• Carbon letters
• /
• 제24권
• /
• pp.1-9
• /
• 2017

We studied the basic properties and fabrication of reduced graphene oxide (rGO) prepared using eco-friendly reduction agents in the graphene solution process. Hydrazine is generally used to reduce graphene oxide (GO), which results in polluting emissions as well as fixed nitrogen functional groups on different defects in the graphene sheets. To replace hydrazine, we developed eco-friendly reduction agents with similar or better reducing properties, and selected of them for further analysis. In this study, GO layers were produced from graphite flakes using a modified Hummer's method, and rGO layers were reduced using hydrazine hydrate, L-ascorbic acid, and gluconic acid. We measured the particle sizes and the dispersion stabilities in the rGO dispersed solvents for the three agents and analyzed the structural, electrical, and optical properties of the rGO films. The results showed that the degree of reduction was in the order L-ascorbic acid ${\geq}$ hydrazine > glucose. GO reduced using L-ascorbic acid had a sheet resistance of $121k{\Omega}/sq$, while that reduced using gluconic acid showed worse electrical properties than the other two reduction agents. Therefore, L-ascorbic acid is the most suitable eco-friendly reduction agent that can be substituted for hydrazine.

• Biotechnology and Bioprocess Engineering:BBE
• /
• 제10권1호
• /
• pp.47-51
• /
• 2005

The bioelectrochemical reduction of nitrate in the presence of various mediators including methyl viologen and azure A was studied using a 3-electrode voltammetric system. The catalytic potential for the reduction of the mediators was observed in the reactor, which for methyl viologen and azure A were -0.74 V and -0.32 V, respectively, with respect to the potential of Ag/AgCl reference electrode. This potential was then applied to a working electrode to reduce each mediator for enzymatic nitrate reduction. Nitrite, the product of the reaction, was measured to observe the enzymatic nitrate reduction in the reaction media. Methyl viologen was observed as the most efficient mediator among those tested, while azure A showed the highest electron efficiency at the intrinsic reduction potential when the mediated enzyme reactions were carried out with the freely solubilized mediator. The electron transfer of azure A with respect to time was due to the adhesion of azure A to the hydrophilic surface during the reduction. In addition, the use of the adsorbed mediator on conductive activated carbon was proposed to inhibit the change in the electron transfer rate during the reaction by maintaining a constant mediator concentration and active surface area of the electrode. Azure A showed better than nitrite formation than methyl viologen when used with activated carbon.

• 한국재료학회지
• /
• 제29권10호
• /
• pp.592-602
• /
• 2019

Feasibility is investigated for reduction of chromium ore by Si sludge with mixed silicothermic and carbothermic reaction. The reduction behavior of chromium ore using Si sludge is investigated precisely to determine the effects of carbon addition, reaction time, and reaction temperature. The pellets are dropped into the furnace after temperature stabilized. As the amount of C addition increases, the amounts of CO and $CO_2$ gas generation increase. After the dropping of the pellets, the pellets are heated and the reaction starts at about 1,573 K or higher. The pellets maintain their shape until 10 min after the drop, and then melted. As the holding time increased, the size of the reduced metal particles increased. The chromium ore is rapidly reduced by the Si sludge, and the slag penetrated into the chromium ore and reduction progressed inside. As the reduction temperature increased, the reaction initiation time is shortened and the reaction fraction of the reduction reaction increased. As the reaction temperature increased, agglomeration of reduced ferrochrome metal is promoted.

• 분석과학
• /
• 제8권4호
• /
• pp.617-622
• /
• 1995

Electrocatalytic reduction of dioxygen has been investigated by cyclic voltammetry at glassy carbon electrode modified with new Co(II)-Schiff base complexes in aqueous solutions of various pH. The reduction potentials of dioxygen at chemically adsorbed electrodes show the dependence of pH between pH 4 and 14. The catalytic effect is large and the reaction occurs via two or four electron transfer in various pH solution.

• 한국표면공학회지
• /
• 제51권3호
• /
• pp.179-184
• /
• 2018

In this study, Ni and tungsten carbide (WC) nanoparticles are simultaneously synthesized with the mesoporous carbon nanoparticles (CNP) using a solution plasma processing (SPP) in the benzene. The Ni and WC nanoparticles were formed through the sputtering effect of electrodes during discharge, and mean time CNP were formed through reduction reaction. TEM observation showed that loaded Ni and WC nanoparticles were evenly dispersed on the CNP. The results of electrochemical analysis demonstrated that an introduction of Ni nanoparticles promoted to improve catalytic activity for oxygen reduction reaction (ORR). Moreover, Ni-WC/CNP lead to fast electron transfer process compared to that of WC/CNP. Therefore, the inexpensive Ni-WC/CNP might be a promising as catalytic material for cathodes in fuel cell applications.

• Bulletin of the Korean Chemical Society
• /
• 제16권5호
• /
• pp.392-397
• /
• 1995

o-Phenylenediamine (o-PD) was electropolymerized on glassy carbon electrodes under a potential cycling condition. The resulting polymer films mediated electrons for the reduction of molecular oxygen at pH=1.0. It was found from the RDE, RRDE, and cyclic voltammetry experiments that the modified electrodes reduce oxygen to hydrogen peroxide at about 300 mV lower potential than the bare glassy carbon electrode. The polymer film consisted of more than two components. Among those, only one component was active in oxygen reduction, which was formed mainly in the earlier stage of the electropolymerization. 2,3-Diaminophenazine, a cyclic dimer of o-PD, was also active in the oxygen reduction reaction, from which it was suggested that the active polymeric component has a structural unit similar to the cyclic dimer. Finally, the electropolymerization mechanism for the formation of the active and inactive components has been proposed.

