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本文研究了甲基丙烯酸及其甲酯与分子氧O2的初始氧化反应?随着通O2后密封放置时间的增加,MMA中所生成的氢过氧化物浓度逐渐增加。而MAA中却无变化。 相似文献
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本文用EMF及化学分析方法研究了富钛(25(wt)%TiO2)氧化物熔渣体系中低价钛氧化的动力学规律,探讨了添加铁氧化物对改善熔渣氧传输动力学条件的机制,及渣中低价钛的氧化与相关耦合反应的关系。 相似文献
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以La0.8Sr0.2Fe0.9CO0.1O3钙钛矿氧化物作氧载体,采用连续流动反应和连续顺序Redox反应考察了氧物种氧化甲烷的反应性能.结果表明,连续流动反应中La0.8Sr0.2Fe0.9CO0.1O3氧化物的氧物种能选择氧化甲烷生成合成气.在适宜的再氧化条件下,通过连续顺序Redox反应实现了La0.8Sr0.2Fe0.9CO0.1O3氧化物的氧物种氧化甲烷连续生成合成气,消耗的氧物种可通过与气相氧反应而得到补充.但随着Redox反应的进行,氧化物的持续供氧性能下降,钙钛矿结构被破坏. 相似文献
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CaO的晶格氧对甲烷能发生非选择性氧化反应,经反应消耗的晶格氧可以由气相氧中补充,也可以通过体相晶格氧向表面的迁移来补充。Na ̄+添加剂能抑制CaO晶格氧的反应活性,当Na ̄+含量达到5%时,CaO晶格氧对甲烷的完全氧化活性被完全抑制。Ca_xSr_(1-x)TiO_3复合氧化物催化剂的晶格氧对甲烷没有活性。只有当气相氧存在时,在5%Na ̄+/CaO和Ca_xSr_(1-x)TiO_3复合氧化物上才能通过气相氧向表面氧物种的转化而引发甲烷氧化偶联反应。 相似文献
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《结构化学》2020,39(12):2115-2122
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Dr. Ting Ouyang Dr. Xiao-Tong Wang Xiu-Qiong Mai An-Na Chen Zi-Yuan Tang Prof. Zhao-Qing Liu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(29):12046-12055
Transition-metal oxides as electrocatalysts for the oxygen evolution reaction (OER) provide a promising route to face the energy and environmental crisis issues. Although palmeirite oxide A2Mo3O8 as OER catalyst has been explored, the correlation between its active sites (tetrahedral or octahedral) and OER performance has been elusive. Now, magnetic Co2Mo3O8@NC-800 composed of highly crystallized Co2Mo3O8 nanosheets and ultrathin N-rich carbon layer is shown to be an efficient OER catalyst. The catalyst exhibits favorable performance with an overpotential of 331 mV@10 mA cm−2 and 422 mV@40 mA cm−2, and a full water-splitting electrolyzer with it as anode catalyst shows a cell voltage of 1.67 V@10 mA cm−2 in alkaline. Combined HAADFSTEM, magnetic, and computational results show that factors influencing the OER performance can be attributed to the tetrahedral Co sites (high spin, t23e4), which improve the OER kinetics of rate-determining step to form *OOH. 相似文献
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Ting Ouyang Xiao‐Tong Wang Xiu‐Qiong Mai An‐Na Chen Zi‐Yuan Tang Zhao‐Qing Liu 《Angewandte Chemie (International ed. in English)》2020,59(29):11948-11957
Transition‐metal oxides as electrocatalysts for the oxygen evolution reaction (OER) provide a promising route to face the energy and environmental crisis issues. Although palmeirite oxide A2Mo3O8 as OER catalyst has been explored, the correlation between its active sites (tetrahedral or octahedral) and OER performance has been elusive. Now, magnetic Co2Mo3O8@NC‐800 composed of highly crystallized Co2Mo3O8 nanosheets and ultrathin N‐rich carbon layer is shown to be an efficient OER catalyst. The catalyst exhibits favorable performance with an overpotential of 331 mV@10 mA cm?2 and 422 mV@40 mA cm?2, and a full water‐splitting electrolyzer with it as anode catalyst shows a cell voltage of 1.67 V@10 mA cm?2 in alkaline. Combined HAADFSTEM, magnetic, and computational results show that factors influencing the OER performance can be attributed to the tetrahedral Co sites (high spin, t23e4), which improve the OER kinetics of rate‐determining step to form *OOH. 相似文献
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A. L. Lapidus A. Yu. Krylova A. O. Kim Ya. M. Paushkin 《Russian Chemical Bulletin》1993,42(3):434-436
The activity and selectivity of 10 % Co/support and 10 % Ni/support catalysts (where the support is A12O3, SiO2, C) in the synthesis of hydrocarbons from CO2 and H2 were studied. The extent of conversion of the starting mixture and the yield of methane were shown to depend on the composition of the catalytic system. Cobalt catalysts with various types of carbons as supports are the most active. They permit the synthesis of methane in yields up to 70 % of the theoretical value.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 482–484, March, 1993. 相似文献
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Mengying Le Bingjie Hu Meiying Wu Huazhang Guo Liang Wang 《Molecules (Basel, Switzerland)》2022,27(15)
