This work reported the electrochemical and photoelectrochemical (PEC) properties of a new photoelectrode based on hematite Co-Fe2O3@NiO, a photoactive semiconductor, was prepared using a process involving a combination of the co-precipitation and microwave-assisted synthesis of Fe2O3, Co-Fe2O3 and Co-Fe2O3@NiO, respectively. The obtained products were characterized by X-Ray powder Diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive X-ray analysis (EDX), Ultraviolet–Visible (UV–vis) analysis, Fourier Transform Infrared spectroscopy (FT-IR). X-ray diffraction (XRD) pattern of the sample determined the crystal structure of α-Fe2O3 nanoparticles. The SEM image shows spherical nanoparticles. FTIR spectrospy spectrum confirmed the phase purity and chemical bond for the sample. Optical studies show a variation of band gap from 2.118 to 2.07 eV. The electrochemical and photoelectrochemical (PEC) performance of the films were examined by cyclic voltammetry, linear sweep voltammetry and chronoamperometry. The electrochemical oxidation of water achieved by Cobalt-doped Fe2O3@ GCE modified electrode exhibited the current density of 21 mA/g at 0.5 V vs. SCE for 5 at% of Co and reveals enhanced specific capacitance of 352.11 F/g. The catalytic performance of urea oxidation was measured by cyclic voltammetry on Co-Fe2O3@NiO nanoparticles modified glassy carbon electrode (GCE) in alkaline medium. The electrode Co-Fe2O3@NiO without annealing showed a peak current density of 1.59 mA/cm2 at 0.1 M urea in 1.0 M NaOH, which was 3.6 fold higher than that of Co-Fe2O3@NiO with annealing. In another part, this work reported the photoelectrochemical (PEC) properties of photoanode prepared by spin coating. The highest photocurrent 0.042 mA/cm2 at 0.5 V Vs SCE was obtained for 5% Co-Fe2O3@NiO while the photocatalytic oxidation of urea.

Based on the M06-2X density functional, the catalytic oxidation of CO by O2 over Mo-embedded graphene was investigated in detail. The model with molybdenum atom embedded in double vacancy (DV) in a graphene sheet was considered. It is found that the complete CO oxidation reactions over Mo-DV-graphene include a two-step process, in which the first step prefers to Langmuir–Hinshelwood mechanism and followed the progress of CO oxidation with a remaining atomic Otop. Compared with the structure of Mo atom decorated at the single carbon vacancy on graphene (Mo-SV-graphene), the catalytic activity of Mo-DV-graphene is weaker. The present results imply that the catalytic activity of Mo-embedded graphene for CO oxidation can be improved by increasing the ratio of single vacancy (SV).

고분자 전해질 연료전지의 연료에 포함된 일산화탄소의 선택적 산화를 위하여, 귀금속 촉매를 대체하기 위한 CuO-CeO2 복합 산화물 촉매를 졸-겔법과 공침법으로 제조하였다. 졸-겔법으로 촉매 제조 시 Cu/Ce의 비와 가수분해 비를 변화시켰다. 제조한 촉매의 활성은 귀금속 촉매(Pt/γ-Al2O3)와 비교하였다. Cu/Ce의 비를 변화시키면서 제조한 촉매 중 Cu/Ce의 비가 4:16인 촉매가 가장 높은 CO 전환율(90%)과 선택도(60%)를 나타내었다. 촉매의 제조에서 가수분해 비가 증가할수록 촉매 표면적이 증가하였고, 아울러 촉매 활성 또한 증가하였다. 공침법으로 제조한 촉매와 1wt% Pt/γ-Al2O3 촉매의 가장 높은 CO 전환율은 각각 82% 및 81%인 반면, 졸-겔법으로 제조한 촉매의 경우는 90%가 얻어졌다. 이는 졸-겔법으로 제조한 촉매가 공침법으로 제조한 촉매나 귀금속 촉매보다 더 높은 촉매활성을 보임을 의미한다. CO-TPD 실험을 통하여, 낮은 온도(140℃)에서 CO를 탈착하는 촉매가 본 반응에서 더 높은 촉매활성을 보임을 알 수 있었다.

