Comparative Study of NO and CO Oxidation Reactions on Single-Atom Catalysts Anchored Graphene-like Monolayer

Noble metal single-atom catalysts (NM-SACs) anchored at novel graphene-like supports has attracted enormous interests. Gas sensitivity, catalytic activity, and d-band centers of single NM (Pt and Pd) atoms at graphenylene (graphenylene-NM) are investigated using first-principle calculations. The adsorption geometries of gas reactants on graphenylene-NM sheets are analyzed. It is found that the adsorption energies of reactant species on graphenylene-Pt are larger than those on graphenylene-Pd, because the d-band center of the Pt atom is closeser to the Fermi level. The NO and CO oxidation reactions on graphenylene-NM are investigated via four catalytic mechanisms, including Langmuir-Hinshelwood (LH), Eley-Rideal (ER), New ER (NER), and termolecular ER (TER). The results show that the NO and CO oxidations via LH and TER mechanisms can occur owing to the relatively small energy barriers. Moreover, the interaction of 2NO+2CO via ER mechanism is the energetically more favorable reaction. Although the NO oxidation via the NER mechanism has rather low energy barriers, the reaction is unlikely to occur due to the low adsorption energy of O₂ compared with CO and NO. This research may provide guidance for exploring the catalytic performance of SACs on graphene-like materials to remove toxic gas molecules.     

Stability and Catalytic Performance of Single-Atom Supported on Ti2CO2 for Low-Temperature CO Oxidation: A First-Principles Study

Based on first-principles calculations, the potential of Ti₂CO₂ monolayer (MXene) as a single-atom catalyst (SAC) support for 3d transition metal (TM) atoms (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) is studied for CO oxidation. We first screen the support effect according to the stability of a single metal atom and find that Sc and Ti supported on Ti₂CO₂ have stronger adsorption energy than the cohesive energy of their bulk counterparts and therefore, we selected Sc and Ti supported on Ti₂CO₂ for further catalytic reactions. The stability and the potential catalytic reactivity are verified by electronic structure and charge transfer analysis. Both Eley–Rideal (ER) and Langmuir–Hinshelwood (LH) mechanisms are considered in this study, and lower energy barriers of 0.002 and 0.37 eV were found in the ER mechanism compared to the LH mechanism, which are 0.25 and 0.34 eV for Sc and Ti catalysts, respectively. Moreover, kinetic ER and LH mechanisms are favorable for both Sc- and Ti/Ti₂CO₂ because of the comparable energy barrier to other metals and SAC supported on 2D materials. However, Ti/Ti₂CO₂ catalyst is thermodynamically unfavorable. Based on these calculations, we propose that Sc supported on Ti₂CO₂ is the best catalyst for CO-oxidation. The current study not only broadens the scope of the single-atom Sc catalyst but also extends the consideration of MXene support for catalyst optimization.     

单原子铂催化剂的制备及其低温催化氧化一氧化碳

以氧化石墨烯为载体,单原子铂（Pt）为活性组分,利用化学还原法制备了单原子Pt/rGO催化剂,用在催化氧化一氧化碳（CO）反应中。通过透射电子显微镜、扫描电子显微镜、球差电镜、傅里叶红外光谱仪对单原子Pt催化剂进行表征。考察了金属负载量、反应温度对催化剂性能的影响,利用气相色谱对CO氧化反应性能进行评价。此次实验包含催化剂的制备、表征和性能测试,实验难度适中,贴近科研前沿,可以让学生体验一个综合的科研过程,激发学生的科研兴趣,培养学生的科研能力。     

High‐Performance Ru1/CeO2 Single‐Atom Catalyst for CO Oxidation: A Computational Exploration

By means of density functional theory computations, we examine the stability and CO oxidation activity of single Ru on CeO₂(111), TiO₂(110) and Al₂O₃(001) surfaces. The heterogeneous system Ru₁/CeO₂ has very high stability, as indicated by the strong binding energies and high diffusion barriers of a single Ru atom on the ceria support, while the Ru atom is rather mobile on TiO₂(110) and Al₂O₃(001) surfaces and tends to form clusters, excluding these systems from having a high efficiency per Ru atom. The Ru₁/CeO₂ exhibits good catalytic activity for CO oxidation via the Langmuir–Hinshelwood mechanism, thus is a promising single‐atom catalyst.     

