• Bulletin of the Korean Chemical Society
• /
• 제35권3호
• /
• pp.839-844
• /
• 2014

The gas-phase radical-radical reaction $O(^3P)$ + $C_2H_5$ (ethyl) ${\rightarrow}$ $H(^2S)$ + $CH_3CHO$(acetaldehyde) was investigated by applying a combination of vacuum-ultraviolet laser-induced fluorescence spectroscopy in a crossed beam configuration and ab initio calculations. The two radical reactants $O(^3P)$ and $C_2H_5$ were respectively produced by photolysis of $NO_2$ and supersonic flash pyrolysis of the synthesized precursor azoethane. Doppler profile analysis of the nascent H-atom products in the Lyman-${\alpha}$ region revealed that the average translational energy of the products and the average fraction of the total available energy released as translational energy were $5.01{\pm}0.72kcalmol^{-1}$ and 6.1%, respectively. The empirical data combined with CBS-QB3 level ab initio theory and statistical calculations demonstrated that the title exchange reaction is a major channel and proceeds via an addition-elimination mechanism through the formation of a short-lived, dynamical addition complex on the doublet potential energy surface. On the basis of systematic comparison with several exchange reactions of hydrocarbon radicals, the observed small kinetic energy release can be explained in terms of the loose transition state with a product-like geometry and a small reverse activation barrier along the reaction coordinate.

• 한국수소및신에너지학회논문집
• /
• 제24권4호
• /
• pp.288-294
• /
• 2013

This gas analysis data come from the hydrogen which is produced by proton exchange membrane. Main impurities of hydrogen are methane, oxygen, nitrogen, carbon monoxide, and carbon dioxide. The concentration of impurities is ranged between 0.0191 to $315{\mu}mol/mol$ for each impurity. Methane contamination is believed from the electrode reaction between carbon doped electrode and produced hydrogen. Nitrogen contamination should take place the sampling process error, not from PEM hydrogen Production system.

• 한국표면공학회지
• /
• 제56권6호
• /
• pp.412-419
• /
• 2023

Anion exchange membrane electrolysis is considered a promising next-generation hydrogen production technology that can produce low-cost, clean hydrogen. However, anion exchange membrane electrolysis technology is in its early stages of development and requires intensive research on electrodes, which are a key component of the catalyst-system interface. In this study, we optimized the pressure conditions of the hot-pressing process to manufacture cobalt oxide electrodes for the development of a high uniformity and high adhesion electrode production process for the oxygen evolution reaction. As the pressure increased, the reduction of pores within the electrode and increased densification of catalytic particles led to the formation of a uniform electrode surface. The cobalt oxide electrode optimized for pressure conditions exhibited improved catalytic activity and durability. The optimized electrode was used as the anode in an AEMWE single cell, exhibiting a current density of 1.53 A cm^-2 at a cell voltage of 1.85 V. In a durability test conducted for 100 h at a constant current density of 500 mA cm^-2, it demonstrated excellent durability with a low degradation rate of 15.9 mV kh^-1, maintaining 99% of its initial performance.

• 한국수소및신에너지학회논문집
• /
• 제27권4호
• /
• pp.335-340
• /
• 2016

Hydrogen production through proton exchange membrane water electrolysis (PEMWE) is expeditiously receiving international attention for renewable energy sources as well as energy storage system applications due to its environmentally friendly uses. A series of $Ir_{0.2}Ru_{0.8}O_2$ $Ir_{0.5}Ru_{0.8}O_2$ & $IrO_2$ catalysts were synthesized and electrochemically evaluated by using linear sweep voltammetry (LSV) technique. Furthermore, the PEMWE performances of full cells were evaluated by recording I-V Curves. The developed PEMWE stack was also operated in combination with a proton exchange membrane fuel cell (PEMFC) to demonstrate the discrete regenerative fuel cell (DRFC) performances. Produced hydrogen and oxygen from PEMWE were used as a fuel to operate PEMFC to establish a DRFC system.

• 한국수소및신에너지학회논문집
• /
• 제25권4호
• /
• pp.378-385
• /
• 2014

In this research, we investigate electrical performance and electrochemical properties of graphene supported Pt (Pt/G) and PtM (M = Ni and Y) alloy catalysts (PtM/Gs) that are synthesized by modified polyol method. With the PtM/Gs that are adopted for oxygen reduction reaction (ORR) as cathode of proton exchange membrane fuel cells (PEMFCs), their catalytic activity and ORR performance and electrical performance are estimated and compared with one another. Their particle size, particle distribution and electrochemically active surface (EAS) area are measured by TEM and cyclic voltammetry (CV), respectively. On the other hand, regarding ORR activity and electrical performance of the catalysts, (i) linear sweeping voltammetry by rotating disk electrode and rotating ring-disk electrode and (ii) PEMFC single cell tests are used. The TEM and CV measurements demonstrate particle size and EAS of PtM/Gs are compatible with those of Pt/G. In case of PtNi/G, its half-wave potential, kinetic current density, transferred electron number per oxygen molecule and $H_2O_2$ production % are excellent. Based on data obtained by half-cell test, when PEMFC singlecell tests are carried out, current density measured at 0.6V and maximum power density of the PEMFC single cell employing PtNi/G are better than those employing Pt/G. Conclusively, PtNi/Gs synthesized by modified polyol shows better ORR catalytic activity and PEMFC performance than other catalysts.

