共查询到15条相似文献,搜索用时 78 毫秒
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单原子催化剂(SACs)以其最大的金属原子利用率和较高的催化活性而备受关注.本文提出了在Mn负载g-C3N4单层(Mn/g-C3N4)中进行B掺杂的方案来提升单原子催化剂的光催化活性,并利用第一性原理对Mn/B-g-C3N4单原子催化剂的晶体结构,电子结构,带边位置和光学性质进行计算.计算结果表明B掺杂具有较强的结构稳定性,带隙变小,同时带隙中出现杂质能级,导致吸收边向可见光区发生红移,提高了g-C3N4在太阳光下光吸收能力和光催化活性,研究结果为制备高效的g-C3N4基光催化SACs提供了理论指导. 相似文献
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用于HCOOH分解制氢的贵金属催化剂存在着反应选择性差和资源稀缺等问题. 单原子催化可以有效改善催化剂性能并降低成本,C2N作为一种新型二维材料可为过渡金属原子提供良好的结合位点. 本文利用密度泛函理论,设计了Pd@C2N 单原子催化剂,研究了HCOOH在Pd@C2N表面上的吸附和分解制氢反应机理. 结果表明,HCOOH可在Pd原子顶位吸附,并在C2N表面N原子的协同作用下通过甲酸盐路径生成氢气. 通过比较,Pd@C2N具有比Pd (111)表面更好的催化反应活性与选择性. 相似文献
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甲烷在金属氧化物上催化脱氢的从头计算 总被引:3,自引:0,他引:3
用G94的从头计算方法对甲烷在金属氧化镁及氧化锂表面上不同氧物种O^-,O^2-2,O^-2,O^2-催化脱氢进行了理论研究,确定了过渡态的几何构型,集居分布和反应活化能。结果表明,氧物种的催化脱氢的活性顺序为O^2-2≈O^-〉O^-2〉O^2-。其中O^-2物种由于对甲烷具有较低的氧化能力而可能是OCM活性和高C2选择性的氧物种。 相似文献
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本文研究了氧化石墨烯负载Pt单原子(Pt1/Gr-O)催化硼胺烷(NH3BH3)全水解反应机理,即一分子的NH3BH3生成三分子的氢气(H2)的过程. 在水解路径中,首先吸附的硼胺烷连续断裂两个B-H键生成第一分子的H2. 接着,一个H2O分子与*BHNH3基团(*表示吸附态)反应生成*BH(H2O)NH3,其中伸长的O-H键断裂后形成*BH(OH)NH3. 然后,第二个H2O与*BH(OH)NH3反应生成*BH(OH)(H2O)NH3,在指向Pt1/Gr-O表面的O-H断裂后,生成BH(OH)2NH3并脱附到水溶液中. 两个水分子脱氢产生的两个H原子脱附生成第二个H2分子,且Pt1/Gr-O催化剂恢复. 脱附后的BH(OH)2NH3在水溶液中水解生成第三个H2分子. 纵观整个水解反应,H2O分子和*BHNH3基团的结合是反应速控步,其反应能垒是16.1 kcal/mol. 因此,Pt1/Gr-O有希望成为室温催化NH3BH3全水解催化剂. 相似文献
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利用密度泛函理论,在slab模型下,研究N_2在单原子催化剂Ir_1/MoS_2上的吸附行为,结果表明,N_2的优势吸附位为Ir原子的顶位,构型为垂直向下,吸附能达到1.57 eV,是化学吸附.电子结构说明主要是吸附N原子的2Pz轨道在Z方向上与Ir的5d_z~2、5d_(xz)、5d_(yz)、6P_z混合得以使N_2稳定吸附在Ir原子上. 相似文献
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二氧化钛载体包括二氧化钛纳米管阵列(TNTAs)和二氧化钛纳米线阵列(TNWAs)两种,载体的结构不同对催化性能有一定的影响。然而,Pt负载在TNTAs和TNWAs催化性能的比较鲜有报道。本文通过微波法制备了Pt/TNTAs和Pt/TNWAs两种催化剂,结果表明,Pt/TNTAs催化甲醇氧化效果要优于Pt/TNWAs。相较于Pt/TNWAs, Pt/TNTAs的优越催化性能可能与纳米管的限域效应有关。可见,载体的结构对催化剂的性能有很大的影响。 相似文献
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利用R-矩阵方法计算了N原子基态在光子能量为1-3Ry范围内的光电离截面,给出了自电离态2s2p3(5S'0)np4P(n=3~10)的共振能量,我们的结果与已有的多组态Hartree-Fock理论计算(MCHF)及最近的实验结果相比符合得很好. 相似文献
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基于第一性原理计算方法,对含空位缺陷的V2C(MXene)在不同位点修饰单原子Al的相关性能进行系统研究.研究表明,几何优化后得到含空位缺陷的V2C稳定结构表面能为-3075.53 J/m2,单原子Al修饰本征V2C单原子的吸附能为1.5511eV、单原子Al修饰空位缺陷V2C的吸附能为-2.0763 eV,这表明含空位缺陷的V2C,由于单原子Al的修饰可以明显改善晶体结构稳定性.进一步从态密度、分波态密度、吸氢能力研究发现,各体系态密度和分波态密度均出现分波越过费米能级的现象,表现出较强的金属性;V2C吸附H2气体分子吸附能为-7.5867 eV,而空位缺陷V2C和单原子Al修饰空位缺陷V2C两个体系对H2气体分子的吸附能仅为-0.9851 eV、-2.7130 eV,均未能进一步改善V2C对H2气体分... 相似文献
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ABSTRACTThe stable configurations, electronic structures and catalytic activities of single-atom metal catalyst anchored silicon-doped graphene sheets (3Si-graphene-M, M?=?Ni and Pd) are investigated by using density functional theory calculations. Firstly, the adsorption stability and electronic property of different gas reactants (O2, CO, 2CO, CO/O2) on 3Si-graphene-M substrates are comparably analysed. It is found that the coadsorption of O2/CO or 2CO molecules is more stable than that of the isolated O2 or CO molecule. Meanwhile, the adsorbed species on 3Si-graphene-Ni sheet are more stable than those on the 3Si-graphene-Pd sheet. Secondly, the possible CO oxidation reactions on the 3Si-graphene-M are investigated through Eley–Rideal (ER), Langmuir–Hinshelwood (LH) and new termolecular Eley–Rideal (TER) mechanisms. Compared with the LH and TER mechanisms, the interaction between 2CO and O2 molecules (O2?+?CO → CO3, CO3?+?CO → 2CO2) through ER reactions (< 0.2?eV) are an energetically more favourable. These results provide important reference for understanding the catalytic mechanism for CO oxidation on graphene-based catalyst. 相似文献