Cu-Mn과 Cu-Zn 촉매를 침전제로 다르게 하거나, 금속의 몰비율, 소성온도를 다르게 하여 공침법으로 제조하였고 CO산화반응을 수행하여 혼합산화물 촉매에서 Cu, Mn과 Zn의 영향 및 소성온 도가 미치는 영향을 조사하였다. 촉매의 물리·화학적 특성을 알아보기 위하여 XRD, N2 흡착 및 SEM 의 분석을 수행하였다. Na2CO3로 침전시켜 270℃로 소성하여 제조한 2Cu-1Mn 산화물 촉매가 저온에 서 CO 산화반응 활성이 가장 좋았으며 2Cu-1Mn 산화물 촉매는 43 m2/g으로 가장 높은 비표면적과 촉매 활성을 나타내었다. XRD로 촉매의 결정구조를 분석하였을 때 Cu0.5Mn2.5O4의 결정구조를 갖는 촉 매는 낮은 활성을 보였다. 270℃에서 소성한 촉매가 좋은 활성을 나타냈으며 Pt 촉매와 비교하여도 저 온에서 CO산화반응이 더욱 우수함을 알 수 있었다.

This study shows that catalytic activity of bimetallic RhPt nanoparticle arrays under CO oxidation can be tuned by varying the size and composition of nanoparticles. The tuning of size of RhPt nanoparticles was achieved by changing concentration of rhodium and platinum precursors in one-step polyol synthesis. Two-dimensional RhPt bimetallic nanoparticle arrays in different size and composition were prepared through Langmuir-Blodgett thin film technique. CO oxidation was carried out on these two-dimensional nanoparticle arrays, revealing higher activity on the smaller nanoparticles compared to the bigger nanoparticles. X-ray photoelectron spectroscopy (XPS) results indicate the preferential surface segregation of Rh compared to Pt on the smaller nanoparticles, which is consistent with the thermodynamic analysis. Because the catalytic activity is associated with differences in the rates of dissociative adsorption between Pt and Rh, this paper suppose that the surface segregation of Rh on the smaller bimetallic nanoparticles is responsible for the higher catalytic activity in CO oxidation. This result suggests a control mechanism of catalytic activity via synthetic approaches of colloid nanoparticles, with possible application in rational design of nanocatalysts.

The oxidation behavior of 91 WC-9Co hardmetal in weight percentage has been studied in the present work as a part of the development of recycling process. The morphological and compositional changes of the WC-Co hardmetal with oxidation time at 90 were analyzed by using surface observation and X-ray diffraction. respective]y. As the oxidation time increased, the WC-Co hardmetal was continuously expanded to form porous oxide mixtures of and . The morphology of porous oxide mixture was basically dependent on initial shape of the WC-Co hardmetal. From thermo-gravimetric (TG) analysis, it was found that the oxidation rate was increased with increasing oxidation temperature and oxygen content in the flowing atmospheric gas. The fraction of oxidation versus time curves showed S-curve relationship at a given of oxidation temperature. These oxidation behaviors of the WC-Co hardmetal were discussed in terms of previously proposed kinetic models.

이방성과 등방성을 갖는 두 종류의 피치계 탄소섬유를 TGA장치를 이용하여 CO2gas와 공기중에서 등온산화반응을 실시하였다. CO2 gas보다 공기중에서의 산화가 훨씬 빠르게 일어났으며, 600˚C공기중에서 등방성 T-10IS섬유는 이방성 HM-60섬유보다 23.9배나 빠른 산화속도를 보였다. 실험적으로 구한 활성화에너지를 저온에서 36-56Kcal/mole의 값을 가지며, 고온에서는 6-13Kcal/mole의 값을 나타내었다. 반응기구(zone 1,2,3)의 천이도는 T-10IS섬유보다 HM-60 섬유가 높았으며, 공기중에서보다 CO2 gas분위기에서 더 높게 나타났다. SEM으로 관찰된 표면상변화로부터 탄소섬유의 산화반응은 섬유의 결함을 따라 진행된다는 것을 알 수 있었다.