• Journal of Mechanical Science and Technology
• /
• 제17권9호
• /
• pp.1358-1370
• /
• 2003

The effects of anode, cathode, and cooling channels for a Proton Exchange Membrane Fuel Cell (PEMFC) on flow fields have been investigated numerically. Continuous open-faced fluid flow channels formed in the surface of the bipolar plates traverse the central area of the plate surface in a plurality of passes such as a serpentine manner. The pressure distributions and velocity profiles of the hydrogen, air and water channels on bipolar plates of the PEMFC are analyzed using a two-dimensional simulation. The conservation equations of mass, momentum, and energy in the three-dimensional flow solver are modified to include electro-chemical characteristics of the fuel cell. In our three-dimensional numerical simulations, the operation of electro-chemical in Membrane Electrolyte Assembly (MEA) is assumed to be steady-state, involving multi-species. Supplied gases are consumed by chemical reaction. The distributions of oxygen and hydrogen concentration with constant humidity are calculated. The concentration of hydrogen is the highest at the center region of the active area, while the concentration of oxygen is the highest at the inlet region. The flow and thermal profiles are evaluated to determine the flow patterns of gas supplied and cooling plates for an optimal fuel cell stack design.

• 한국표면공학회지
• /
• 제55권3호
• /
• pp.180-186
• /
• 2022

The production of hydrogen via water electrolysis (i.e., green hydrogen) using renewable energy is key to the development of a sustainable society. However, most current electrocatalysts are based on expensive precious metals and require the use of highly purified water in the electrolyte. We demonstrated the preparation of a non-precious metal catalyst based on CuCo₂O₄ (CCO) via simple electrodeposition. Further, an optimization process for electrodeposition potential, solution concentration and electrodeposition method was develop for a catalyst-substrate integrated electrode, which indicated the highly electrocatalytic performance of the material in electrochemical tests and when applied to an anion exchange membrane water electrolyzer.

• 전기화학회지
• /
• 제25권2호
• /
• pp.69-80
• /
• 2022

고순도 수소생산을 위한 음이온 교환막 수전해는 양성자 교환막 수전해 시스템에서 사용되는 기존 귀금속 촉매 대신 저렴한 비귀금속 기반 촉매를 사용하여 차세대 녹색 수소 생산 기술로 많은 관심을 받고 있다. 하지만 음이온 교환막 수전해 기술은 개발 초기 단계이기 때문에 음이온 교환막 수전해의 핵심 요소인 음이온 교환막, 이오노머, 전극지지체 및 촉매에 관한 연구 수행이 필요하다. 그 중, 현재 촉매 분야에서 진행되고 있는 연구들은 기개발된 알칼리용 반쪽전지 촉매를 음이온 교환막 시스템에 적용하는 방향의 연구가 진행되고 있으며 적용된 촉매는 낮은 활성도와 내구성의 문제점을 가진다. 이에 본 총설은 알칼리성 매질에서 비귀금속 기반 촉매를 사용하여 산소발생반응 및 수소발생반응을 촉진시킨 촉매 합성 기술을 제시하였다.

• 한국표면공학회지
• /
• 제56권6호
• /
• pp.427-436
• /
• 2023

In the industry, it is recognized that human activities significantly lead to a large amount of wastewater, mainly due to the increased use of water and energy. As a result, the growing field of wastewater resource technology is getting more attention. The common technology for hydrogen production, water electrolysis, requires purified water, leading to the need for desalination and reprocessing. However, producing hydrogen directly from wastewater could be a more cost-effective option compared to traditional methods. To achieve this, a series of first-principle computational simulations were conducted to assess how waste nutrient ions affect standard electrolysis catalysts. This study focused on understanding the adsorption mechanisms of byproducts related to the oxygen evolution reaction (OER) in anion exchange membrane (AEM) electrolysis, using Co₃O₄ as a typical non-precious metal catalyst. At the same time, efforts were made to develop a comprehensive free energy prediction model for more accurate predictions of OER results.

• 멤브레인
• /
• 제32권5호
• /
• pp.283-291
• /
• 2022

재생에너지의 보급과 기후변화를 대응하기 위한 해결책으로 수소에너지에 대한 관심이 늘어나고 있다. 수소는 미이용 전력을 대용량 장주기로 저장하기에 가장 적합한 수단이며 이러한 수소를 생산하는 기술 중 수전해는 물에 전기에너지를 인가하여 수소를 생산하는 친환경적 수소생산 기술로 알려져 있다. 수전해의 구성 요소 중 분리막은 음극과 양극을 물리적으로 분리할 뿐만 아니라 생성되는 수소와 산소의 섞임 현상을 방지하며 이온의 전달을 가능하게 하는 복합적인 역할을 수행한다. 특히 기존의 수전해 기술들의 단점을 보완할 수 있는 차세대 음이온 교환막 수전해에서의 핵심은 우수한 음이온 교환막을 확보하는 것이다. 높은 이온 전도성과 알칼리 환경에서 우수한 내구성을 동시에 가지려는 많은 연구들이 진행되고 있으며 다양한 소재에 대한 탐색이 이루어지고 있다. 본 총설에서는 상용 블록 공중합체인 Polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS)를 기반으로 하는 음이온 교환막에 대한 연구에 대해 살펴보며 최신 연구 동향과 앞으로 나아가야할 점에 대해 논하고자 한다.