To investigate the effect of the catalyst and metal–support interaction on the methane decomposition behavior and physical properties of the produced carbon, catalytic decomposition of methane (CDM) was studied using Ni/SiO2 catalysts with different metal–support interactions (synthesized based on the presence or absence of urea). During catalyst synthesis, the addition of urea led to uniform and stable precipitation of the Ni metal precursor on the SiO2 support to produce Ni-phyllosilicates that enhanced the metal–support interaction. The resulting catalyst upon reduction showed the formation of uniform Ni0 particles (< 10 nm) that were smaller than those of a catalyst prepared using a conventional impregnation method (~ 80 nm). The growth mechanisms of methane-decomposition-derived carbon nanotubes was base growth or tip growth according to the metal–support interaction of the catalysts synthesized with and without urea, respectively. As a result, the catalyst with Ni-phyllosilicates resulting from the addition of urea induced highly dispersed and strongly interacting Ni0 active sites and produced carbon nanotubes with a small and uniform diameter via the base-growth mechanism. Considering the results, such a Ni-phyllosilicate-based catalyst are expected to be suitable for industrial base grown carbon nanotube production and application since as-synthesized carbon nanotubes can be easily harvested and the catalyst can be regenerated without being consumed during carbon nanotube extraction process.

Carbon-encapsulated Ni catalysts are synthesized by an electrical explosion of wires (EEW) method and applied for CO2 methanation. We find that the presence of carbon shell on Ni nanoparticles as catalyst can positively affect CO2 methanation reaction. Ni@5C that is produced under 5% CH4 partial pressure in Ar gas has highest conversions of 68 % at 350 oC and 70% at 400 oC, which are 73 and 75% of the thermodynamic equilibrium conversion, respectively. The catalyst of Ni@10C with thicker carbon layer shows much reduced activity. The EEW-produced Ni catalysts with low specific surface area outperform Ni catalysts with high surface area synthesized by solution-based precipitation methods. Our finding in this study shows the possibility of utilizing carbon-encapsulated metal catalysts for heterogeneous catalysis reaction including CO2 methanation. Furthermore, EEW, which is a highly promising method for massive production of metal nanoparticles, can be applied for various catalysis system, requiring scaled-up synthesis of catalysts.

Ni–Cr–Al metal-foam-supported catalysts for steam methane reforming (SMR) are manufactured by applying a catalytic Ni/Al2O3 sol–gel coating to powder alloyed metallic foam. The structure, microstructure, mechanical stability, and hydrogen yield efficiency of the obtained catalysts are evaluated. The structural and microstructural characteristics show that the catalyst is well coated on the open-pore Ni–Cr–Al foam without cracks or spallation. The measured compressive yield strengths are 2–3 MPa at room temperature and 1.5–2.2 MPa at 750oC regardless of sample size. The specimens exhibit a weight loss of up to 9–10% at elevated temperature owing to the spallation of the Ni/Al2O3 catalyst. However, the metal-foam-supported catalyst appears to have higher mechanical stability than ceramic pellet catalysts. In SMR simulations tests, a methane conversion ratio of up to 96% is obtained with a high hydrogen yield efficiency of 82%.

The autothermal reforming reaction of methane was investigated to produce hyd rogen with Ni/CeO2-ZrO2, Ni/Al2O3-MgO and Ni-Ru/Al2O3-MgO catalysts. Honeycomb metalli c monolith was applied in order to obtain high catalytic activity and stability in autothermal r eforming. The catalysts were characterized by XRD, BET and SEM. The influence of various catalysts on hydrogen production was studied for the feed ratio(O2/CH4, H2O/CH4). The O2/CH4 and H2O/CH4 ratio governed the methane conversion and temperature profile of reactor. Th e reactor temperature increased as the reaction shifted from endothermic to exothermic reactio n with increasing O2/CH4 ratio. Among the catalysts used in the experiment, the Ni-Ru/Al2O3-MgO catalyst showed the highest activity. The 60% of CH4 conversion was obtained, and th e reactor temperature was maintained 600℃ at the condition of GHSV=10000h-1 and feed ratio S/C/O=0.5/1/0.5.

The effects of La addition to Ni/CeO2 methane partial oxidation catalysts were investigated. Catalysts were prepared by the impregnation and urea methods. In the preparation of catalysts, La content was changed from 1 wt% to 3wt%. Catalysts that contain 2wt% La showed the highest methane conversion of about 80% and CO selectivity of 84% and H2 selectivity of 70%. This result may be stemmed from that, when La content is 2wt%, a fluorite oxide-type structure is well formed and carbon deposition is also decreased. Among the catalysts, 2.5wt% Ni/Ce(La)Ox showed the highest catalytic activity. From the experiment of changing reaction temperature with 2.5wt% Ni/Ce(La)Ox catalyst, it was found that the optimum reaction temperature is 750℃ and at this temperature methane conversion was about 90%, CO and H2 selectivities were 94 and 80%, respectively.

