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Fahimi, Z, Moradlou O, Sabbah A, Chen K-H, Chen L-C, Qorbani M.  2022.  Co3V2O8 hollow spheres with mesoporous walls as high-capacitance electrode for hybrid supercapacitor device, 2022. 436:135225. AbstractWebsite

Bimetal oxides are promising materials in the field of energy storage due to their various oxidation states, synergistic interactions among multiple metal species, and stability. In this work, Co3V2O8 hollow spheres are synthesized by a two-step hydrothermal method: (i) synthesis of V2O5 spheres and (ii) partial replacement of V by Co through the Kirkendall effect. As an electrode, it shows an extrinsic pseudocapacitive charge-storage mechanism due to different oxidation states of V and Co ions. Because of the low crystallinity degree of the mesoporous wall and high accessible surface area of hollow spheres, the optimum Co3V2O8 electrode reaches a high specific capacitance of 2376F g−1 at a current density of 2 A g−1, which is more than two times higher than the top reported values, and a rate capability retention of ∼80% at 20 A g−1. Using Co3V2O8, activated carbon, and KOH as positive, negative electrodes, and electrolyte, respectively, a hybrid supercapacitor device presents maximum energy and power densities of 59.2 Wh kg−1 and 36.6 kW kg−1, respectively. Further, the aqueous supercapacitor device shows superior structural and electrochemical stabilities after 10,000 galvanostatic charge–discharge cycles because of the arrays of voids in the orthorhombic crystal structure of Co3V2O8 that can decrease the volume expansion/shrinkage during the intercalation/deintercalation processes. Our results provide a platform for exploring bimetallic Co and V-based oxides, hydroxides, and sulfides nanostructures as promising energy storage materials in the future.

Fang, WC, Huang JH, Sun CL, Chen* LC, Papakonstantinou P, Chyan OM, Chen KH.  2006.  Superior electrochemical performance of CNxNTs using TiSi2buffer layer on Si substrates. J. Vac. Sci. Tech.. B24:87-90.
Fang, S-L, Chou T-chin, Samireddi S, Chen K-H, Chen L-C, Chen W-F.  2017.  Enhanced hydrogen evolution reaction on hybrids of cobalt phosphide and molybdenum phosphide, 2017/03/01. Royal Society open science. 4(3):161016161016-161016.: The Royal Society Publishing AbstractWebsite

Production of hydrogen from water electrolysis has stimulated the search of sustainable electrocatalysts as possible alternatives. Recently, cobalt phosphide (CoP) and molybdenum phosphide (MoP) received great attention owing to their superior catalytic activity and stability towards the hydrogen evolution reaction (HER) which rivals platinum catalysts. In this study, we synthesize and study a series of catalysts based on hybrids of CoP and MoP with different Co/Mo ratio. The HER activity shows a volcano shape and reaches a maximum for Co/Mo = 1. Tafel analysis indicates a change in the dominating step of Volmer-Hyrovský mechanism. Interestingly, X-ray diffraction patterns confirmed a major ternary interstitial hexagonal CoMoP(2) crystal phase is formed which enhances the electrochemical activity.

Fang, WC, Huang* JH, Chen LC, Chen KH, Su OYH.  2007.  Influence of catalyst oxidation on the growth of nitrogen-containing carbonnanotubes for energy generation and storage applications. Diamond Relat. Mater.. 16:1140-1143.
Fang, WC, Huang* JH, Chen LC, Su OYL, Chen KH.  2006.  Effect of temperature annealing on capacitive and structural properties of hydrous ruthenium oxides. J. Power Sources . 160:1506-1510.
Fang, WC, Huang* JH, Chen LC, Su YO, H.Chen K, Sun CL.  2006.  Carbon nanotubes directly grown on Ti electrodes and enhancement in their electrochemical properties by nitric acid treatment. Electrochemical and Solid-State Lett.. 9:A5.
Fang, WC, Huang JH, Sun CL, Chen* KH, Chyan OM, Wu CT, Chen CP, Chen LC.  2007.  Arrayed nanocomposites directly grown on Ti-buffered silicon substrate for miniaturized supercapacitor applications. Electrochem. Comm.. 9:239-244.
Fang, WC, Huang JH, Sun CL, Chen* LC, Papakonstantinou P, Chyan OM, Chen KH.  2006.  Enhanced electrochemical properties of arrayed CNxnanotubes directly grown on Ti-buffered silicon substrates. Electrochemical and Solid State Lett.. 9:A175-A178.
Fang*, WC, Leu MS, Chen KH, Chen LC.  2008.  Ultrafast charging-discharging capacitive property of RuO2nanoparticles on carbon nanotubes using nitrogen incorporation. J. Electrochem. Soc.. 155:K15-K18.
Fang*, WC, Leu MS, Chen KH, Chen LC, Huang JH.  2007.  Effect of structural morphology on electrochemical properties of carbon nanotubes directly grown on Ti foil. Electrochemical and Solid-State Lett.. 10:K60-K62.
Fathabadi, M, Qorbani M, Sabbah A, Quadir S, Huang C-Y, Chen KH, Chen L-C, Naseri N.  2022.  Ultrathin amorphous defective co-doped hematite passivation layer derived via in-situ electrochemical method for durable photoelectrochemical water oxidation, 2022. Journal of Materials Chemistry A. :-.: The Royal Society of Chemistry AbstractWebsite

