纳米碳材料非金属催化的研究进展

纳米碳材料直接作为催化剂的非金属碳催化是目前材料科学与催化领域的前沿方向之一.相对于传统金属催化剂,纳米碳材料催化剂具有高效环保、低能耗、耐腐蚀等优点.在烃类转化、化学品合成、能源催化等领域表现出优异的催化性能和发展潜力.综述了近年来纳米碳非金属催化研究的最新进展,主要包括新型纳米碳材料的表面性质、催化特性、反应机理和宏观制备等关键问题,并对纳米碳催化存在的挑战和前景进行了展望.     

基于单原子催化剂的光热催化转化：原理和应用

在以碳中和为目标的全球共识下,太阳能作为一种取之不竭用之不尽的绿色环保能源被认为是替代传统化石燃料最有潜力的方式。在各种太阳能转换技术中,光热催化不仅可以最大化利用太阳能,在光场和热场双重驱动力作用下,还可以显著提升化学反应速率,引起广泛的研究兴趣。以孤立的单个原子均匀分散在载体上形成的单原子催化剂具有100%原子利用率、优异的催化活性、热稳定性等优势。因此,将单原子催化剂应用于光热催化开始受到越来越多的关注。本综述介绍了光催化、热催化和光热催化的基本原理和特征,同时列举一些典型的例子。随后以不同载体作为分类标准,总结了单原子光热催化应用的前沿研究进展。最后,提出了该催化体系所面临的挑战和未来的发展方向。本文旨在全面了解单原子催化剂在太阳能驱动光热催化领域的研究现状并为未来发展提供可行的建议。     

Photothermal catalysis for CO2 conversion

The conversion of carbon dioxide into useful fuels or chemical feedstocks is of great importance for achieving carbon emission peak and carbon neutrality. The harvesting and conversion of solar energy will provide a sustainable and environmentally friendly energy source for human production and living. Very recently, photothermal catalysis has been proved to exhibit great advantages in reducing the reaction temperature, promoting the catalytic activity, and manipulating the reaction pathway in comparison with traditional thermal catalysis. In this review, we firstly introduced the fundamental mechanisms and categories of photothermal catalysis to understand the synergy or the difference between photochemical and thermochemical reaction pathways. Subsequently, the criteria and strategies for photothermal catalyst design are discussed in order to inspire the development of high-efficiency photothermal catalytic route by achieving intense absorption of broadband solar energy spectrum and high conversion capability of solar-to-heat. Recent progress in CO₂ reduction achieved by photothermal catalysis was summarized in terms of production types. In the end, the future challenges and perspectives of photothermal catalytic CO₂ reduction are presented. We hope that this review will not only deepen the understanding of photothermal catalysis, but also inspire the design, preparation and application of high-performance photothermal catalysts, aiming at alleviating non-renewable fossil energy consumption and carbon emissions for early carbon emission peak and carbon neutrality.     

Homogeneous molecular catalysis of the electrochemical reduction of N2O to N2: redox vs. chemical catalysis

Homogeneous electrochemical catalysis of N₂O reduction to N₂ is investigated with a series of organic catalysts and rhenium and manganese bipyridyl carbonyl complexes. An activation-driving force correlation is revealed with the organic species characteristic of a redox catalysis involving an outer-sphere electron transfer from the radical anions or dianions of the reduced catalyst to N₂O. Taking into account the previously estimated reorganization energy required to form the N₂O radical anions leads to an estimation of the N₂O/N₂O˙⁻ standard potential in acetonitrile electrolyte. The direct reduction of N₂O at a glassy carbon electrode follows the same quadratic activation driving force relationship. Our analysis reveals that the catalytic effect of the mediators is due to a smaller reorganization energy of the homogeneous electron transfer than that of the heterogeneous one. The physical effect of “spreading” electrons in the electrolyte is shown to be unfavorable for the homogeneous reduction. Importantly, we show that the reduction of N₂O by low valent rhenium and manganese bipyridyl carbonyl complexes is of a chemical nature, with an initial one-electron reduction process associated with a chemical reaction more efficient than the simple outer-sphere electron transfer process. This points to an inner-sphere mechanism possibly involving partial charge transfer from the low valent metal to the binding N₂O and emphasizes the differences between chemical and redox catalytic processes.

Homogeneous electrochemical catalysis of N₂O reduction to N₂ is investigated with a series of organic catalysts and rhenium and manganese bipyridyl carbonyl complexes.     

High Catalytic Activity of Nitrogen and Sulfur Co‐Doped Nanoporous Graphene in the Hydrogen Evolution Reaction

Chemical doping has been demonstrated to be an effective way to realize new functions of graphene as metal‐free catalyst in energy‐related electrochemical reactions. Although efficient catalysis for the oxygen reduction reaction (ORR) has been achieved with doped graphene, its performance in the hydrogen evolution reaction (HER) is rather poor. In this study we report that nitrogen and sulfur co‐doping leads to high catalytic activity of nanoporous graphene in HER at low operating potential, comparable to the best Pt‐free HER catalyst, 2D MoS₂. The interplay between the chemical dopants and geometric lattice defects of the nanoporous graphene plays the fundamental role in the superior HER catalysis.     

