Browsing by Author "Cheng, Yuan-Chung"

Now showing 1 - 2 of 2

Perfluoro-Functionalized Conducting Polymers Enhance Electrocatalytic Oxygen Reduction
(2020-01-01)
Mansoure, Tharwat Hassan
;
Ayalew, Hailemichael
;
Kao, Wei-Lun
;
Shyue, Jing-Jong
;
Luo, Shyh-Chyang
In this study, films of perfluoro-functionalized poly(3,4-ethylenedioxythiophene) [poly(EDOT-F)] were prepared directly through electropolymerization for use as catalysts for the oxygen reduction reaction (ORR), applying the rotating ring disk electrode technique. Poly(EDOT-F) operated catalytically through a two-electron and/or mixed pathway. Spinel Co3O4 nanospheres were introduced into poly(EDOT-F) to enhance its ORR performance and electron transfer number (n). Benefiting from its unique interconnected pore structure and its resemblance to the binder Nafion, poly(EDOT-F) could be used as a single replacement for both the binder and the carbon support required for the spinel Co3O4 nanospheres. The Co3O4/poly(EDOT-F) composite, when used as an electrode, exhibited a limiting current density of -4.761 mA cm(-2) at 0.18 V (vs RHE) (cf. 20% Pt/C: -3.615 mA cm(-2)), an onset potential of 0.99 V (cf. 20% Pt/C: 0.938 V), and a half-wave potential of 0.628 V (cf. 20% Pt/C: 0.727 V) in 0.1 M aqueous KOH. The electron transfer number of the Co3O4/poly(EDOT-F) nanocomposite in the ORR was 3.84, suggesting a desirable four-electron pathway. This high electrocatalytic activity presumably resulted from the synergistic effect of the Co3O4 nanospheres and the poly(EDOT-F) polymer, which created many more active sites, enhanced the electron transfer kinetics, and eventually improved the ORR performance.
Reversible adapting layer produces robust single-crystal electrocatalyst for oxygen evolution
(2015-08-01)
Tung, Ching-Wei
;
Hsu, Ying-Ya
;
Shen, Yen-Ping
;
Zheng, Yixin
;
Chan, Ting-Shan
Electrochemically converting water into oxygen/hydrogen gas is ideal for high-density renewable energy storage in which robust electrocatalysts for efficient oxygen evolution play crucial roles. To date, however, electrocatalysts with long-term stability have remained elusive. Here we report that single-crystal Co3O4 nanocube underlay with a thin CoO layer results in a high-performance and high-stability electrocatalyst in oxygen evolution reaction. An in situ X-ray diffraction method is developed to observe a strong correlation between the initialization of the oxygen evolution and the formation of active metal oxyhydroxide phase. The lattice of skin layer adapts to the structure of the active phase, which enables a reversible facile structural change that facilitates the chemical reactions without breaking the scaffold of the electrocatalysts. The single-crystal nanocube electrode exhibits stable, continuous oxygen evolution for 41,000 h. This robust stability is attributed to the complementary nature of defect-free single-crystal electrocatalyst and the reversible adapting layer.