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在燃烧后气体中选择性捕获CO2,对减缓因CO2浓度过高引发的环境问题具有十分重要的意义。本文采用第一性原理计算的方法,研究了外加电场作用下S修饰C24N24富勒烯对CO2的选择性吸附性能。首先研究了S@C24N24的结构和性质,发现其具有良好的稳定性。其次,研究了无电场时S修饰C24N24富勒烯对CO2的吸附行为,发现其吸附为弱的物理吸附。另外,进一步研究了外加电场作用下S@C24N24对CO2的吸附行为。结果表明,结合距离(CO2与S)和CO2的键角(O=C=O)随电场的增大而减小;当电场增加到0.018 au时,物理吸附转变为化学吸附。关闭电场时,化学吸附又转化为物理吸附。此外,即使在相同的电场条件下,S修饰C24N24富勒烯对N2的吸附也为弱的物理吸附。这表明,通过控制外加电场的开/关,S@C24N24可以从CO2/N2混合气体中选择性捕获/释放CO2,可作为选择性捕获CO2的优良候选材料。 相似文献
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In this work we perform DFT theoretical calculations of methane and steam interactions on Ni(1 1 1) surface. The calculations allow us to improve our understanding of the competition between these reactants by catalytic sites in methane steam reforming (MSR) process. For this purpose we compare theoretical results with kinetic measurements of MSR on a Ni(II)-Al(III) catalyst prepared from lamellar double hydroxides as precursor. This comparison shows that, for low H2O/CH4 ratios methane and water intermediate species adsorb on different catalytic sites. While CHO species adsorbs on top of Ni atom, OH one occupies preferentially a tri-coordinate surface site. On the other hand, for high H2O/CH4 ratios a competency between these species by Ni sites would establish, diminishing methane conversion. In addition competition between methane and steam for Ni sites would lead to a decrease in CO production. Nevertheless, intermediate species adsorbed on different active sites would produce CO2, whatever the steam/methane ratio. Thus, it would be optimum steam concentration in hydrocarbon feed and active sites distribution on catalyst surface, which could maximize H2 production and minimize CO selectivity. The theoretical findings agree with kinetic measurements, which show that maximum methane conversion depends on steam partial pressure in the feed; whereas always, selectivity to CO2 increases and to CO diminishes. 相似文献
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Wang Geun Shim 《Applied Surface Science》2010,256(17):5566-865
The heterogeneous adsorption and catalytic oxidation of benzene, toluene and o-xylene (BTX) over the spent platinum catalyst supported on activated carbon (Pt/AC) as well as the chemically treated spent catalysts were studied to understand their catalytic and adsorption activities. Sulfuric aqueous acid solution (0.1N, H2SO4) was used to regenerate the spent Pt/AC catalyst. The physico-chemical properties of the catalysts in the spent and chemically treated states were analyzed by using nitrogen adsorption-desorption isotherm and elemental analysis (EDX). The gravimetric adsorption and the light-off curve analysis were employed to study the BTX adsorption and oxidation on the spent catalyst and its modified Pt/AC catalysts. The experimental results indicate that the spent Pt/AC catalyst treated with the H2SO4 