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Synthesis and Characterization of Silver Coated Electrospun Cobalt Nanotubes and Their Electrocatalytic Activity

Synthesis and Characterization of Silver Coated Electrospun Cobalt Nanotubes and Their Electrocatalytic Activity
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대학원 화학·나노과학과
이화여자대학교 대학원
Recently much attention has been paid to one-dimensional (1D)nanostructures. One of the most promising methods to prepare 1D nanostructures is electrospinning. Electrospinning has gained much attention due to not only its diversity of the electrospinning materials but also its simplicity. In this study, Co nanotubes were prepared by electrospinning, followed by calcination and reduction. Then, AgCo nanotubes were synthesized through the galvanic replacement reactions (GRR) between as prepared Co nanotubes and Ag precursor in aqueous solution and characterized electrochemically. In order to optimize the synthetic condition for AgCo nanotubes, we controlled the reduction time of Co3O4 nanotubes and the GRR time between Co nanotubes and Ag precursor. The morphologies and compositions of the prepared AgCo nanotubes were characterized by field-emission scanning electron microscopy (FE-SEM), energydispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). For the electrochemical characterization, three-electrode cell was used with a glassy carbon electrode loaded with the synthesized AgCo nanotubes as the working electrode and a saturated calomel electrode (SCE) as the reference electrode, and a coiled platinum wire as the counter electrode. Electrochemical activities of these nanomaterials for oxygen reduction reaction (ORR) were characterized with rotating disk electrode (RDE) voltammetry in 0.1 M NaOH aqueous solution. The ORR catalytic activity of AgCo nanotubes was compared with the those of Ag nanowires and Co nanotubes.;최근 일차원적 나노구조 합성 및 활성에 대한 관심이 높아지고 있는데, 그 중 전기방사는 일차원 나노구조를 간단하게 합성할 수 있을 뿐만 아니라 소재와 구성의 다양성 때문에 큰 관심을 이끌어내고 있다. 이 논문에서는 전기방사의 방법을 이용하여 합성한 나노튜브 형태의 코발트옥사이드에 수소 기체를 흘려주며 코발트 나노튜브로 환원시켰다. 코발트 나노튜브와 은 전구체의 자발적인 갈바닉 치환 반응(Galvanic Replacement Reaction)을 통해 속이 빈 형태의 실버-코발트 나노튜브(AgCo nanotube)를 합성하였다. 합성 조건을 최적화하기 위해서 환원 시간과 갈바닉 치환 반응의 시간을 조절하면서 실험하였다. 물질의 구조와 구성은 전자주사현미경 (scanning electron microscopy), 에너지-분산 X-선 분광법 (Energy-dispersive X-ray spectroscopy, EDS), X선 회절 (X-ray diffraction), X선 광전자 분광법 (X-ray photoelectron spectroscopy)을 사용하여 확인하였다. 합성한 물질들에 대해 0.1 M NaOH 용액에서 원판회전전극(rotating disk electrode, RDE)을 이용하여 산소 환원 반응 (oxygen reduction reaction, ORR)에 대한 촉매 활성을 연구하였다.
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