Photocatalytically splitting water into hydrogen upon semiconductors has tremendous potential for alleviating environmental and energy crisis issues. There is increasing attention on improving solar light utilization and engineering photogenerated charge transfer of TiO2 photocatalyst because it has advantages of low cost, non-toxicity, and high chemical stability. Herein, oxygen vacancies and cocatalysts (Cu and MoS2) were simultaneously introduced into TiO2 nanoparticles from protonic titanate by a one-pot solvothermal method. The composition and structure characterization confirmed that the pristine TiO2 nanoparticle was rich in oxygen vacancies. The photocatalytic performances of the composites were evaluated by solar-tohydrogen evolution test. The results revealed that both Cu-TiO2 and MoS2- TiO2 could improve the photocatalytic hydrogen evolution ability. Among them, 0.8% Cu-TiO2 showed the best hydrogen evolution rate of 7245.01 μmol·g−1·h−1, which was 3.57 and 1.34 times of 1.25% MoS2- TiO2 (2726.22 μmol·g−1·h−1) and pristine TiO2 material (2028.46 μmol·g−1·h−1), respectively. These two kinds of composites also had good stability for hydrogen evolution. Combined with the results of photocurrent density and electrochemical impedance spectra, the incorporation of oxygen vacancies and cocatalysts (Cu and MoS2) could not only enhance the light-harvesting of TiO2 but also improve the separation and transfer capabilities of light-induced charge carriers, thus promoting water splitting to hydrogen.

본 연구에서는 중공사형 이산화탄소 분리막 모듈을 사용하여 수소개질기 배가스로부터 이산화탄소 포집을 목적 으로 한 분리막 공정 최적화 연구를 진행하였다. 랩스케일의 소형 분리막 모듈을 사용하여 혼합기체를 대상으로 이산화탄소 순도 90% 및 회수율 90%을 달성하는 2단 공정 조건을 도출하였다. 막 면적이 정해진 모듈의 분리막 공정에서는 스테이지-컷, 주입부 및 투과부 압력에 따라서 포집 순도 및 회수율이 모두 다르게 나타나기 때문에 운전 조건에 대한 최적화가 필수적이 다. 본 연구에서는 다양한 운전 조건에서 1단 분리막에서 보이는 공정 포집 효율의 한계를 확인하고, 높은 순도와 회수율을 동시에 달성하기 위한 2단 회수 공정을 최적화하였다.

The thermocatalytic decomposition of methane is a promising method for hydrogen production. To determine the cause of carbonaceous catalyst deactivation and to produce high-value carbon, methane decomposition behavior and deactivated catalysts were analyzed. The surface properties and crystallinity of a commercial activated carbon material, MSP20, used as a methane decomposition catalyst, varied with the reaction time at a reaction temperature of 900 °C. During the initial reaction, MSP20 provided a methane conversion of ≥ 50%; however, the catalyst exhibited rapid deactivation as crystalline carbon grew at surface defects; after 15 min of reaction, approximately 33% methane conversion was maintained. With increasing reaction time, the specific surface area of the catalyst decreased, whereas crystallinity increased. The R-square value of the conversion–crystallinity relationship was significantly higher than that of the conversion–specific surface area relationship; however, neither profile was linear. The activity of the activated carbon catalyst for methane decomposition is mainly determined by the complex actions of the specific surface area and defect sites. The activity was maintained after an initial sharp decline caused by the continuous growth of crystalline carbon product. This study presents the application of carbonaceous catalysts for the decomposition reaction of methane to form COx- free hydrogen, while simultaneously yielding porous carbon materials with an improved electrical conductivity.

Ammonia is a potential fuel for producing and storing hydrogen, but its usage is constrained by the high cost of the noble metal catalysts to decompose NH3. Utilizing non-precious catalysts to decompose ammonia increases its potential for hydrogen production. In this study, carborundum (SiC)-supported cobalt catalysts were prepared by impregnating Co3O4 nanoparticles (NPs) on SiC support. The catalysts were characterized by high-resolution transmission electron microscope, X-ray photoelectron spectroscopy, temperature programmed reduction, etc. The results show that the large specific surface area of SiC can introduce highly distributed Co3O4 NPs onto the surface. The amount of Co in the catalysts has a significant effect on the catalyst structure, particle size and catalytic performances. Due to the interaction of cobalt species with SiC, the 25Co/SiC catalyst provided the optimal ammonia conversion of 73.2% with a space velocity of 30,000 mL gcat −1 h− 1 at 550 °C, corresponding to the hydrogen production rate of 24.6 mmol H2 gcat −1 min− 1. This research presents an opportunity to develop highly active and cost-effective catalysts for hydrogen production via NH3 decomposition.

