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排序方式: 共有44条查询结果,搜索用时 15 毫秒
1.
Bakowski M. Cockrum R. H. Zamani N. Maserjian J. Viswanathant C. R. 《IEEE transactions on nuclear science》1978,25(6):1233-1238
Avalanche-injection of holes and electrons into nonirradiated and irradiated MOS capacitors, respectively, were used to study hole traps in the SiO2. The trapping parameters for holes, and for electrons in the presence of trapped holes, were obtained in the range 10-14 - 10-13 cm2 for oxide thicknesses in the range 200 - 1000?. A dominant bulk specie is determined to tail off from the Si/SiO2 interface with a characteristic distance of 150-200? for dry oxide and approximately 400? for wet oxide. The electron-injection is shown to be an effective probe of the trapped-hole distribution in the SiO2 after irradiation. The effect of electron compensation of trapped holes during irradiation had been included in the trapping kinetics. C-V shifts and interface state build-up near mid- band after irradiation were found, from irradiation experiments, to follow the same linear dependence on the integrated electron and hole flux crossing the Si/SiO2 interface. 相似文献
2.
Laser-beam-excited photocurrent measurements of the space-charge layer width close to the surface of a negatively bevelled diffused p-n junction revealed the existence of a well defined region of carrier multiplication at high applied voltages. The region is located within the space-charge layer on the highly doped side of the junction and close to the surface. The laser-light wavelength was 6328 ? and the beam diameter was about 5 ?m. The experimental results are consistent with the theoretically predicted existence of a field maximum in this region of negatively bevelled p-n junctions. 相似文献
3.
A novel colloid-imprinting method is employed for the preparation of carbonaceous stationary phases for reversed-phase liquid chromatography (RPLC). This colloid-imprinting method combined with oxidative stabilization treatment affords carbons with a porous shell/nonporous core structure. The particle morphology, pore size, pore shape, and Brunauer-Emmett-Teller surface area of these carbons can be finely tuned by selecting proper experimental conditions. Although their surface area and pore volume decrease noticeably after graphitization, their primary pore structure is maintained. In addition, the graphitization process eliminates the high-energy sites and substantially reduces structural heterogeneity, making colloid-imprinted carbons attractive stationary phases for reversed-phase liquid chromatography. The colloid-imprinted graphitic carbons with surface mesoporosity appeared to be attractive for chromatographic separations of alkylbenzenes under reversed-phase conditions. 相似文献
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5.
Peng Zhou Jiaguo Yu Mietek Jaroniec 《Advanced materials (Deerfield Beach, Fla.)》2014,26(29):4920-4935
The current rapid industrial development causes the serious energy and environmental crises. Photocatalyts provide a potential strategy to solve these problems because these materials not only can directly convert solar energy into usable or storable energy resources but also can decompose organic pollutants under solar‐light irradiation. However, the aforementioned applications require photocatalysts with a wide absorption range, long‐term stability, high charge‐separation efficiency and strong redox ability. Unfortunately, it is often difficult for a single‐component photocatalyst to simultaneously fulfill all these requirements. The artificial heterogeneous Z‐scheme photocatalytic systems, mimicking the natural photosynthesis process, overcome the drawbacks of single‐component photocatalysts and satisfy those aforementioned requirements. Such multi‐task systems have been extensively investigated in the past decade. Especially, the all‐solid‐state Z‐scheme photocatalytic systems without redox pair have been widely used in the water splitting, solar cells, degradation of pollutants and CO2 conversion, which have a huge potential to solve the current energy and environmental crises facing the modern industrial development. Thus, this review gives a concise overview of the all‐solid‐state Z‐scheme photocatalytic systems, including their composition, construction, optimization and applications. 相似文献
6.
Quanlong Xu Liuyang Zhang Jiaguo Yu Swelm Wageh Ahmed A. Al-Ghamdi Mietek Jaroniec 《Materials Today》2018,21(10):1042-1063
The properly designed semiconductor photocatalysts are promising materials for solving the current serious energy and environmental issues because of their ability of using sunlight to stimulate various photocatalytic reactions. Especially, the constructed direct Z-scheme photocatalysts, mimicking the natural photosynthesis system, possess many merits, including increased light harvesting, spatially separated reductive and oxidative active sites, and well-preserved strong redox ability, which benefit the photocatalytic performance. This review concisely compiles the recent progress in the fabrication, modification, and major applications of the direct Z-scheme photocatalysts; the latter include water splitting, carbon dioxide reduction, degradation of pollutants, and biohazard disinfection. It finishes with a brief presentation of future challenges and prospects in the development of direct Z-scheme photocatalytic systems. 相似文献
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8.
