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열산화법으로 생성된 TiO₂ 중간보호층이 Ti/RuO₂-PdO-TiO₂ 전극의 염소발생 효율 및 내구성에 미치는 영향
박다정(Da Jung Park),최승목(Sung Mook Choi),이규환(Kyu Hwan Lee) 한국표면공학회 2018 한국표면공학회지 Vol.51 No.4
Not only efficiency of chlorine evolution reaction (CER) but also durability namely service life is very important property in dimensional stable anode for Ballast Water Management System (BWMS) for marine ships. Many researchers have been focused on improving efficiency of CER by controlling composition, phase and surface area for a long time, but the efforts to increase durability was relatively small. In this study, we have investigated the effect of TiO₂ protective interlayers on efficiency and durability of DSA electrodes. TiO₂ protective interlayers were prepared by thermal oxidation at 500, 600 and 700℃ on Ti substrate. And then the DSA electrodes consisting of Ti/RuO₂-PdO-TiO₂ were prepared by thermal decomposition method on TiO₂ interlayers. The efficiencies of CER of DSA electrodes without TiO₂ interlayer and with TiO₂ interlayer grown at 500, 600 and 700℃ were 94.19, 94.45, 84.60 and 76.75% respectively. On the otherhand, durabilities were 30, 55, 90 and 65 hours respectively. In terms of industrial aspect, the performance of DSA is considered high efficiency and durability which can correspond to total production of chlorine. If we considered the performance index of DSA as the product of efficiency and durability, performance indices could be recalculated as 28.26, 50.85, 76.14 and 49.89 respectively. As the thermal oxidation temperature increasing, life time were increased remarkerbly, while efficiency of CER was decreased slightly. As a result, DSA electrode with TiO₂ interlayer grown at 600oC has shown about 2.7 times performace of original DSA electrode without TiO₂ interlayer.
일산화탄소 산화를 위한 PtRu/C 시리즈 촉매의 합성 및 특성 연구
이선화(Seonhwa Lee),최승목(Sung Mook Choi),김원배(Won Bae Kim) 한국청정기술학회 2012 청정기술 Vol.18 No.4
백금(Pt)과 루테늄(Ru)의 조성비가 일산화탄소(CO) 산화반응에 미치는 영향을 조사하고자 탄소를 지지체(support)로 사용한 20 wt% 백금과 백금-루테늄 시리즈 촉매(Pt : Ru = 7 : 3, 5 : 5, 3 : 7)를 콜로이드 방법(colloidal method)으로 합성하였다. 다양한 물리?화학적 분석장비인 투과전자현미경(transmission electron microscopy, TEM)과 X-선 회절(X-ray diffraction, XRD), 에너지 분산형 X-선 분석기(energy dispersive X-ray spectroscopy, EDS)를 이용하여 구조?화학적 특성을 분석하고, X-선 광전자 분광법(X-ray photoelectron spectroscopy, XPS)을 통해 전자적 특성 변화를 확인하였다. 더불어 일산화탄소 벗김 전압전류실험(CO stripping voltammetry)을 이용하여 전기화학적 거동을 분석하였다. 합성된 촉매들 중 Pt5Ru5/C가 가장 낮은 개시 전위(vs. Ag/AgCl)와 가장 큰 일산화탄소의 전기화학적 활성화 표면적(CO EAS) 값을 나타냈으며 이를 통해 Pt5Ru5/C이 일산화탄소의 전기화학적 산화반응에 있어 가장 효과적인 촉매임을 확인하였다. Pt5Ru5/C의 격자상수 변화를 통한 구조적 특성변화 및 백금 d-밴드의 페르미 레벨 변화를 통한 전자적 특성변화 그리고 이작용기(bifunctional)의 효과가 일산화탄소의 전기화학적 산화반응에 대한 활성을 증진시켰다고 사료된다. The electrocatalytic oxidation of CO was studied using carbon-supported 20 wt% PtRu (PtRu/C) catalysts, which were prepared with different Pt : Ru atomic ratios from 7 : 3 to 3 : 7 using a colloidal method combined with a freeze-drying procedure. The bimetallic PtRu/C catalysts were characterized by various physicochemical analyses, including X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). CO stripping voltammetry measurements indicated that the addition of Ru with a Pt catalyst significantly improved the electrocatalytic activity for CO electrooxidation. Among the tested catalysts, the Pt5Ru5/C catalyst had the lowest onset potential (vs.Ag/AgCl) and the largest CO EAS. Structural modification via lattice parameter change and electronic modification in the unfilled d band states for Pt atoms may facilitate the electrooxidation of CO.
