http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
AHMED SHERAZ,카즈미 와자하트 와히드,Hussain Amjad,Khan Muhammad Zubair,Bibi Saira,Saleem Mohsin,송락현,Sajid Zaman,Ullah Abid,Muhammad Kashif Khan 한국세라믹학회 2023 한국세라믹학회지 Vol.60 No.2
Herein, we report a facilely synthesized Sm0.5Sr0.5CoO3 (SSC) nano-catalyst as a cathode material for the solid oxide fuel cell (SOFC). The SSC nano-catalyst was synthesized by a sol–gel process using citric acid and metal nitrates and calcination was performed at a relatively low temperature of 1250 ℃. The crystallinity and morphology of the catalyst were observed by the X-ray diffraction and scanning electron microscope. The average particle size of the SSC powder was 100 nm after calcination at 1250 °C. The resulting SSC material was employed as a cathode for the SOFC. The SOFC cell with highly active SSC showed a peak power density of 900 mWcm−2 at 700 °C. The single cell with an SSC cathode showed excellent stability under the accelerated operating conditions of 0.5A/cm2 and 650 °C for 1250 min. The cell performance was enhanced during the initial hours of the long-term operation which is attributed to the cathode activation process and improved cathode/buffer layer interface contact. This work features a cost-effective, scalable, and reproducible method for the production of highly robust SSC cathode material for the SOFC under relatively low calcination temperatures.
Sheraz Ahmed,심중표,박경세 대한화학회 2024 대한화학회지 Vol.68 No.2
The commercialization of rechargeable metal-air batteries is extremely desirable but designing stable oxygen reduction reaction (ORR) catalysts with non-noble metal still has faced challenges to replace platinum-based catalysts. The nonnoble metal catalysts for ORR were prepared to improve the catalytic performance and stability by the thermal decomposition of ZIF-8 with optimum cobalt loading. The porous carbon was obtained by the calcination of ZIF-8 and different loading amounts of Co nanoparticles were anchored onto porous carbon forming a Co/PC catalyst. Co/PC composite shows a significant increase in the ORR value of current and stability (500 h) due to the good electronic conductive PCN support and optimum cobalt metal loading. The significantly improved catalytic performance is ascribed to the chemical structure, synergistic effects, porous carbon networks, and rich active sites. This method develops a new pathway for a highly active and advantageous catalyst for electrochemical devices.
Ahmed Sheraz,Rim Hyung‐Ryul,Sun Ho‐Jung,Lee Hong‐Ki,Shim Joongpyo,Park Gyungse 대한화학회 2022 Bulletin of the Korean Chemical Society Vol.43 No.5
The application of heteroatom doped cobalt (Ni@Co/C) prepared from a porous metal–organic framework as the cathode material for the rechargeable zinc–air batteries has been demonstrated. The Ni@Co/C-modified electrode showed an excellent catalytic activity toward oxidation–reduction reaction and oxygen evolution reactions. The Co/C catalysts, which were Co particle impregnated on graphitic carbon powders, were synthesized after the calcination of Co3 (SDA)3(DMF)2 precursor, and then Ni deposition (Ni@Co/C) was followed on it by chemical reduction. Linear sweep voltammetry measurement indicates that Ni@Co/C-H800, which had Ni particles on Co/C derived from MOF at 800 C under N2, exhibited excellent performance. The stable charging/discharging profiles at 20 mA cm2 of current were obtained for the 350 h in alkaline medium, suggesting Ni@Co/C-H800 as a potential candidate for oxidation– reduction and evolution reactions.
국윤승,Sheraz Ahmed,선호정,심중표,박경세 대한화학회 2020 Bulletin of the Korean Chemical Society Vol.41 No.3
A metal?organic framework (MOF) was synthesized using 4,4?-stilbenedicarboxylic acid (H2SDA) in dimethylformamide (DMF). Carbon-coated Co (C@Co) catalysts were prepared by the direct calcination of Co3(SDA)3(DMF)2 MOF crystals at various temperatures. The highest surface area of the C@Co catalyst is obtained at 600?°C which can further be increased by the ball mill operation. The X-ray photon spectroscopy and X-ray diffraction analysis proved the formation of metallic Co in the carbon matrix at temperatures over 500?°C, while Co3O4 formation was observed at 500?°C. Furthermore, the graphitic properties of the Co particles were analyzed by Raman spectroscopy. The durability of the carbon-coated Co catalysts derived from MOFs (C@Co catalysts) was analyzed by the cycle test (charge/discharge at 20?mA/cm2 per 2 h) and was retained over 350?h. These catalysts showed remarkable stability for both ORR (oxygen reduction reaction) and OER (oxygen evolution reaction), comparable to that of Co3O4 and Co metal powder in alkaline solution.
Aiman Fatima,Syed Sheraz Daood,Shafia Inaam,Zaeem Bin Babar,Ashfaq Ahmed,Muhammad Zafar,Tahir Maqsood Qaisrani,Abdul Razzaq,Muhammad Usman Rashid,Sunhyung Kim,Young-Kwon Park 대한환경공학회 2023 Environmental Engineering Research Vol.28 No.3
Fluorite (fluorspar), an important industrial mineral ore, is one of the major raw materials for the production of hydrofluoric acid. Naturally occurring fluorite ore contains gangue minerals, primarily silica (SiO2) and calcite (CaCO3). The beneficiation of fluorspar is needed to mitigate the severity of operational issues. Several studies on fluorspar beneficiation using the froth floatation technique have been executed, but the process is restricted by the use of minerals acids to remove calcite. In this study, a novel scheme for fluorspar beneficiation was investigated for the floatation of fluorite and depression of calcite and other gangue minerals simultaneously without the use of mineral acids. Moreover, mixtures of saturated and unsaturated fatty acids (oleic acid and palmitic acid) were used instead of mineral acids. Various parameters were investigated, such as the weight percent of the feed-slurry, feed pH, the effect of reagents on the process selectivity, and the effect of feed boiling and dilution on the up-gradation of fluorspar. The adopted methodology with tested reagents resulted a 67 wt. % reduction of CO32− and 75 wt. % reduction of SiO2 in gangue material at a pH 10 for the feed slurry. Fluorspar purity increased from 65–75 wt. % to 95 wt. % after the boiling and dilution steps, respectively.
Hao Nguyen Thi My,Ahmed Sheraz,An Jung‐Chul,Sun Ho‐Jung,Park Gyungse,Shim Joongpyo 대한화학회 2021 Bulletin of the Korean Chemical Society Vol.42 No.9
Co and carbon nanotube (CNT) were prepared as anode materials to be used in lithium rechargeable batteries from the zeolitic-imidazolate framework-67 (ZIF-67) using the solvothermal method. By annealing ZIF-67 at different temperatures between 400 and 700 C, the carbon framework was changed to CNTs, and Co or Co3O4 nanoparticles were embedded in the CNTs (Co or Co3O4/CNT). The Co/CNT was converted to Co-Co3O4/CNT by further treatment at 160 C in air. The Co3O4/CNT showed high initial capacities (1582 mAh/g) but poor capacity retention during cycling. However, the air treatment of the Co/CNT at 160 C enhanced its discharge capacity (935 mAh/g) and capacity retention during cycling.