Significant Enhancement of Water Splitting Activity of N‐Carbon Electrocatalyst by Trace Level Co Doping
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Bita Bayatsarmadi Yao Zheng Youhong Tang Mietek Jaroniec Shi‐Zhang Qiao 《Small (Weinheim an der Bergstrasse, Germany)》2016,12(27):3703-3711
Replacement of precious metal electrocatalysts with highly active and cost efficient alternatives for complete water splitting at low voltage has attracted a growing attention in recent years. Here, this study reports a carbon‐based composite co‐doped with nitrogen and trace amount of metallic cobalt (1 at%) as a bifunctional electrocatalyst for water splitting at low overpotential and high current density. An excellent electrochemical activity of the newly developed electrocatalyst originates from its graphitic nanostructure and highly active Co‐Nx sites. In the case of carefully optimized sample of this electrocatalyst, 10 mA cm?2 current density can be achieved for two half reactions in alkaline solutions—hydrogen evolution reaction and oxygen evolution reaction—at low overpotentials of 220 and 350 mV, respectively, which are smaller than those previously reported for nonprecious metal and metal‐free counterparts. Based on the spectroscopic and electrochemical investigations, the newly identified Co‐Nx sites in the carbon framework are responsible for high electrocatalytic activity of the Co,N‐doped carbon. This study indicates that a trace level of the introduced Co into N‐doped carbon can significantly enhance its electrocatalytic activity toward water splitting. 相似文献
9.
Cocatalysts in Semiconductor‐based Photocatalytic CO2 Reduction: Achievements,Challenges, and Opportunities
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Ever‐increasing fossil‐fuel combustion along with massive CO2 emissions has aroused a global energy crisis and climate change. Photocatalytic CO2 reduction represents a promising strategy for clean, cost‐effective, and environmentally friendly conversion of CO2 into hydrocarbon fuels by utilizing solar energy. This strategy combines the reductive half‐reaction of CO2 conversion with an oxidative half reaction, e.g., H2O oxidation, to create a carbon‐neutral cycle, presenting a viable solution to global energy and environmental problems. There are three pivotal processes in photocatalytic CO2 conversion: (i) solar‐light absorption, (ii) charge separation/migration, and (iii) catalytic CO2 reduction and H2O oxidation. While significant progress is made in optimizing the first two processes, much less research is conducted toward enhancing the efficiency of the third step, which requires the presence of cocatalysts. In general, cocatalysts play four important roles: (i) boosting charge separation/transfer, (ii) improving the activity and selectivity of CO2 reduction, (iii) enhancing the stability of photocatalysts, and (iv) suppressing side or back reactions. Herein, for the first time, all the developed CO2‐reduction cocatalysts for semiconductor‐based photocatalytic CO2 conversion are summarized, and their functions and mechanisms are discussed. Finally, perspectives in this emerging area are provided. 相似文献
10.
Tao Ling Mietek Jaroniec Shi-Zhang Qiao 《Advanced materials (Deerfield Beach, Fla.)》2020,32(46):2001866
In the past few decades, tremendous advances have been made in electrocatalysis due to the rational design of electrocatalysts at the nanoscale level. Further development requires engineering electrocatalysts at the atomic level, which is a grand challenge. Here, the recent advances in cation exchange strategy, which is a powerful tool for fine-tuning atomic structure of electrocatalysts via surface faceting, heteroatom doping, defects formation, and strain modulation, are the main focus. Proper atomic structure engineering effectively adjusts the electronic structure, and thus enhances the electronic conductivity and facilitates the adsorption/desorption of reaction intermediates. By virtue, the cation exchange strategy greatly boosts the intrinsic and apparent activities of electrocatalysts and shows a great potential toward design of new energy conversion devices, such as water splitting devices and metal–air batteries. It is believed that cation exchange offers new insights and opportunities for the rational design of a new generation of electrocatalysts. 相似文献