For the sake of the oxygen reduction reaction (ORR) catalytic performance, carbon dots (CDs) doped with metal atoms have accelerated their local electron flow for the past few years. However, the influence of CDs doped with metal atoms on binding sites and formation mechanisms is still uncertain. Herein, Co,N-doped CDs were facilely prepared by the low-temperature polymerization–solvent extraction strategy from EDTA-Co. The influence of Co doping on the catalytic performance of Co-CDs was explored, mainly in the following aspects: first, the pyridinic N atom content of Co-CDs significantly increased from 4.2 to 11.27 at% compared with the CDs, which indicates that the Co element in the precursor is advantageous in forming more pyridinic-N-active sites for boosting the ORR performance. Second, Co-CDs are uniformly distributed on the surface of carbon black (CB) to form Co-CDs@CB by the facile hydrothermal route, which can expose more active sites than the aggregation status. Third, the highest graphite N content of Co-CDs@CB was found, by limiting the current density of the catalyst towards the ORR. Composite nanomaterials formed by Co and CB are also used as air electrodes to manufacture high-performance zinc–air batteries. The battery has good cycle stability and realizes stable charges and discharges under different current densities. The outstanding catalytic activity of Co-CDs@CB is attributed to the Co,N synergistic effect induced by Co doping, which pioneer a new metal doping mechanism for gaining high-performance electrocatalysts. 相似文献
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Plasma‐Engraved Co3O4 Nanosheets with Oxygen Vacancies and High Surface Area for the Oxygen Evolution Reaction 下载免费PDF全文
Lei Xu Qianqian Jiang Zhaohui Xiao Xingyue Li Jia Huo Prof. Shuangyin Wang Prof. Liming Dai 《Angewandte Chemie (International ed. in English)》2016,55(17):5277-5281
Co3O4, which is of mixed valences Co2+ and Co3+, has been extensively investigated as an efficient electrocatalyst for the oxygen evolution reaction (OER). The proper control of Co2+/Co3+ ratio in Co3O4 could lead to modifications on its electronic and thus catalytic properties. Herein, we designed an efficient Co3O4‐based OER electrocatalyst by a plasma‐engraving strategy, which not only produced higher surface area, but also generated oxygen vacancies on Co3O4 surface with more Co2+ formed. The increased surface area ensures the Co3O4 has more sites for OER, and generated oxygen vacancies on Co3O4 surface improve the electronic conductivity and create more active defects for OER. Compared to pristine Co3O4, the engraved Co3O4 exhibits a much higher current density and a lower onset potential. The specific activity of the plasma‐engraved Co3O4 nanosheets (0.055 mA cm?2BET at 1.6 V) is 10 times higher than that of pristine Co3O4, which is contributed by the surface oxygen vacancies. 相似文献
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Identification of the Active Sites for Low Temperature CO Oxidation over Nanocrystalline Co3O4 Catalysts 下载免费PDF全文
The microstructural properties of dry‐grinding derived Co3O4 catalysts pretreated under different atmospheres, in relation to the activities on CO oxidation were investigated. The Co3O4 synthesized by soft reactive grinding and pretreated with O2 resulted in the best activity, with 100% conversion of CO at ?52 °C, superior to that of Co3O4 pretreated with He. To find out the active sites on Co3O4 for low temperature CO oxidation, the characterizations of the cobalt oxides had been investigated by means of N2 physisorption, XRD, TEM, H2‐TPR, CO‐titration, XPS and O2‐TPD technologies. XPS of Co2p results show that it is difficult to ascribe the difference in catalytic performance to the surface concentration of active Co3+ sites. A correlation between the activity and the CO‐titration and O2‐TPD results for Co3O4 reveals that a high abundance of readily accessible superficial electrophilic oxygen (O?) species is important for achieving a high activity. Therefore, CO oxidation takes place on the surface active oxygen sites in Co3O4 crystallites via the suprafacial mechanism. 相似文献
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采用液相沉淀法制备了Co3O4催化剂,用XRD、IR、TEM、CO滴定等表征技术和连续流动微反装置,考察了焙烧温度对Co3O4催化剂结构和催化性能的影响.结果表明,在研究的温度范围内催化剂均以单一的尖晶石结构存在,具有良好的CO氧化催化活性,经300℃焙烧的催化剂具有高的分散状态,有利于活性氧物种的形成和反应,在空速5000 h-1,CO体积分数0.5%的反应条件下常温可将CO完全转化500 min.焙烧温度高于或低于300℃均引起常温CO氧化性能的下降.通过对催化剂的抗水性试验和失活前后的XPS表征发现,催化剂的活性下降不是由于Co的价态变化引起的,而是由于水蒸气中毒. 相似文献