective path for the development of high dielectric materials in the future.
Abstract: The self-assembly of a samarium-based metal–organic framework [Sm2(bhc)(H2O)6]n (1) in good yield was achieved by reacting Sm(NO3)3·6H2O with benzenehexacarboxylic acid (bhc) in a mixture of H2O–EtOH under hydrothermal conditions. A structural analysis showed that compound 1 crystallized in a space group of Pnmn and adopted a 3D structure with (4,8) connected nets. Temperature dependent dielectric measurements showed that compound 1 behaves as a high dielectric material with a high dielectric constant (κ = 45.1) at 5 kHz and 310 K, which is comparable to the values for some of the most commonly available dielectric inorganic metal oxides such as Sm2O3, Ta2O5, HfO2, and ZrO2. In addition, electrical measurements of 1 revealed an electrical conductivity of about 2.15 × 10–7 S/cm at a frequency of 5 kHz with a low leakage current (Ileakage = 8.13 × 10–12 Amm–2). Dielectric investigations of the Sm-based MOF provide an effective path for the development of high dielectric materials in the future.
17 citations
TL;DR: In this article, the pseudorapidity separation (Delta eta) of the particle pair at small relative azimuthal angle (abs(Delta phi) < pi/3) is decomposed into a jet component that dominates the short-range correlations and a component that persists at large Delta eta and may originate from collective behavior of the produced system.
Abstract: Two-particle correlations in pPb collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV are studied as a function of the pseudorapidity separation (Delta eta) of the particle pair at small relative azimuthal angle (abs(Delta phi)< pi/3). The correlations are decomposed into a jet component that dominates the short-range correlations (abs(Delta eta) < 1), and a component that persists at large Delta eta and may originate from collective behavior of the produced system. The events are classified in terms of the multiplicity of the produced particles. Finite azimuthal anisotropies are observed in high-multiplicity events. The second and third Fourier components of the particle-pair azimuthal correlations, V[2] and V[3], are extracted after subtraction of the jet component. The single-particle anisotropy parameters v[2] and v[3] are normalized by their lab frame mid-rapidity value and are studied as a function of eta[cm]. The normalized v[2] distribution is found to be asymmetric about eta[cm] = 0, with smaller values observed at forward pseudorapidity, corresponding to the direction of the proton beam, while no significant pseudorapidity dependence is observed for the normalized v[3] distribution within the statistical uncertainties.
17 citations
TL;DR: X-ray diffraction patterns confirmed a major ternary interstitial hexagonal CoMoP2 crystal phase is formed which enhances the electrochemical activity and indicates a change in the dominating step of Volmer–Hyrovský mechanism.
Abstract: Production of hydrogen from water electrolysis has stimulated the search of sustainable electrocatalysts as possible alternatives. Recently, cobalt phosphide (CoP) and molybdenum phosphide (MoP) re...
16 citations
TL;DR: Inspired by geogrids commonly applied in construction engineering to reinforce side slopes and retaining walls, the use of a "nano-geogrid" to reinforce a CuxZnySnzS (CZTS) electrode for application in electrochemical reactions is demonstrated in this paper.
Abstract: Inspired by geogrids commonly applied in construction engineering to reinforce side slopes and retaining walls, the use of a “nano-geogrid” to reinforce a CuxZnySnzS (CZTS) nanowall electrode for application in electrochemical reactions is demonstrated. The CZTS nanowall electrode reinforced by the nano-geogrid (denoted as NWD) shows not only remarkable mechanical and electrochemical stability but also considerable electrochemical performances. The NWD demonstrated as a counter electrode in a dye-sensitized solar cell shows a power conversion efficiency of 7.44 ± 0.04%, comparable with the device using Pt as electrode, and also significantly improves device stability as compared with that afforded by an electrode comprising a CZTS nanowall without the nano-geogrid (denoted as NOD). In addition, applying the NWD electrode as a cathode in photo-electrochemical hydrogen evolution reactions (HERs) yields a photocurrent density of −10 mA cm−2 at −0.162 V (vs RHE) under AM 1.5 illumination. Moreover, when HERs are conducted under extreme conditions, the NWD electrode remains intact, whereas the NOD electrode is completely peeled off after 10 min of reaction. Therefore, the concept of using a mimetic rational nanostructure could pave the way for the possibility of improving the performance and stability of various devices.
