共查询到20条相似文献，搜索用时 0 毫秒
1.
Single-atom catalysts have been touted as highly efficient catalysts, but the catalytic single-atom sites are unstable and tend to aggregate into nanoparticles during chemical reactions. In this study, we show that SiC monolayers are promising substrates for the development of highly stable single-atom catalysts (Pd1/SiC) within the density functional theory. In presence of a Si-vacancy, the diffusion barrier energy of a Pd1 atom embedded in the SiC monolayer is substantially enhanced from 2.3 to 7.8 eV, which is much higher than the reported diffusion barrier energies of graphene, boron nitride and defective MgO of the same catalytic system. Ab initio molecular dynamic calculations at 500 K also confirm the enhanced stability of Pd1/SiC monolayer (Si-vacancy) such that the Pd1 atom remains embedded in the vacancy. Additionally, the Pd1/SiC monolayer (Si-vacancy) catalysts show a ∼34 % reduction of activation barrier energy for CO oxidation as compared to pristine catalysts. This work implies that nanostructured SiC materials are promising substrates for the synthesis of highly stable single-atom catalysts. 相似文献
2.
Nilekar AU Greeley J Mavrikakis M 《Angewandte Chemie (International ed. in English)》2006,45(42):7046-7049
3.
Pannopard P Khongpracha P Warakulwit C Namuangruk S Probst M Limtrakul J 《Chemphyschem》2012,13(2):583-587
The catalytic activity of carbon nanotubes (CNTs) for the removal of greenhouse gases, like nitrous oxide (N(2)O), can be fine-tuned by metal doping. We modify the inert surfaces of CNTs with Sc, Ti and V transition metals in order to investigate their capability of converting N(2)O to N(2). The stable composite catalysts of Sc-, Ti- and V-doped (5,5)single-walled carbon nanotubes (SWCNTs), along with the unmodified one were investigated by periodic DFT calculations. Without metal doping, the N(2) O decomposition on the bare tube proceeds over a high energy barrier (54.3 kcal mol(-1)) which in the presence of active metals is reduced to 3.6, 8.0 and 10.2 kcal mol(-1) for V-, Ti- and Sc-doped (5,5)SWCNTs, respectively. The superior reactivity is a result of the facilitated electron transfer between the tube and N(2)O caused by the overlap between the d orbitals of the metal and the p orbitals of N(2)O. 相似文献
4.
Wang HF Kavanagh R Guo YL Guo Y Lu GZ Hu P 《Angewandte Chemie (International ed. in English)》2012,51(27):6657-6661
5.
6.
Iron-nitrogen-carbon materials have been known as the most promising non-noble metal catalyst for proton-exchange membrane fuel cells (PEMFCs), but the genuine active sites for oxygen reduction reaction (ORR) are still arguable. Herein, by the thorough density functional theory investigations, we unravel that the planar Fe2N6 site exhibits excellent ORR catalytic activity over both FeN3 and FeN4 sites, and the potential-determining step is determined to be the *OH hydrogenation step with an overpotential of 0.415 V. The ORR activity of Fe2N6 site originates from the low spin magnetic moment (1.11 μB), which leads to high antibonding states and low d-band center of the Fe center, further leads to weak binding strength of *OH species. The density of FeN4 sites only has little influence on the ORR activity owing to the similar interaction between active site and intermediates in ORR. Our research sheds light on the activity origin of iron-nitrogen-carbon materials for ORR. 相似文献
7.
Shunlian Ning Zhiwei Guo Dr. Jigang Wang Prof. Shaobin Huang Prof. Shaowei Chen Prof. Xiongwu Kang 《ChemElectroChem》2021,8(14):2680-2685
Electrochemical reduction of carbon dioxide to formate provides an effective way to solve the environmental problems caused by excessive carbon dioxide emissions and produce value-added products. Herein, we report the preparation of a Sn-doped CeO2 catalyst, where oxygen vacancies are formed by thermal treatment in Ar/H2 atmosphere, leading to enhanced carbon dioxide electroreduction to formate. The Faraday efficiency of formate production is found to reach 81.10 %, with a geometric current density of 9.13 mA cm−2 at a potential of −1.10 V versus reversible hydrogen electrode. Density functional theory calculations show that the incorporation of tin into CeO2 promotes electron transport, lowers the energy barrier to form formate through HCOO*, and increases the selectivity of formate. Results from this study highlight the importance of metal-doping in CeO2 towards the selective reduction of CO2 to formate. 相似文献
8.