A Single-Atom Manipulation Approach for Synthesis of Atomically Mixed Nanoalloys as Efficient Catalysts

Synthesis of well-defined atomically mixed alloy nanoparticles on desired substrates is an ultimate goal for their practical application. Herein we report a general approach for preparing atomically mixed AuPt, AuPd, PtPd, AuPtPd NAs(nanoalloys) through single-atom level manipulation. By utilizing the ubiquitous tendency of aggregation of single atoms into nanoparticles at elevated temperatures, we have synthesized nanoalloys on a solid solvent with CeO₂ as a carrier and transition-metal single atoms as an intermediate state. The supported nanoalloys/CeO₂ with ultra-low noble metal content (containing 0.2 wt % Au and 0.2 wt % Pt) exhibit enhanced catalytic performance towards complete CO oxidation at room temperature and remarkable thermostability. This work provides a general strategy for facile and rapid synthesis of well-defined atomically mixed nanoalloys that can be applied for a range of emerging techniques.     

Nanoceria Supported Gold Catalysts for CO Oxidation

Two types of CeO₂ nanocubes (average size of 5 and 20 nm, respectively) prepared via the hydrothermal process were selected to load gold species via a deposition‐precipitation (DP) method. Various measurements, including X‐ray diffraction (XRD), Raman spectra, high resolution transmission electron microscopy (HRTEM), in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS), and temperature‐programmed reduction by hydrogen (H₂‐TPR), were applied to characterize the catalysts. It is found that the sample with ceria size of 20 nm (Au/CeO₂‐20) was covered by well dispersed both Au³⁺ and Au^δ+ (0 < δ < 1). For the other sample with ceria size of 5 nm (Au/CeO₂‐5), Au³⁺ is the dominant gold species. Au/CeO₂‐20 performed better catalytic activity for CO oxidation because of the strong CO adsorption of Au^δ+ in the catalysts. The catalytic activity of Au/CeO₂‐5 was improved due to the transformation of Au³⁺ to Au^δ+. Based on the CO oxidation and in situ DRIFTS results, Au^δ+ is likely to play a more important role in catalyzing CO oxidation reaction.     

Synergistic Effect of Boron Nitride and Carbon Domains in Boron Carbide Nitride Nanotube Supported Single-Atom Catalysts for Efficient Nitrogen Fixation

Developing the low-cost and efficient single-atom catalysts (SACs) for nitrogen reduction reaction (NRR) is of great importance while remains as a great challenge. The catalytic activity, selectivity and durability are all fundamentally related to the elaborate coordination environment of SACs. Using first-principles calculations, we investigated the SACs with single transition metal (TM) atom supported on defective boron carbide nitride nanotubes (BCNTs) as NRR electrocatalysts. Our results suggest that boron-vacancy defects on BCNTs can strongly immobilize TM atoms with large enough binding energy and high thermal/structural stability. Importantly, the synergistic effect of boron nitride (BN) and carbon domains comes up with the modifications of the charge polarization of single-TM-atom active site and the electronic properties of material, which has been proven to be the essential key to promote N₂ adsorption, activation, and reduction. Specifically, six SACs (namely V, Mn, Fe, Mo, Ru, and W atoms embedded into defective BCNTs) can be used as promising candidates for NRR electrocatalysts as their NRR activity is higher than the state-of-the art Ru(0001) catalyst. In particular, single Mo atom supported on defective BCNTs with large tube diameter possesses the highest NRR activity while suppressing the competitive hydrogen evolution reaction, with a low limiting potential of −0.62 V via associative distal path. This work suggests new opportunities for driving NH₃ production by carbon-based single-atom electrocatalysts under ambient conditions.     

Pd/NaZSM-5负载型催化剂上CO完全氧化研究

采用浸渍法制备了一系列Pd/NaZSM-5负载型催化剂。考察了焙烧温度、反应温 度、Pd含量及预还原等对CO氧化性能的影响。结果表明：制备条件和反应条件对催 化活性均有较大影响,催化剂的活性随着焙烧温度的增加而降低,随反应温度及 Pd含量的增加而增加。XRD,TEM结果表明催化剂中Pd组分处于高分散状状;表面 XPS分析证实催化剂表面Pd物种PdO_2和PdO在反应过程中发生明显的表面化学变化 ,高价Pd物种随反应的进行逐步被CO还原为低价Pd物种,催化剂活性下降与Pd物种 被还原有关。H_2预还原作用也导致催化剂活性有所下降。     