The electrocatalytic characteristics of oxygen reduction reaction of the PtxM(1-x) (M = Co, Cu, Ni) supported on multi-walled carbon nanotubes (MWNTs) have been evaluated in a Polymer Electrolyte Membrane Fuel Cell (PEMFC). The PtxM(1-x)/MWNTs catalysts with a Pt : M atomic ratio of about 3 : 1 were synthesized and applied to the cathode of PEMFC. The crystalline structure and morphology images of the PtxM(1-x) particles were characterized by X-ray diffraction and transmission electron microscopy, respectively. The results showed that the crystalline structure of the Pt alloy particles in Pt/MWNTs and PtxM(1-x)/MWNTs catalysts are seen as FCC, and synthesized PtxM(1-x) crystals have lattice parameters smaller than the pure Pt crystal. According to the electrochemical surface area (ESA) calculated with cyclic voltammetry analysis, Pt0.77Co0.23/MWNTs catalyst has higher ESA than the other catalysts. The evaluation of a unit cell test using Pt/MWNTs or PtxM(1-x)/MWNTs as the cathode catalysts demonstrated higher cell performance than did a commercial Pt/C catalyst. Among the MWNTs-supported Pt and PtxM(1-x) (M = Co, Cu, Ni) catalysts, the Pt0.77Co0.23/MWNTs shows the highest performance with the cathode catalyst of PEMFC because they had the largest ESA.

The effect of La promoter on the carbon deposition and catalytic activity in the synthesis gas production with supported Ni catalysts was investigated. Active component was Ni and support was CeO2 and the promoter used was La. The reaction was carried out in a fixed bed reactor at 1 atm and 650~800℃. The catalysts were prepared by two methods, the impregnation method and urea method. The catalysts prepared by the urea method showed 10 times higher surface area than those of prepared by the impregnation method. By the introduction of La promoter in the catalyst system, carbon deposition was remarkably reduced from 16% to 2%. It appears that the promoter facilitates the formation of a stable fluoride-type phase, which reduces the carbon deposition. The best catalytic activity and CO and H2 selectivities were obtained with 2.5wt% Ni/Ce(La)Ox catalyst at 750℃, giving 90% methane conversion, 93 and.80% of CO and H2 selectivities, respectively.

Synthesis gas is produced commercially by a steam reforming process. However, the process is highly endothermic and energy intensive. Thus, this study was conducted to produce synthesis gas by the partial oxidation of methane to cut down the energy cost. Supported Ni catalysts were prepared by the impregnation method. To examine the activity of the catalysts, a differential fixed bed reactor was used, and the reaction was carried out at 750~850℃ and 1 atm. The fresh and used catalysts were characterized by XRD, XPS, TGA and AAS. The highest catalytic activity was obtained with the 13wt% Ni/MgO catalyst, with which methane conversion was 81%, and H2 and CO selectivities were 94% and 93%, respectively. 13wt% Ni/MgO catalyst showed the best MgNiO2 solid solution state, which can explain the highest catalytic activity of the 13wt% Ni/MgO catalyst.

Synthesis gas is commercially produced by a steam reforming process. However, the process is highly endothermic and energy-consuming. Thus, this study was conducted to produce synthesis gas by the partial oxidation of methane to decrease the energy cost. Supported Ni catalysts were prepared by the impregnation method. To examine the activity of the catalysts, a differential fixed bed reactor was used, and the reaction was carried out at 750~850℃ and 1 atm. The fresh and used catalysts were characterized by XRD, XPS, TGA and AAS. The highest catalytic activity was obtained with the 13wt% Ni/MgO catalyst, with which methane conversion was 81%, and H2 and CO selectivities were 94% and 93%, respectively. 13wt% Ni/MgO catalyst showed the best MgNiO2 solid solution state, which can explain the highest catalytic activity of the 13wt% Ni/MgO catalyst.

고분자전해질형 연료전지에서 촉매의 활성을 증가시키기 위하여 기존에 사용되고 있는 백금과 전이금속인 chromium, nickel과의 합금을 제조하였다. XRD를 이용하여 합금의 구조가 33˚에서 superlattice line을 가지고 있는 것으로 보아 face centered cubic 구조를 가진 ordered alloy로 이루어졌다는 것을 알 수 있었다. 열처리 온도가 증가할수록 합금의 입자 크기는 증가하였으며, 결정 격자 상수는 감소하였다. 전지성능테스트, cyclic voltammogram 등을 통하여 mass activity, specific activity, Tafel slope, 개회로 전압을 측정한 결과, 합금촉매의 활성이 순수한 백금촉매보다 크게 향상되었음을 알 수 있었다.

상업적으로 HTS (High Temperature Shift reaction) 반응에서 사용되는 Fe2O3/Cr2O3 촉매는 사용 후 6가 크롬 (Cr6+)의 침출에 따른 환경적/인체적 문제를 일으킬 수 있는 잠재성을 가지고 있어 친환경 크롬-프리 촉매개발을 위한 연구가 활발히 진행되고 있다. 본 연구에서는 크롬을 사용하지 않고 우수한 성능을 나타낼 수 있는 Fe/Al, Fe/Al/Cu, 그리고, Fe/Al/Ni 촉매를 제조하고 성능을 비교 평가하였다. 단계함침법으로 금속산화물(Cu와 Ni)과 알루미늄이 함유된 Fe계 촉매를 제조하고 촉매반응장치를 이용하여 각 촉매의 활성을 분석하였다. 그 결과 Fe/Al/Cu 촉매는 가혹한 조건(COconc. = 38.2%; 천연가스 대비 약 5.7 배 높은 CO 농도)에서도 탁월한 성능(XCO = 84.3% at 400 ℃)을 나타내었다. 이 결과는 Fe/Al/Cu 촉매의 강한 환원력과 활성종인 Fe3O4의 높은 열적 안정성에 기인한 것으로 확인되었다. 또한 강한 소결 저항성을 가진 Fe/Al/Cu 촉매는 400°C에서 100시간 동안 뚜렷한 비활성화를 보이지 않아 높은 안정성을 지닌 것으로 확인되었다.