The International Atomic Energy Agency recommends the deep geological disposal system as one of the disposal methods for high-level radioactive waste (HLW), such as spent nuclear fuel. The deep geological disposal system disposes of HLW in a deep and stable geological formation to isolate the HLW from the human biosphere and restrict the inflow of radionuclides into the ecosystem. It mainly consists of an engineered barrier and a natural barrier. Safety evaluation using a numerical model has been performed primarily to evaluate the buffer’s long-term stability. However, although the gas generation rate input for long-term stability evaluation is the critical factor that has the most significant influence on the long-term hydraulic-mechanical behavior of the buffer, in-depth research and experimental data are lacking. In this study, the gas generation rate on the interface between the disposal canister and the buffer material, a component of the engineered barrier, was mainly studied. Gas can be generated between the disposal canister and the buffer material due to various causes such as anaerobic corrosion of the disposal canister metal, organic matter decomposition, radiation decomposition, and steam generation due to high temperature. The generation of gas in such a disposal environment increases the pore gas pressure in the buffer and causes internal cracks. The occurred cracks increase the intrinsic permeability of the buffer, which leads to a decrease in the primary performance of the buffer. For this reason, it is essential to apply the appropriate gas generation rate according to the disposal condition and buffer material for accurate long-term stability analysis. Therefore, the theoretical models regarding the estimation of gas generation were summarized through a literature study. The amount of gas generated was estimated according to the disposal environment and material of the disposal canister. It is expected that estimated values might be used to estimate the long-term stability analysis of buffer performance according to the disposal condition.

Odor is a type of sensory pollution that can stimulate the human sense of smell when it occurs, causing discomfort and making it difficult to create a pleasant environment. For this reason, there is a high possibility of complaints regarding odors if odors occur in pigsties near residential properties, and the number of such complaints is also increasing. In addition, odors emanating from pigsties around military installations can cause physical and psychological harm, not only to the soldiers living in these type of facilities but also to the families belonging to military personnel living there as well. Because the concentration of odors varies due to diverse factors such as temperature, humidity, wind direction, wind speed, and interaction between causative materials, predicting odors based on only one factor is not proper or appropriate. Therefore, in this work, we sought to construct models that are based on several regression techniques of machine learning using data collected in field. And we selected and utilized the model that has the highest-accuracy in order to notify and warn residents of odors in advance. In this work, 3672 data items were used to train and test the model. The several machine learning algorithms to build the models are polynomial regression, ridge regression, K-nearest neighbor regression (KNN Regression), and random forest. Comparing the performance of models based on each algorithm, the study found that KNN Regression was the most suitable model, and the result obtained from KNN regression was significant.

본 총설은 분리막기술이 적용된 수소생산에 대한 개론으로, 특히, 암모니아를 수소운반체로 이용하는 수소생산에 대한 연구결과를 중점적으로 서술하였다. 암모니아를 수소운반체로 적용한 수소생산은 추가적인 탄소생성이 없다는 점 외에 여러 측면에 있어 이점이 있다. 많은 연구들이 고순도 수소 분리 및 생산을 위한 분리막 개발을 위해 진행되고 있으며, 이들 중 팔라듐을 기본으로 한 분리막(예를 들어, 다공성 세라믹 또는 다공성 금속 지지체와 팔라듐 합금의 얇은 선택층으로 이루어진 분리막)에 대한 연구가 활발하다. 반면에, 효율적인 암모니아 분해를 위해서는 주로 루테늄 촉매가 적용되고 있으며, 루테늄과 지지체 및 촉진제로 이루어진 루테늄에 기반을 둔 촉매에 대한 연구발표가 다수 존재한다. 수소생산을 위한 분리막 반응기 형태로는 충전층, 유동층, 그리고 마이크로반응기 등이 있으며, 이들의 최적화 및 원활한 물질전달 연구는 현재진행형 이다. 또한, 높은 암모니아 분해율, 고순도 수소생산 및 높은 수소생산율을 얻기 위해 분리막과 촉매의 다양한 조합에 대한 연구 및 분리막과 촉매의 역할을 동시에 구현할 수 있는 분리막에 대한 연구가 발표되고 있다.

수소를 연료로 사용하는 PEMFC는 고효율⋅출력밀도를 나타내며, 짧은 시동시간, 우수한 응답특성에 따라 현지설치형 발전기술로 사용되며, 이를 위한 고효율 연료처리장치가 필수적이다. SMR반응은 연료당 고회수율을 때문에 경제성이 우수하며, 전환율 확보를 위해 700°C, 20 bar 이상의 운전조건에서 수행되며, WGS, PSA의 후단공정을 통해 수소를 생산한다. 분리막 개질기를 이용한 SMR반응은 분리막이 수소를 제거함에 따라 반응효율 증진, 공정온도 저감, 후단공정 배제를 할 수 있어 공정구성 및 경제성이 우수하다. 본 연구에서는 팔라듐분리막 개질기를 사용하여 550°C, 5 bar에서 SMR반응을 통해 수소를 생산하였으며, 개질된 가스의 CO 농도를 최소화하여 고온 PEMFC용 연료처리장치를 개발하였다.