Ag_2~-催化CO氧化反应机理的理论研究

用密度泛函理论B3LYP方法详细研究了Ag_2~-催化CO氧化反应的机理.计算结果表明,O2分子在Ag_2~-和Au_2~-上吸附能相差不大,而CO分子在Ag_2~-上吸附要比在Ag_2~-上弱得多.Ag_2~-催化CO氧化反应共有四条反应途径.最可能反应通道为CO插入Ag2O_2~-中的Ag—O键形成中间体[Ag—AgC(O—O)O]-,然后直接分解形成产物CO2和Ag2O-,或另一分子CO进攻中间体[Ag—AgC(O—O)O]-形成两分子产物CO2和Ag_2~-.在动力学上最难进行的反应通道为经历碳酸根双银中间体,需要克服约0.24eV的能垒.Ag_2~-催化CO氧化反应活性要高于Au_2~-.     

载体对负载PdO催化剂的CO氧化活性的影响

由于催化燃烧比传统的热力燃烧法有反应温度低和能量消耗低的优点，因而广泛用于挥发性有机物和CO的消除．把和铂是最常用的催化剂，但是载体对催化性能的影响很大【‘’‘］．本文制备了系列负载把催化剂，发现载体的性质对催化剂的CO氧化活性影响很大．本文所用载体为CeO。，TIO。，SnO。，AI。O。，ZAI。，ZSM－5和SIO。催化剂制备采用浸渍法，把负载量为5％（质量分数）．催化剂经120C烘干后，于650’C空气气氛焙烧4h制成．在常压固定床流动反应装置上考察催化剂的CO氧化活性，反应气组成为CO2．4％，O。1．2％，N。96．4…     

Dual Metal Active Sites in an Ir1/FeOx Single-Atom Catalyst: A Redox Mechanism for the Water-Gas Shift Reaction

Herein, we report a theoretical and experimental study of the water-gas shift (WGS) reaction on Ir₁/FeO_x single-atom catalysts. Water dissociates to OH* on the Ir₁ single atom and H* on the first-neighbour O atom bonded with a Fe site. The adsorbed CO on Ir₁ reacts with another adjacent O atom to produce CO₂, yielding an oxygen vacancy (O_vac). Then, the formation of H₂ becomes feasible due to migration of H from adsorbed OH* toward Ir₁ and its subsequent reaction with another H*. The interaction of Ir₁ and the second-neighbouring Fe species demonstrates a new WGS pathway featured by electron transfer at the active site from Fe³⁺−O⋅⋅⋅Ir²⁺−O_vac to Fe²⁺−O_vac⋅⋅⋅Ir³⁺−O with the involvement of O_vac. The redox mechanism for WGS reaction through a dual metal active site (DMAS) is different from the conventional associative mechanism with the formation of formate or carboxyl intermediates. The proposed new reaction mechanism is corroborated by the experimental results with Ir₁/FeO_x for sequential production of CO₂ and H₂.     

酸化膨润土负载金催化剂用于CO氧化

用盐酸和硫酸对膨润土（Ben）进行改性处理,采用浸渍法（IMP）、沉积-沉淀法（DP）和阳离子吸附法(CA)制备改性膨润土负载的金催化剂,以CO氧化作为探针反应对催化剂的催化性能进行了研究,采用BET、XRD、TEM和TPD等对催化剂进行表征。 结果表明,经过简单的酸处理后的膨润土比表面积和孔体积有了大幅度的提高,硫酸酸化的膨润土作为载体较之盐酸酸化土更容易得到活性较高的金催化剂,XRD粒径计算结果和TEM观察结果证明,硫酸酸化的膨润土作为载体相比盐酸酸化土可以得到Au颗粒度更小的催化剂。 不同制备方法中,阳离子吸附法能较好的将Au负载于膨润土载体上,得到小颗粒的金催化剂,且在吸附48 h、450 ℃焙烧、150 ℃下H2还原的预处理条件下得到的催化剂活性最好。     

Comprehensive Mechanism of CO2 Electroreduction on Non-Noble Metal Single-Atom Catalysts of Mo2CS2-MXene

