Showing papers by "Kuo-Chuan Ho published in 2019"

Designing a carbon nanotubes-interconnected ZIF-derived cobalt sulfide hybrid nanocage for supercapacitors

Abstract: Owing to their advantages of high power density and a short charging duration, electrochemical supercapacitors (SCs) have received much attention as alternative energy systems for applications in portable electronic devices. The design of an electrode material with high capacitance and promising cycling stability will be a key factor for promoting the development of SC-based electronic systems. In this study, a hybrid structure of a cobalt sulfide nanocage derived from a zeolitic imidazolate framework (ZIF) and interconnected by carbon nanotubes (CNT/CoS) was designed and synthesized as an electrode material for SCs. Carbon nanotubes/ZIF-67 (CNT/ZIF-67) nanocomposites with controlled ZIF-67 particle sizes were systematically studied by varying the mass ratio of CNTs to ZIF-67 during crystallization, followed by subsequent sulfurization with thioacetamide. Benefiting from the porous nanocage architecture and conductive CNTs, the optimized CNT/CoS nanocage exhibited excellent electrochemical performance with an outstanding specific capacitance (2173.1 F g−1 at 5 A g−1) and high rate capability (65% retention at 20 A g−1). More importantly, a symmetric supercapacitor gave an energy density of 23.3 W h kg−1 at a power density of 3382.2 W kg−1 and impressive long-term stability (96.6% retention after 5000 cycles). These results suggest that the CNT/CoS nanocage is a promising composite for high-performance supercapacitor applications.

Platinum nanoparticles decorated graphene nanoribbon with eco-friendly unzipping process for electrochemical sensors

Abstract: In this study, an innovative large-scale synthesis of graphene nanoribbons (GNRs) with the eco-friendly unzipping process (only 0.1 mL H2SO4 acid solution for 1.0 mg carbon nanotube) was proposed. Nearly 100% yields of carbon nanotube derived GNRs was achieved by the proposed procedure. Through the longitudinal unzipping method, abundant oxygen-based functional groups were formed at the edges of GNRs, thus offering tremendous advantages for material synthesis and design. Furthermore, the reduction of platinum precursor to form platinum nanoparticles (PtNPs) can be facilitated by the functional groups on GNR surface for specific sensing. In fact, PtNPs played a role in connecting nodes to synergize the synthesized composite. The composite of PtNPs/GNRs could be further utilized as non-enzymatic biosensing materials against either oxidative or reductive analyte. Two essential biomarkers, namely hydrogen peroxide (H2O2) and β-nicotinamide adenine dinucleotide (NADH), were chosen to prove the feasibility of the proposed biosensors. From the experimental results of the amperometric analysis, sensitivities of the modified PtNPs/GNRs electrode toward H2O2 (378.5 µA/mM/cm–2) and NADH (724.3 µA/mM/cm–2) were obtained. The composite of PtNPs/GNRs has been verified to be a potential material for electrochemical biosensing with attractive sensitivity, selectivity, and stability.

Phase‐Engineered Weyl Semi‐Metallic MoxW1‐xTe2 Nanosheets as a Highly Efficient Electrocatalyst for Dye‐Sensitized Solar Cells

Abstract: The emerging Weyl semi-metals with robust topological surface states are very promising candidates to rationally develop new-generation electrocatalysts for dye-sensitized solar cells (DSSCs). In this study, a chemical vapor deposition (CVD) method to synthesize highly crystalline Weyl semi-metallic MoxW1-xTe2 nanocrystals, which are applied for the counter electrode (CE) of DSSCs for the first time, are employed. By controlling the temperaturedependent phase-engineered synthesis, the nanocrystal grown at 760 C exhibits the mixed phases of semiconducting Td& 2H-Mo0.32W0.67Te2.01 with charge carrier density of (1.20 0.02) 10 cm ; whereas, the nanocrystal synthesized at 820 C shows a single phase of semi-metallic TdMo0.29W0.72Te1.99 with much higher carrier density of (1.59 0.04) 10 cm . In the cyclic voltammetry (CV) analysis over 200 cycles, the MoxW1xTe2-based electrodes show better stability in the I /I3 electrolyte than a Pt electrode. In DSSC tests, a Td-Mo0.29W0.72Te1.99-decorated CE achieves the efficiency (η) of 8.85%, better than those CEs fabricated with Td& 2HMo0.32W0.67Te2.01 (7.81%) and sputtered Pt (8.01%). The electrochemical impedance spectra reveal that the Td-Mo0.29W0.72Te1.99 electrode possesses low charge-transfer resistance in electrocatalytic reactions. These exceptional properties make Weyl semi-metallic Td-MoxW1-xTe2 a potential electrode material for a wide variety of electrocatalytic applications.

Hierarchical urchin-like CoSe2/CoSeO3 electro-catalysts for dye-sensitized solar cells: up to 19% PCE under dim light illumination

Abstract: A hierarchical urchin-like structure of CoSe2/CoSeO3 (denoted as CoSe2/CoSeO3-UL) is synthesized by a one-step hydrothermal method and investigated as the electro-catalyst for the counter electrode (CE) of dye-sensitized solar cells (DSSCs). The evolution of the CoSe2/CoSeO3 nanostructures as a function of the synthesis time has been identified by scanning electron microscopy. The growth mechanism is proposed and the desired CoSe2/CoSeO3 hierarchical UL structure is noticed at 4 h. CoSe2/CoSeO3-UL consists of nanoparticles and hexagonal prisms for providing a high surface area for catalytic reactions and a one dimensional charge transport route, respectively. The results show that DSSCs using the CoSe2/CoSeO3-UL CE exhibit a higher power conversion efficiency (η) of 9.29 ± 0.24% than that of the cell using a Pt CE (8.33 ± 0.07%). Under various dim light conditions (i.e., a T5 lamp), the DSSC with the CoSe2/CoSeO3-UL CE shows outstanding η's of 19.88 ± 0.10%, 18.24 ± 0.06%, and 16.00 ± 0.13% at 7000 lux (2.21 mW cm−2), 6000 lux (1.89 mW cm−2) and 4800 lux (1.55 mW cm−2), respectively. This study demonstrates that CoSe2/CoSeO3-UL has great potential to replace Pt in DSSCs, and the application of DSSCs can be extended from outdoor to indoor conditions.