燃料电池的阴极反应的反应动力学速率非常慢,限制了燃料电池技术的发展。因此,寻找低成本、高活性的氧还原催化剂具有重要的意义。多元金属核壳团簇表现出优良的氧还原活性。在本文中,以原子个数为19、38、55和79的八面体团簇作催化剂模型,采用密度泛函理论(GGA-PBE-PAW)方法,研究了一系列不同尺寸核壳Nim@Mn-m (n = 19, 38, 55, 79;m = 1, 6, 13, 19; M = Pt, Pd, Cu, Au, Ag)团簇催化剂的活性规律。优化*O、*OH和*OOH吸附中间体结构,计算了吸附自由能和反应吉布斯自由能,以超电势为催化活性的描述符,研究了单原子Pt嵌入Nim@Aun-m团簇的活性规律。结果表明,Ni6@Pt1Au31具有最好的ORR活性,并且Ni1@Pt1Au17、Ni6@Pt1Au31、Ni13@Pt1Au41、Ni19@Pt1Au5表现出比Pt38团簇以及Pt(111)表面更高的催化活性。Bader电荷和态密度分析表面,核壳之间的电荷转移以及单原子Pt嵌入Nim@Aun-m表面,改变了吸附位的电子性质,降低了*OH的吸附强度,提高了ORR活性。单原子Pt嵌入Nim@Aun-m表面可能是一种合适的多元金属核壳ORR催化剂设计策略。 相似文献
9.
Dr. Jiafang Xie Xiaotao Zhao Prof. Maoxiang Wu Prof. Qiaohong Li Prof. Yaobing Wang Prof. Jiannian Yao 《Angewandte Chemie (International ed. in English)》2018,57(31):9640-9644
The electrochemical CO2 reduction (ECDRR), as a key reaction in artificial photosynthesis to implement renewable energy conversion/storage, has been inhibited by the low efficiency and high costs of the electrocatalysts. Herein, we synthesize a fluorine‐doped carbon (FC) catalyst by pyrolyzing commercial BP 2000 with a fluorine source, enabling a highly selective CO2‐to‐CO conversion with a maximum Faradaic efficiency of 90 % at a low overpotential of 510 mV and a small Tafel slope of 81 mV dec?1, outcompeting current metal‐free catalysts. Moreover, the higher partial current density of CO and lower partial current density of H2 on FC relative to pristine carbon suggest an enhanced inherent activity towards ECDRR as well as a suppressed hydrogen evolution by fluorine doping. Fluorine doping activates the neighbor carbon atoms and facilitates the stabilization of the key intermediate COOH* on the fluorine‐doped carbon material, which are also blocked for competing hydrogen evolution, resulting in superior CO2‐to‐CO conversion. 相似文献
10.
Lei Ji Lei Li Xuqiang Ji Ya Zhang Shiyong Mou Tongwei Wu Qian Liu Baihai Li Xiaojuan Zhu Yonglan Luo Xifeng Shi Abdullah M. Asiri Xuping Sun 《Angewandte Chemie (International ed. in English)》2020,59(2):758-762
Electrochemical reduction of CO2 into various chemicals and fuels provides an attractive pathway for environmental and energy sustainability. It is now shown that a FeP nanoarray on Ti mesh (FeP NA/TM) acts as an efficient 3D catalyst electrode for the CO2 reduction reaction to convert CO2 into alcohols with high selectivity. In 0.5 m KHCO3, such FeP NA/TM is capable of achieving a high Faradaic efficiency (FE ) up to 80.2 %, with a total FE of 94.3 % at ?0.20 V vs. reversible hydrogen electrode. Density functional theory calculations reveal that the FeP(211) surface significantly promotes the adsorption and reduction of CO2 toward CH3OH owing to the synergistic effect of two adjacent Fe atoms, and the potential‐determining step is the hydrogenation process of *CO. 相似文献
11.
Transition metal- and nitrogen-codoped graphene (referred to as M−N−G, where M is a transition metal) has emerged as an important type of single-atom catalysts with high selectivities and activities for electrochemical CO2 reduction (CO2R) to CO. However, despite extensive previous studies on the catalytic origin, the active site in M−N−G catalysts remains puzzling. In this study, density functional theory calculations and computational hydrogen electrode model is used to investigate CO2R reaction energies on Zn−N−G, which exhibits outstanding catalytic performance, and to examine kinetic barriers of reduction reactions by using the climbing image nudged elastic band method. We find that single Zn atoms binding to N and C atoms in divacancy sites of graphene cannot serve as active sites to enable CO production, owing to *OCHO formation (* denotes an adsorbate) at an initial protonation process. This contradicts the widely accepted CO2R mechanism whereby single metal atoms are considered catalytic sites. In contrast, the C atom that is the nearest neighbor of the single Zn atom (CNN) is found to be highly active and the Zn atom plays a role as an enhancer of the catalytic activity of the CNN. Detailed analysis of the CO2R pathway to CO on the CNN site reveals that *COOH is favorably formed at an initial electrochemical step, and every reaction step becomes downhill in energy at small applied potentials of about −0.3 V with respect to reversible hydrogen electrode. Electronic structure analysis is also used to elucidate the origin of the CO2R activity of the CNN site. 相似文献
12.
13.