Although hematite (i.e., α-Fe2O3) has been widely investigated in photoelectrochemical water oxidation studies due to its high theoretical photocurrent density, it still suffers from serious surface charge recombination and low photoelectrochemical stability. Here we report an in-situ electrochemical method to form a uniform and ultrathin (i.e., 3–5 nm) passivation layer all over the porosities of the optimized ~3.2% Ti-doped α-Fe2O3 photoanode. We unveil the amorphous and defective nature of the in-situ derived layer assigning to a high concentration of oxygen vacancy and intercalated potassium atoms there, i.e., the formation of Ti/K co-doped defective α-Fe2O3-x. Owing to the efficient passivation of surface states, alleviated surface-potential fluctuations, and low charge-transfer resistance at the interface, photoanodes show an average of ~60% enhancement in the photoelectrochemical performance, applied bias absorbed photon-to-current efficiency of 0.43%, and Faradaic efficiency of ~88%. Moreover, the passivation layer prevents direct contact between the electrode material and electrolyte, resulting in less degradation and outstanding photoelectrochemical stability with photocurrent retention of ~95% after ~100 hours, albeit by performing several successive in-situ electrochemical passivation processes. This work presents an industrially scalable method to controllably engineer the interfaces of semiconductors–electrolytes with precious metal-free defective hematite-based co-catalysts for sustainable photoelectrochemical solar-to-fuel conversion applications.

Fu, F-Y, Fan C-C, Qorbani M, Huang C-Y, Kuo P-C, Hwang J-S, Shu G-J, Chang S-M, Wu H-L, Wu C-I, Chen K-H, Chen L-C.  2022.  Selective CO2-to-CO photoreduction over an orthophosphate semiconductor via the direct Z-scheme heterojunction of Ag3PO4 quantum dots decorated on SnS2 nanosheets, 2022. Sustainable Energy & Fuels. 6(19):4418-4428.: The Royal Society of Chemistry AbstractWebsite

Direct Z-scheme heterojunctions are widely used for photocatalytic water splitting and CO2 reduction due to facilitating well-separated photogenerated charge carriers and spatial isolation of redox reactions. Here, using a facile two-step hydrothermal and ion-exchange method, we uniformly decorate silver orthophosphate (i.e., Ag3PO4) quantum dots with an average characteristic size of ∼10 nm over tin(iv) sulphide (i.e., SnS2) nanosheets to form a 0D/2D heterojunction. The direct Z-scheme mechanism, i.e. charge transport for efficient electron (from SnS2) and hole (from Ag3PO4) recombination, is confirmed by the following experiments: (i) ultraviolet and X-ray photoelectron spectroscopies; (ii) photodeposition of Pt and PbO2 nanoparticles on reduction and oxidation sites, respectively; (iii) in situ X-ray photoelectron spectroscopy; and (iv) electron paramagnetic resonance spectroscopy. Owing to the photoreduction properties of Ag3PO4 with orthophosphate vacancies, Z-scheme charge carrier transfer, and efficient exciton dissociation, an optimized heterojunction shows a high CO2-to-CO reduction yield of 18.3 μmol g−1 h−1 with an illustrious selectivity of ∼95% under light illumination, which is about 3.0 and 47.8 times larger than that of Ag3PO4 and SnS2, respectively. The carbon source for the CO product is verified using a 13CO2 isotopic experiment. Moreover, by tracing the peak at ∼1190 cm−1 in the dark and under light irradiation, in situ diffuse reflectance infrared Fourier transform spectroscopy demonstrates that the CO2 reduction pathway goes through the COOH* intermediate.

Fu, F-Y, Shown I, Li C-S, Raghunath P, Lin T-Y, Billo T, Wu H-L, Wu C-I, Chung P-W, Lin M-C, Chen L-C, Chen K-H.  2019.  KSCN-induced Interfacial Dipole in Black TiO2 for Enhanced Photocatalytic CO2 Reduction, 2019. ACS Applied Materials & InterfacesACS Applied Materials & Interfaces. 11(28):25186-25194.: American Chemical Society AbstractWebsite
Fu, SP, Yu CJ, Chen TT, Hsu GM, Chen MJ, Chen* LC, Chen KH, Chen YF.  2007.  Anomalous optical properties of InN nanobelts: evidence of surface band bending and photoelastic effect. Adv. Mater.. 19:4524-4529.