수소는 산업용 전력생산, 자동차용 연료 등을 위한 대체가능한 에너지 담체로 인식되고 있다. 미래 저탄소 에너지 시스템에서 에너지 저장은 전력 수요에 유연하지 않거나 간헐적인 공급의 균형을 이루기 위한 중추적인 역할을 담당할 수 있 을 것이다. 수소는 에너지 담체로서 전기에너지를 화학에너지로, 화학에너지를 전기에너지로 변환할 수 있는 에너지 저장 방 법 중의 하나이다. 수소제조 방법 중에서, 특히, 물의 전기분해를 이용한 방법은 신재생 에너지원과의 접목을 고려할 때 가장 효율적이고 실용적인 방법으로 여겨지고 있다. 물 전기분해 수소제조 기술은 전기를 이용하여 수소를 물로부터 직접 제조하 는 방법으로, 화석연료 이용 제조방법과 비교하여 수소를 제조할 때 지구환경 오염물질인 이산화탄소의 배출이 없다. 수소제 조 방법 중의 하나인 물 전기분해의 원리와 물 전기분해의 종류인 알칼리 수전해(AWE, alkaline water electrolysis), 고분자 전해질막 수전해(PEMWE, polymer electrolyte membrane water electrolysis), 고온 수증기 전기분해(HTSE, high temperature steam electrolysis)에 대하여 분석하고자 하였다. 물 전기분해는 수소제조 방법의 하나로 연구가 진행되고 있으며, 최근에는 PTG (power to gas)와 PTL (power to liquid) 시스템의 요소기술로도 주목을 받고 있다. 본 총설에서는 물 전기분해에 대한 원리와 종류, 특히 알칼리 수전해에 대한 최근 연구동향에 대해 설명하였다.

The potential application of palladium-ruthenium composite membranes to the separation of hydrogen from chlorosilane gases in silicon-based industries was investigated. Ru/Pd/Al2O3/PSS membranes were prepared by electroless plating. Hydrogen permeation tests and temperature programmed desorption analysis revealed that the addition of a Ru over layer on Pd changed the hydrogen adsorption characteristics, resulting in improved stability of the membrane at low temperatures. The Ru/Pd/Al2 O3/PSS composite membrane had a stable hydrogen permeation flux of 1.8 m3m-2h-1 over a period of 1,200 h at 180°C without suffering hydrogen embrittlement. After exposure to impurities such as HCl and SiHCl3 , the hydrogen permeation flux of the Ru/Pd/Al2 O3/PSS composite membrane was stable over a period of 9h with feed pressure of 2.0 bar at 225°C.

화석연료 사용에 의한 환경문제의 해결을 위한 방법의 하나로 수소에너지에 대한 연구가 활발히 진행되고 있다. 물을 분해에 의한 수소 제조는 전기분해, 광화학적, 열화학적, 생물학적 방법 등이 있다. 물의 전기분해 기술은 전기를 이용하여 수소를 물로부터 직접 제조하는 방법으로 지구오염물질인 이산화탄소의 배출이 없는 것이 특징이다. 특히, 물의 전기분해 방법 중에서 알칼리 수전해는 오래전부터 알려진 수소제조 방법으로 전해액으로 ∼30 wt%의 KOH수용액 또는 ∼20 wt%의 NaOH수용액을 사용하며, 셀은 수산화이온 (OH-) 만을 선택적으로 통과시키는 격막, 수소와 산소를 발생시키는 전극으로 구성된다. 최근에는 양.음이온교환막의 발 전과 더불어 전해효율이 60% 이상에 이를 만큼 분리막의 중요성이 부각되고 있다.

We report on the fabrication and characterization of a novel Cu2O/CuO heterojunction structure with CuO nanorods embedded in Cu2O thin film as an efficient photocathode for photoelectrochemical (PEC) solar water splitting. A CuO nanorod array was first prepared on an indium-tin-oxide-coated glass substrate via a seed-mediated hydrothermal synthesis method; then, a Cu2O thin film was electrodeposited onto the CuO nanorod array to form an oxide semiconductor heterostructure. The crystalline phases and morphologies of the heterojunction materials were examined using X-ray diffraction and scanning electron microscopy, as well as Raman scattering. The PEC properties of the fabricated Cu2O/CuO heterojunction photocathode were evaluated by photocurrent conversion efficiency measurements under white light illumination. From the observed PEC current density versus voltage (J-V) behavior, the Cu2O/CuO photocathode was found to exhibit negligible dark current and high photocurrent density, e.g. −1.05 mA/cm2 at −0.6 V vs. Hg/HgCl2 in 1 mM Na2SO4 electrolyte, revealing the effective operation of the oxide heterostructure. The photocurrent conversion efficiency of the Cu2O/CuO photocathode was estimated to be 1.27% at −0.6 V vs. Hg/HgCl2. Moreover, the PEC current density versus time (J-T) profile measured at −0.5 V vs. Hg/HgCl2 on the Cu2O/CuO photocathode indicated a 3-fold increase in the photocurrent density compared to that of a simple Cu2O thin film photocathode. The improved PEC performance was attributed to a certain synergistic effect of the bilayer heterostructure on the light absorption and electron-hole recombination processes.