In this work, a series of non-noble metal single-atom catalysts of Mo₂CS₂-MXene for CO₂ reduction were systematically investigated by well-defined density-functional-theory (DFT) calculations. It is found that nine types of transitional metal (TM) supported Mo₂CS₂ (TM-Mo₂CS₂) are very stable, while eight can effectively inhibit the competitive hydrogen evolution reaction (HER). After comprehensively comparing the changes of free energy for each pathway in CO₂ reduction reaction (CO₂RR), it is found that the products of TM-Mo₂CS₂ are not completely CH₄. Furthermore, Cr-, Fe-, Co- and Ni-Mo₂CS₂ are found to render excellent CO₂RR catalytic activity, and their limiting potentials are in the range of 0.245–0.304 V. In particular, Fe-Mo₂CS₂ with a nitrogenase-like structure has the lowest limiting potential and the highest electrocatalytic activity. Ab initio molecular dynamics (AIMD) simulations have also proven that these kinds of single-atom catalysts with robust performance could exist stably at room temperature. Therefore, these single TM atoms anchored on the surface of MXenes can be profiled as a promising catalyst for the electrochemical reduction of CO₂.     

Research Progress and Application of Single-Atom Catalysts: A Review

Due to excellent performance properties such as strong activity and high selectivity, single-atom catalysts have been widely used in various catalytic reactions. Exploring the application of single-atom catalysts and elucidating their reaction mechanism has become a hot area of research. This article first introduces the structure and characteristics of single-atom catalysts, and then reviews recent preparation methods, characterization techniques, and applications of single-atom catalysts, including their application potential in electrochemistry and photocatalytic reactions. Finally, application prospects and future development directions of single-atom catalysts are outlined.     

Al2O3/Au(111)反相催化剂在CO氧化反应中界面作用的理论研究

氧化物负载的金催化剂具有温和条件下优异的CO催化氧化活性。实验与理论计算表明,金与氧化物两相界面在催化反应过程中具有重要地位。反相催化剂提供了全新的角度以探究界面的重要地位。本文以Au（111）表面负载Al₂O₃团簇为反相催化剂模型,基于密度泛函理论,对催化剂模型的构型、界面性质以及O₂、CO的吸附与氧化进行了理论计算与研究。理论计算表明：电荷的迁移增强了Al₂O₃小团簇在Au（111）表面的附着,在催化剂金表面与氧化铝的两相界面位置,Au原子与Al原子的协同作用使得氧分子易于在界面位置吸附,并因此高度活化。对催化CO氧化反应路径,分别计算了缔合机理和解离机理不同路径,从活化能分析表明缔合机理比解离机理更可能发生。本文的工作揭示了反相催化剂催化CO氧化的活性本质,表明两相界面在金催化CO氧化中具有重要作用。     

Catalytic Potential of Post-Transition Metal Doped Graphene-Based Single-Atom Catalysts for the CO2 Electroreduction Reaction

Catalysts are required to ensure electrochemical reduction of CO₂ to fuels proceeds at industrially acceptable rates and yields. As such, highly active and selective catalysts must be developed. Herein, a density functional theory study of p-block element and noble metal doped graphene-based single-atom catalysts in two defect sites for the electrochemical reduction of CO₂ to CO and HCOOH is systematically undertaken. It is found that on all of the systems considered, the thermodynamic product is HCOOH. Pb/C₃, Pb/N₄ and Sn/C₃ are identified as having the lowest overpotential for HCOOH production while Al/C₃, Al/N₄, Au/C₃ and Ga/C₃ are identified as having the potential to form higher order products due to the strength of binding of adsorbed HCOOH.     

负载型金属CO氧化催化体系的研究进展

本文结合近年来我们的研究工作以及国内外相关研究，概述了负载型金属CO氧化催化体系的研究进展，并进一步展望了今后的研究、发展方向以及应用前景。     

Ligand Stabilized Ni1 Catalyst for Efficient CO Oxidation

Supported single transition metal (TM₁) catalysts have attracted broad attention in academia recently. Still, their corresponding reactivity and stability under reaction conditions are critical but have not well explored at the fundamental level. Herein, we use density functional theory calculation and ab initio molecular dynamics simulation to investigate the role of reactants and ligands on the reactivity and stability of graphitic carbon nitride (g-C₃N₄) supported Ni₁ for CO oxidation. We find out that supported bare Ni₁ atoms are only metastable on the surface and tend to diffuse into the interlayer of g-C₃N₄. Though Ni₁ is catalytically active at moderate temperatures, CO adsorption induced dimerization deactivates the catalyst. Hydroxyl groups not only are able to stabilize the supported Ni₁ atom, but also increase the reactivity by participating directly in the reaction. Our results provide valuable insights on improving the chemical stability of TM₁ by ligands without sacrificing the reactivity, which are helpful for the rational design of highly loaded atomically dispersed supported metal catalysts.