• Title/Summary/Keyword: Chemical reduction

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Mechanism of the Electrode Reduction of Cupferron in Neutral and Alkaline Media (중성 및 알카리성수용액에서 Cupferron 의 전극환원메카니즘)

  • Hwang, Kum-Sho;Hwang, Jung-Ui
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.11 no.1
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    • pp.32-55
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    • 1975

  • The ammonium salt of N-Nitrosophenylhydroxiamine, namely Cupferron, is a well-known analytical reagent which precipitates a great number of metal ions in acid medium. Various structures of electrode reduction for N-Nitrosophenylhydroxiamine have been suggested in acid and alkaline media by many researchers, but not in neutral medium. So the mechanism of electrode reaction of Cupferron was investigated by both chronopotentiometric and polarographic methods. It was estimated that the reduction of Cupferron occurs in a three-step mechanism through which a chemical step is interposed between two charge transfer, the ECE (charge transfer-chemical reaction-charge transfer) mechanism, over a range of neutral and alkaline media. The chemical reaction of the process was assumed to be acid-base catalyzed from the fact that kapp (over all rate constant) of chemical reaction is pH dependent.

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pH-Dependent Electrochemical Behavior of N-Monosubstituted-4,$4^{\prime}$-Bipyridinium Ions

  • Park, Joon-woo;Kim, Yuna;Lee, Chong-Mok
    • Bulletin of the Korean Chemical Society
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    • v.15 no.10
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    • pp.896-900
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    • 1994

  • The pH-dependent reduction behavior of N-monosubstituted-4,4'-bipyridinium ions ($RBPY^+: R=methyl(C_1)$; benzyl; n-octyl; n-dodecyl) has been investigated by electrochemical and spectroelectrochemical techniques. At acidic condition, $RBPY^+$ is protonated and the protonated species are reduced by two consecutive one-electron processes. The $2e^-$ reduced species undergoes a chemical reaction with $H^+$. The second-order rate constant $(k_H)$ of the homogeneous chemical process is $(3.7{\pm}0.3){\times}10^3M^{-1}s^{-1}$ for the two electron reduction product of $C_1BPY^+$. At high pH, the electrode reduction of $RBPY^+$ is one-step $2e^-$ transfer process with concomitant addition of $H^+$, which is confirmed by cyclic voltammetric study using a microdisk electrode.

  • https://doi.org/10.5012/bkcs.1994.15.10.896 인용 PDF

Development of cobalt encased in nitrogen and sulfur co-doped carbon nanotube for non-precious metal catalyst toward oxygen reduction reaction

  • Kim, Tae-Hyun;Sang, Byoung-In;Yi, Sung-Chul
    • Journal of Ceramic Processing Research
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    • v.19 no.6
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    • pp.499-503
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    • 2018

  • In this paper, cobalt embedded in nitrogen and sulfur co-doped carbon nanotubes (CoNSTs) were synthesized for oxygen reduction reaction (ORR) catalysts. The CoNSTs were prepared through a facile heat treatment method without any templates. Different amounts of the metal salt were employed to examine the physicochemical and electrochemical properties of the CoNSTs. The CoNSTs showed the bamboo-like tube morphology with the encased Co nanoparticles in the tubes. Through the x-ray photoelectron spectroscopy analysis, the catalysts exhibited different chemical states of the nitrogen and sulfur species. As a result, the CoNST performed high activity toward the ORR in an acidic condition with the onset potential of 0.863 V (vs. reversible hydrogen electrode). It was clearly demonstrated from the electrochemical characterizations that the quality of the nitrogen and sulfur species significantly influences the ORR activity rather than the total amount of the dopants.

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Effect of Cobalt Loading on the Performance and Stability of Oxygen Reduction and Evolution Reactions in Rechargeable Zinc-air Batteries

  • Sheraz Ahmed;Joongpyo Shim;Gyungse Park
    • Journal of the Korean Chemical Society
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    • v.68 no.2
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    • pp.87-92
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    • 2024

  • The commercialization of rechargeable metal-air batteries is extremely desirable but designing stable oxygen reduction reaction (ORR) catalysts with non-noble metal still has faced challenges to replace platinum-based catalysts. The nonnoble metal catalysts for ORR were prepared to improve the catalytic performance and stability by the thermal decomposition of ZIF-8 with optimum cobalt loading. The porous carbon was obtained by the calcination of ZIF-8 and different loading amounts of Co nanoparticles were anchored onto porous carbon forming a Co/PC catalyst. Co/PC composite shows a significant increase in the ORR value of current and stability (500 h) due to the good electronic conductive PCN support and optimum cobalt metal loading. The significantly improved catalytic performance is ascribed to the chemical structure, synergistic effects, porous carbon networks, and rich active sites. This method develops a new pathway for a highly active and advantageous catalyst for electrochemical devices.

  • https://doi.org/10.5012/jkcs.2024.68.2.87 인용 PDF HTML