Solar-driven conversion of CO2 with H-terminated silicon has recently attracted increasing interest. However, the molecular mechanism of the reaction is still not well understood. A systematic study of the mechanism has been carried out with first-principles calculations. The formation energies of the intermediates are found to be insensitive to the structure of the surface. On the fully H-terminated Si(111) surface, several pathways for the conversion of CO2 into CO at a coordinatively saturated Si site are studied, including the conventional COOH* pathway and the direct insertion of CO2 into Si−H and Si−Si bonds. Although the barrier of the COOH* pathway is lowest among the three pathways, it is higher than that for OH* elimination, which suggests that CO2 should be converted by other types of active site. The reaction at the isolated and dual coordinatively unsaturated (CUS) Si sites, which can be generated by light illumination, heat, and Pd loading, are then studied. The results suggest that the most efficient pathway to convert CO2 is to convert it into CO and O* at an isolated CUS Si site before O* reacts with a terminating H* to form adsorbed OH* and generate new isolated CUS Si sites. Therefore, the CUS Si site catalyzes the reaction until all H* is converted into OH*. The results provide new insight into the mechanism of the reaction and should be helpful for the design of more efficient Si-based catalysts for CO2 conversion. 相似文献
14.
The nature of a Rh single-atom catalyst (SAC) stabilized on the surface of tetragonal zirconia, t-ZrO2, is investigated here by performing extensive DFT calculations on various possible structural models and comparing the resulting spectral properties with existing data from the literature. The models considered include a Rh atom adsorbed on the clean surface, (Rh)ads, Rh atoms stabilized by the reaction with surface OH groups to form direct Rh−O bonds, (RhO)ads, and (RhO2)ads, the interaction of a Rh atom with an OH group, (RhOH)ads, and a Rh atom replacing Zr in the lattice, (Rh)subZr. Also a t-ZrO2 supported Rh6 cluster has been considered for comparison with Rh single atoms. Surface heterogeneity has been taken into account by computing the various Rh species at terraces and at step sites of the zirconia surface. Based on the calculated adsorption energies, Rh 3d core level binding energies, and stretching frequencies of adsorbed CO and comparison with the experimental data we conclude that the potential candidates for Rh SAC on t-ZrO2 are (RhO)ads and (RhOH)ads species. 相似文献
15.
16.
17.
Mengnan Qu Shaohua Xu Prof. Aijun Du Prof. Chongjun Zhao Prof. Qiao Sun 《Chemphyschem》2021,22(23):2392-2400
Designing high-performance materials for CO2 capture and conversion is of great significance to reduce the greenhouse effect and alleviate the energy crisis. The strategy of doping is widely used to improve activity and selectivity of the materials. However, it is unclear how the doping densities influence the materials’ properties. Herein, we investigated the mechanism of CO2 capture, separation and conversion on MoS2, MoSe2 and Janus MoSSe monolayers with different boron doping levels using density functional theory (DFT) simulations. The results indicate that CO2, H2 and CH4 bind weakly to the monolayers without and with single-atom boron doping, rendering these materials unsuitable for CO2 capture from gas mixtures. In contrast, CO2 binds strongly to monolayers doped with diatomic boron, whereas H2 and CH4 can only form weak interactions with these surfaces. Thus, the monolayers doped with diatomic boron can efficiently capture and separate CO2 from such gas mixtures. The electronic structure analysis demonstrates that monolayers doped with diatomic doped are more prone to donating electrons to CO2 than those with single-atom boron doped, leading to activation of CO2. The results further indicate that CO2 can be converted to CH4 on diatomic boron doped catalysts, and MoSSe is the most efficient of the surfaces studied for CO2 capture, separation and conversion. In summary, the study provides evidence for the doping density is vital to design materials with particular functions. 相似文献
18.
Mercero JM Matxain JM Ugalde JM 《Angewandte Chemie (International ed. in English)》2004,43(41):5485-5488
19.
Dr. Jürgen Bauer Prof. Dr. Holger Braunschweig Dr. Rian D. Dewhurst Dr. Krzysztof Radacki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(27):8797-8805
We herein report detailed investigations into the interaction of Lewis acidic fluoroboranes, for example BF2Pf (Pf=perfluorophenyl) and BF2ArF (ArF=3,5‐bis(trifluoromethyl)phenyl), with Lewis basic platinum complexes such as [Pt(PEt3)3] and [Pt(PCy3)2] (Cy=cyclohexyl). Two presumed Lewis adducts could be identified in solution and corresponding secondary products of these Lewis adducts were characterized in the solid state. Furthermore, the concept of frustrated Lewis pairs (FLP) was applied to the activation of ethene in the system [Pt(BPf3)(CH2CH2)(dcpp)] (dcpp=1,3‐bis(dicyclohexylphosphino)propane; Pf=perfluorophenyl). Finally, DFT calculations were performed to determine the interaction between the platinum‐centered Lewis bases and the boron‐centered Lewis acids. Additionally, several possible mechanisms for the oxidative addition of the boranes BF3, BCl3, and BF2ArF to the model complex [Pt(PMe3)2] are presented. 相似文献