Bifunctional Catalysts Containing Zn(II) and Imidazolium Salt Ionic Liquids for Chemical Fixation of Carbon Dioxide

Zn(II) can efficiently promote the catalytic performance of imidazolium salt ionic liquids (imi-ILs) for the chemical fixation of CO₂ into epoxides. To obtain sustainability, immobilized bifunctional catalysts containing both imi-ILs and Zn(II) were prepared using bimodal mesoporous silica (BMMs) as carrier, through grafting of Zn(OAc)₂ and 1-(trimethoxysilyl)propyl-3-methylimidazolium chloride (Si-imi) separately in the nanopores. The catalysts, named as BMMs−Zn&ILs, were identified as efficient catalysts for cycloaddition reaction of CO₂ into epoxides under solvent-free conditions. BMMs−Zn&ILs showed good catalytic activity, which increased with the increase of the molar ratio of Zn(II) to Si-imi. As a comparison, different catalytic systems including homogeneous imi-IL, BMMs-ILs and BMMs−Zn were studied to demonstrate different cooperation behaviors. Furthermore, the kinetics studies of homogeneous and heterogeneous bifunctional catalysts were employed to confirm the differences, as well as to support the proposed cooperative catalysis mechanism in the nanopores.     

应用于有机加氢反应的等离激元催化材料设计

金属纳米晶体具有独特的表面等离激元特性,为太阳能转换成化学能提供了新的机遇。本文以课题组近期的研究工作为例,阐述在催化有机加氢反应中表面等离激元效应所产生的多种物理过程的作用机制。该系列工作实现了太阳能向化学能的有效转换,为太阳能替代传统有机化工中的热催化提供了可能性,对等离激元催化材料的设计具有一定的指导意义。     

Bimodal Heterogeneous Functionality in Redox-Active Conjugated Microporous Polymer toward Electrocatalytic Oxygen Reduction and Photocatalytic Hydrogen Evolution

The designing and development of heterogeneous catalysts for conversion of renewable energy to chemical energies by electrochemical as well as photochemical processes is at the forefront of energy research. In this work, two new donor–acceptor-based redox-active conjugated microporous polymers (CMPs) (TAPA-OPE-mix and TAPA-OPE-gly) are synthesized through Schiff base condensation reaction using a microwave synthesizer. Notably, the asymmetric and symmetric bola-amphiphilic nature of the OPE struts results in distinct nanostructuring and morphologies in the CMPs. Interestingly, both CMPs show impressive heterogeneous catalytic activity toward electrochemical O₂ reduction and photocatalytic H₂ evolution reactions, and therefore, act as bimodal electro- and photocatalytic porous organic materials. Furthermore, the redox-active property of the CMPs is exploited for in situ generation and stabilization of platinum nanoparticles (Pt), and these Pt@CMPs exhibit significantly enhanced photocatalytic activity.     

在非平衡态热力学的基础上探索建立催化理的新途径

平衡态热力学一直被认作多相催化理论的基石之一。但是,它并不能概括工作中的催化剂的状态和行为,这主要是这里还发生一些非平衡过程。催化体系常常处于非平衡状态之下,而非平衡态条件下体系状态和行为,同时取决于体系的动力学和热力学。联系动力学和热力学最一般的关系式并非原来的De Donder不等式：Ar≥0,而是新的De Donde方程ln r^-/r^-=A/RT。同时发生的总反应之间的热力学耦合对总反应的作用只是形式上的,远不及催化反应链中各基元步骤之间在动力学上的耦合那么重要。通过在动力学方程中引入反应亲和力（热力学位）得到的动力学-热力学结合近似分析,可以用来分析非平衡态的催化反应和催化剂状态。非平衡态热力学在建立多相催化理论中,较之原来的平衡态热力学将能提供更能采纳的和更有意义的物理化学背景。     

Hot electron generation on metal catalysts under surface reaction: Principles,devices, and application

Transfer of charge through metal-support interfaces leads to an increase in the activity of mixed catalysts. In this review, we consider the main aspects of research aimed at studying processes that create and allow interphase transfer of highly excited (hot) charge carriers in supported catalysts, and discuss the effect of these phenomena on catalytic activity.     