14 citations
TL;DR: In this paper, the performance of a carbon-black-supported pyrolyzed vitamin B9 (folic acid)-treated cathode catalyst (py-Fe-FA/C) in the oxygen reduction reaction (ORR) and proton exchange membrane fuel cell (PEMFC) was investigated.
Abstract: This study presents the performance of a carbon-black-supported pyrolyzed vitamin B9 (folic acid)-treated cathode catalyst (py-Fe-FA/C) in the oxygen reduction reaction (ORR) and proton exchange membrane fuel cell (PEMFC). Electrochemical ORR measurements revealed that using py-Fe-FA/C resulted in excellent ORR activity through the direct four-electron reduction pathway. The H2–O2 PEMFC with py-Fe-FA/C in the cathodic side produces a maximum power density of 330 mW cm–2 with the 80 °C operation temperature and the 1 atm back pressure. X-ray photoelectron spectroscopy and in situ X-ray adsorption spectroscopy proved that the enhanced ORR activity was caused by the network structure of polyaromatic hydrocarbons, quaternary-type (graphitic) nitrogen, and the coordination structure of the py-Fe-FA/C, as confirmed by the ORR mechanism study using detailed XPS and in situ X-ray adsorption spectroscopy. Particularly, in situ X-ray adsorption spectroscopy elucidated the ORR mechanism of the py-Fe-FA/C.
13 citations
TL;DR: In this paper, a mixture of trioctylphosphine oxide (TOPO) and oleylamine (OLA) was used as a solvent to control the formation of CZTS NPs.
TL;DR: In this article, the structural and optical properties of the epitaxial ZnO films have been characterized using theta-two theta and phi scans, X-ray diffraction, rocking curve, and photoluminescence measurements.
Abstract: Photoconduction (PC) properties in the ZnO films with the (110) nonpolar surface (a-plane) epitaxially grown by chemical vapor deposition on the LiGaO2 (010) substrates with low lattice mismatches (4.0% along the c-axis and 3.8% along the m-axis) have been studied. The structural and optical qualities of the epitaxial films have been characterized using theta-two theta and phi scans, X-ray diffraction, rocking curve, and photoluminescence measurements. The nonpolar ZnO film exhibits a near visible-blind ultraviolet photoresponse. The optimal photocurrent to dark current ratio (i.e., sensitivity) can reach 13360%. The responsivity of the a-plane ZnO photoconductor-type detector can also reach 17 AW−1, which is two to four orders of magnitude higher than those of the m-plane, a-plane, and r-plane photodiodes based on ZnO/ZnMgO quantum wells. The normalized gain at 2.9 cm2V−1 of the nonpolar film is also comparable with the optimal recorded value of the ZnO nanowires. In addition, the PC mechanism has also b...
Patent•
19 Jan 2017TL;DR: In this paper, an electrode structure consisting of a substrate, a buffer layer, and a nano-material layer is provided, where the structure of the nano material layer is nanowall.
Abstract: An electrode structure is provided. The electrode structure includes a substrate, a buffer layer, and a nano-material layer. The buffer layer is disposed on the substrate. The nano-material layer is disposed on the buffer layer, wherein the structure of the nano-material layer is nanowall.
Patent•
16 Jan 2017
TL;DR: In this article, an electrode structure including a substrate, a buffer layer and a nano-material layer is provided, and the buffer layer is disposed on the substrate and the nano material layer is placed on the buffer.
Abstract: An electrode structure is provided The electrode structure includes a substrate, a buffer layer and a nano-material layer The buffer layer is disposed on the substrate The nano-material layer is disposed on the buffer layer, wherein the morphology of the nano-material layer is nanowall