수소발생반응을 위한 Ni₄Cr 나노 섬유 전기화학 촉매 합성 및 특성 분석
이정훈(Jeong Hun Lee),장명제(Myeong Je Jang),박유세(Yoo Sei Park),최승목(Sung Mook Choi),김양도(Yang Do Kim),이규환(Kyu Hwan Lee) 한국표면공학회 2017 한국표면공학회지 Vol.50 No.5
Hydrogen evolution reaction(HER) was studied over Ni₄Cr nanofibers(NFs) prepared by electrospinning method and oxidation/reduction heat treatment for alkaline water electrolysis. The physicochemical and electrochemical properties such as average diameter, lattice parameter, HER activity of synthesized Ni₄Cr NFs could be modified by proper electrospinning process condition and reduction temperature. It was shown that Ni₄Cr NFs had average diameter from 151 to 273 nm. Also, it exhibited the overpotential between 0.419 V and 0.526 V at 1 mA/㎠ and Tafel slope of -334.75 mV to -444.55 mV per decade in 1 M KOH solution. These results indicate that Ni₄Cr NFs with reduction heat treatment at 600 oC show thinnest diameter and highest HER activity among the other catalysts.
음이온 교환막 알칼리 수전해를 위한 운전 조건 및 구성요소의 최적화
장명제(Myeong Je Jang),원미소(Mi So Won),이규환(Kyu Hwan Lee),최승목(Sung Mook Choi) 한국표면공학회 2016 한국표면공학회지 Vol.49 No.2
The hydrogen has been recognized as a clean, nonpolluting and unlimited energy source that can solve fossil fuel depletion and environmental pollution problems at the same time. Water electrolysis has been the most attractive technology in a way to produce hydrogen because it does not emit any pollutants compared to other method such as natural gas steam reforming and coal gasification etc. In order to improve efficiency and durability of the water electrolysis, comprehensive studies for highly active and stable electrocatalysts have been performed. The platinum group metal (PGM; Pt, Ru, Pd, Rh, etc.) electrocatalysts indicated a higher activity and stability compared with other transition metals in harsh condition such as acid solution. It is necessary to develop inexpensive non-noble metal catalysts such as transition metal oxides because the PGM catalysts is expensive materials with insufficient it’s reserves. The optimization of operating parameter and the components is also important factor to develop an efficient water electrolysis cell. In this study, we optimized the operating parameter and components such as the type of AEM and density of gas diffusion layer (GDL) and the temperature/concentration of the electrolyte solution for the anion exchange membrane water electrolysis cell (AEMWEC) with the transition metal oxide alloy anode and cathode electrocatalysts. The maximum current density was 345.8 mA/c㎠ with parameter and component optimization.
산소발생반응을 위한 CuCo₂O₄ 나노섬유 전기화학 촉매 합성 및 특성 분석
원미소(Mi So Won),장명제(Myeong-Je Jang),이규환(Kyu Hwan Lee),김양도(Yang Do Kim),최승목(Sung Mook Choi) 한국표면공학회 2016 한국표면공학회지 Vol.49 No.6
The non-noble 1D nanofibers(NFs) prepared by electrospinning and calcination method were used as oxygen evolution reaction (OER) electrocatalyst for water electrolysis. The electrospinning process and rate of solution composition was optimized to prepare uniform and non-beaded PVP polymer electrospun NFs. The diameter and morphology of PVP NFs changed in accordance with the viscosity and ion conductivity. The clean metal precursor contained electrospun fibers were synthesized via the optimized electrospinning process and solution composition. The calcined CuCo₂O₄ NFs catalyst showed higher activity and long-term cycle stability for OER compared with other Co₃O₄, NiCo₂O NF catalysts. Furthermore, the CuCo₂O₄ NFs maintained the OER activity during long-term cycle test compared with commercial CuCo₂O₄ nanoparticle catalyst due to unique physicochemical and electrochemical properties by1D nanostructure.