aqueous solution has a higher toluene adsorption and conversion ability than that of the spent Pt/AC catalyst. A further studies of H2SO4 treated Pt/AC catalyst on their catalytic and heterogeneous adsorption behaviours for BTX revealed that the activity of the H2SO4 treated Pt/AC catalyst follows the sequence of benzene > toluene > o-xylene. The adsorption equilibrium isotherms of BTX on the H2SO4 treated Pt/AC were measured at different temperatures ranging from 120 to 180 °C. To correlate the equilibrium data and evaluate their adsorption affinity for BTX, the two sites localized Langmuir (L2m) isotherm model was employed. The heterogeneous surface feature of the H2SO4 treated Pt/AC was described in detail with the information obtained from the results of isosteric enthalpy of adsorption and adsorption energy distributions. Furthermore, the activity of H2SO4 treated Pt/AC about BTX was found to be directly related to the Henry's constant, isosteric enthalpy of adsorption and adsorption energy distribution functions. 相似文献
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Christoph Appel John Mantzaras Rolf Schaeren Rolf Bombach Andreas Inauen Niclas Tylli Markus Wolf Timothy Griffin Dieter Winkler Richard Carroni 《Proceedings of the Combustion Institute》2005,30(2):2509-2517
The partial catalytic oxidation of methane to synthesis gas over Rh/ZrO2 was investigated experimentally and numerically at fuel-to-air equivalence ratios of 2.5 and 4.0 and pressures of 4 and 6 bar. Experiments were performed in an optically accessible, laboratory-scale, channel-flow catalytic reactor and involved in situ one-dimensional Raman measurements of major species (CH4, O2, H2O, CO2, H2, CO, and N2) concentrations across the reactor boundary layer. The numerical model included a two-dimensional elliptic code with elementary homogeneous (gaseous) and heterogeneous (catalytic) chemical reaction schemes. Homogeneous ignition experiments and numerical predictions have validated the employed gas-phase reaction mechanism and have further delineated the reactor extent over which the contribution of the homogeneous reaction pathway was negligible. Over the reactor extent where oxygen was still available, the employed heterogeneous reaction scheme provided good agreement with the measured species concentrations, overpredicting only to a small degree the partial over the total oxidation route. In the oxygen-depleted zones of the reactor, however, the heterogeneous scheme overpredicted to a greater degree the impact of steam reforming and water gas shift reactions, resulting in higher computed hydrogen yields at the reactor exit. Additional experiments and predictions were carried out in a sub-scale gas-turbine honeycomb reactor, at operating conditions leading to oxygen breakthrough. The predictions again favored the partial over the total oxidation route. A modified heterogeneous scheme was proposed that provided very good agreement with measurements in the honeycomb reactor and in the oxygen-rich zones of the laboratory-scale reactor. The hydrogen produced during partial oxidation was partly re-adsorbed on the catalyst leading to superadiabatic surface temperatures, thus exemplifying the importance of proper thermal management in commercial reactors. 相似文献