• Bulletin of the Korean Chemical Society
• /
• 제15권7호
• /
• pp.563-567
• /
• 1994

The electroreduction of dioxygen at glassy carbon electrodes with irreversible self-assembly of N-hexadecyl-N'-methyl viologen $(C_{16}VC_1)$ proceeds at potentials more positive than those where the reduction occurs at bare electrodes. The electrocatalyzed reduction takes place at potentials well ahead of those where the catalyst is reduced in the absence of dioxygen and the limiting currents observed at rotating disk electrodes did not deviate from the thoretical Levich line up to 6400 rpm, indicating that the electrocatalysis is extremely rapid. The rate constant for the heterogeneous reaction between $C_{16}V^+C_1$ immobilized on the electrode surface and $O_2$ in solution was estimated to be ca. $10^8\;M^{-1}s^{-1}$. The half-wave potential of dioxygen reduction was independent of solution pH.

• Bulletin of the Korean Chemical Society
• /
• 제17권3호
• /
• pp.223-227
• /
• 1996

Catalytic effects of transition metal (Co2+, Ni2+) complexes of N,N-bis(salicylaldehyde)-o-phenylenediimine (SOPD), N,N-bis(salicylaldehyde)-m-phenylenediimine (SMPD), and N,N-bis(salicylaldehyde)-p-phenylenediimine (SPPD), on the reduction of thionyl chloride at glassy carbon electrode, are evaluated by determining the kinetic parameters with cyclic voltammetric technique. The charge transfer process for the reduction of thionyl chloride is strongly affected by the concentration of the catalysts. Some quadridentate Schiff base-M(Ⅱ) complexes show sizable catalytic activities for the reduction of thionyl chloride. Catalytic effects of [M(Ⅱ)(SOPD)] complexes are slightly larger compared to [M(Ⅱ)2(SMPD)2] and [M(Ⅱ)2(SPPD)2] complexes. On those electrodes deposited with the catalysts, the observed exchange rate constants (ko) are in the range of 0.89-2.28 × 10-7 cm/s, while it is 1.24 × 10-7 cm/s on the bare glassy carbon electrode.

• 자원환경지질
• /
• 제54권6호
• /
• pp.733-741
• /
• 2021

전세계적으로 2015년 파리기후협약에서 정한 목표에 따라 2050년까지 탄소중립을 위하여 각 국가는 감축목표를 수립 및 선언하고, "장기 저탄소 발전전략" (Long-term low greenhouse gas Emission Development Strategies, LEDS)을 수립, 감축 목표 설정을 위한 로드맵 등을 발표하고 있다. 국제사회의 탄소중립사회 전환 가속화에 따라 2020년말까지 128개국이 탄소중립을 선언하였으며, G20 회원국을 중심으로 지속적으로 탄소중립선언이 확대되고 있다. 우리나라도 2020년 12월 탄소중립의 능동적 대응을 통해 탄소중립과 경제성장, 국민 삶의 질 향상을 동시 달성하는 기반 마련을 위한 "2050 탄소중립 추진전략"을 발표하였고, 이를 위한 정책과제를 단계적으로 추진하고 있다. 우리나라에서 온실가스 감축을 위하여 시행되고 있는 온실가스에너지 목표관리제 및 온실가스 배출권거래제 상쇄제도 등 의무감축제도의 영역에서 벗어나 있어 종합적인 탄소관리는 미흡하며, 현재 광해방지사업으로 인한 이산화탄소배출량을 정량화한 사례는 없다. 따라서, 본 연구에서는 전세계적인 탄소중립의 관심과 정부 정책 기조에 따라 탄소 중립 실현을 위해서 한국광해광업공단의 주 업무인 광해방지사업에 대하여 국내외 탄소배출량 산정 방법으로 제시된 표준방법을 검토하고, 광해방지사업에 적합한 탄소배출량 산정 방법을 제시하고자 하였다.

• 한국기후변화학회지
• /
• 제8권1호
• /
• pp.73-80
• /
• 2017

This study sees the past, present and future of the international carbon market. It is expected that it is not until 2020 and beyond before the international carbon market is settled by international consensus, and it is too early to picture the international carbon market at this point. Instead, this study focuses on analyzing the content of Article 6 of the Paris Convention, being fully aware of the uncertainties surrounding the international carbon market and can only be a step in determining the future of the international carbon market. In the future, the international negotiations will be under fierce competition of countries, each of which aims to make their advantageous system or mechanism recognized internationally Therefore, it is necessary for Korea to devise a system that can maximize the national interest and try to be recognized in the international society. To accomplish this, the following tasks are required at the present stage. First, we need to include the basic directions for the reduction using the international carbon market in the preparation of the roadmap for GHG reduction in Korea. Based on the directions presented in the roadmap for reducing GHG emissions, Korea should set up a government-wide plan on the international carbon market. In addition, a long-term TF should be formed to enact such plans in the international community. The international carbon market is an issue that several professional fields overlap, and it is indeed difficult to pursue by a single ministry. Therefore, it is necessary to create and strengthen the TF that can cope immediately with the international movement.