The effect of vacuum annealing on the oxidation behavior of milled WC-15%Co powder mixture has been studied. A cobalt component in the milled powder mixture was oxidized preferentially above 175 in air. The specimens showed a steady increase in weight at 175 but did constant weight followed by rapid increase in specimen weight at the beginning above 20. Oxidation of the milled powder mixture was significantly suppressed by vacuum annealing at 30 for 10 h. Suppression of oxidation by vacuum annealing and different oxidation behaviors of the milled powder mixture between 175 and 20, were attributed to removal of strain energy stored in the cobalt powder during vacuum annealing or oxidation treatment above 20. The role of stored strain energy on oxidation of milled WC-15%Co powder mixture was proved by X-ray diffraction method and differential thermal analysis.

A novel pretreatment technique was applied to the conventional Pt/alumina catalyst to prepare for the highly efficient catalyst for the preferential oxidation of carbon monoxide in hydrogen-rich condition. Their performance was investigated by selective CO oxidation reaction. CO conversion with the oxygen-treated Pt/Alumina catalyst increased remarkably especially at the low temperature below 100℃. This result is promising for the normal operation of the proton exchange membrane fuel cell (PEMFC) without CO poisoning of the anode catalyst. XRD analysis results showed that metallic Pt peaks were not observed for the oxygen-treated catalyst. This implies that well dispersed small Pt particles exist on the catalyst. This result was confirmed by high resolution transmission electron microscopy (HRTEM) analysis. Consequently, it can be concluded that highly dispersed Pt nanoparticles could be prepared by the novel pretreatment technique and thus, CO conversion could be increased considerably especially at the low temperatures below 100℃.

Hydrogen gas is used as a fuel for the proton exchange membrane fuel cell (PEMFC). Trace amount of carbon monoxide present in the reformate H₂ gas can poison the anode of the PEMFC. Therefore, preferential oxidation (PROX) of CO is essential for reducing the concentration of CO from a hydrogen-rich reformate gas. In this study, conventional Pt/Al₂O₃catalyst was prepared for the preferential oxidation of CO. The effects of catalyst preparation method, additive, and hydrogen on the performances of PROX reaction of CO were investigated. Water treatment and addition of Ce enhanced catalytic activity of the Pt/Al₂O₃ catalyst at low temperature below 100℃.

The formation of ConTiOn+₂ compounds, i.e., CoTiO₃ and Co2TiO₄, in a 5 wt% CoOx/TiO2 catalyst after calcination at different temperatures has been characterized via scanning electron microscopy (SEM), Raman and X-ray photoelectron spectroscopy (XPS) measurements to verify our earlier model associated with Co3O4 nanoparticles present in the catalyst, and laboratory-synthesized ConTiOn+₂ chemicals have been employed to directly measure their activity profiles for CO oxidation at 100˚C. SEM measurements with the synthetic CoTiO₃ and Co2TiO₄ gave the respective tetragonal and rhombohedral morphology structures, in good agreement with the earlier XRD results. Weak Raman peaks at 239, 267 and 336 cm-1 appeared on 5 wt% CoOx/TiO₂ after calcination at 570oC but not on the catalyst calcined at 450˚C, and these peaks were observed for the ConTiOn+₂ compounds, particularly CoTiO3. All samples of the two cobalt titanate possessed O 1s XPS spectra comprised of strong peaks at 530.0±0.1 eV with a shoulder at a 532.2-eV binding energy. The O 1s structure at binding energies near 530.0 eV was shown for a sample of 5 wt% CoOx/TiO₂, irrespective to calcination temperature. The noticeable difference between the catalyst calcined at 450 and 570˚C is the 532.2 eV shoulder which was indicative of the formation of the ConTiOn+₂ compounds in the catalyst. No long-life activity maintenance of the synthetic ConTiOn+₂ compounds for CO oxidation at 100˚C was a good vehicle to strongly support the reason why the supported CoOx catalyst after calcination at 570˚C had been practically inactive for the oxidation reaction in our previous study; consequently, the earlier proposed model for the Co₃O₄ nanoparticles existing with the catalyst following calcination at different temperatures is very consistent with the characterization results and activity measurements with the cobalt titanates.