Palladium versus Platinum: The Metal in the Catalytic Center of a Molecular Photocatalyst Determines the Mechanism of the Hydrogen Production with Visible Light

To develop highly efficient molecular photocatalysts for visible light‐driven hydrogen production, a thorough understanding of the photophysical and chemical processes in the photocatalyst is of vital importance. In this context, in situ X‐ray absorption spectroscopic (XAS) investigations show that the nature of the catalytically active metal center in a (N^N)MCl₂ (M=Pd or Pt) coordination sphere has a significant impact on the mechanism of the hydrogen formation. Pd as the catalytic center showed a substantially altered chemical environment and a formation of metal colloids during catalysis, whereas no changes of the coordination sphere were observed for Pt as catalytic center. The high stability of the Pt center was confirmed by chloride addition and mercury poisoning experiments. Thus, for Pt a fundamentally different catalytic mechanism without the involvement of colloids is confirmed.     

Noble metal-free hydrazine fuel cell catalysts: EPOC effect in competing chemical and electrochemical reaction pathways

We report the discovery of a highly active Ni-Co alloy electrocatalyst for the oxidation of hydrazine (N(2)H(4)) and provide evidence for competing electrochemical (faradaic) and chemical (nonfaradaic) reaction pathways. The electrochemical conversion of hydrazine on catalytic surfaces in fuel cells is of great scientific and technological interest, because it offers multiple redox states, complex reaction pathways, and significantly more favorable energy and power densities compared to hydrogen fuel. Structure-reactivity relations of a Ni(60)Co(40) alloy electrocatalyst are presented with a 6-fold increase in catalytic N(2)H(4) oxidation activity over today's benchmark catalysts. We further study the mechanistic pathways of the catalytic N(2)H(4) conversion as function of the applied electrode potential using differentially pumped electrochemical mass spectrometry (DEMS). At positive overpotentials, N(2)H(4) is electrooxidized into nitrogen consuming hydroxide ions, which is the fuel cell-relevant faradaic reaction pathway. In parallel, N(2)H(4) decomposes chemically into molecular nitrogen and hydrogen over a broad range of electrode potentials. The electroless chemical decomposition rate was controlled by the electrode potential, suggesting a rare example of a liquid-phase electrochemical promotion effect of a chemical catalytic reaction ("EPOC"). The coexisting electrocatalytic (faradaic) and heterogeneous catalytic (electroless, nonfaradaic) reaction pathways have important implications for the efficiency of hydrazine fuel cells.     

Methanol synthesis on ZnO(0001). III. Free energy landscapes, reaction pathways, and mechanistic insights

The interplay of physical and chemical processes in the heterogeneous catalytic synthesis of methanol on the ZnO(0001) surface with oxygen vacancies is expected to give rise to a complex free energy landscape. A manifold of intermediate species and reaction pathways has been proposed over the years for the reduction of CO on this catalyst at high temperature and pressure conditions as required in the industrial process. In the present study, the underlying complex reaction network from CO to methanol is generated in the first place by using ab initio metadynamics for computational heterogeneous catalysis. After having "synthesized" the previously discussed intermediates in addition to finding novel species, mechanistic insights into this network of surface chemical reactions are obtained based on exploring the global free energy landscape, which is refined by investigating individual reaction pathways. Furthermore, the impact of homolytic adsorption and desorption of hydrogen at the required reducing gas phase conditions is probed by studying such processes using different charge states of the F-center.     

Plasmonic heterogeneous catalysis for organic transformations

Plasmonic catalysis has been recognised as a promising alternative to many conventional thermal catalytic processes in organic synthesis. In addition to their high activity in fine chemical synthesis, plasmonic photocatalysts are also able to maintain control of selectivity under mild conditions by utilising visible-light as an energy source. This review provides an overview of the recent advances in organic transformations with plasmonic metal nanostructures, including selective reduction, selective oxidation, cross-coupling and addition reactions. We also summarize the photocatalysts and catalytic mechanisms involving surface plasmon resonance. Finally, control of reaction pathway and strategies for tailoring product selectivity in fine chemical synthesis are discussed.     

多相催化时空演变的全生命周期表征策略

可持续发展的化学工业需要新型高效的催化材料和催化过程,尤其需要生态友好、本质安全的新催化过程,其本质是提高合适反应器内催化剂的选择性、活性和稳定性.因此,通过原位技术实时表征反应状态下的催化剂结构并同步测试催化性能,有助于全面研究真实反应条件下催化剂及其表面物种随时间的演变过程,深入理解催化剂构效关系的本质,为开发新一代催化技术提供科学依据.迄今,在实际催化体系中实现催化剂从活化、运行到失活的全生命周期表征仍存在巨大挑战.本文综述了分子筛、金属、金属氧化物三类典型催化剂在甲醇制烯烃、费托合成、丙烷脱氢等催化反应中的全生命周期时空演变,分析了所采用的表征研究策略,以期为新型工业催化的应用基础研究提供启示.据文献报道,甲醇制烯烃反应案例主要利用了原位紫外-可见光谱和固态核磁共振光谱等获得SAPO-34分子筛催化剂从诱导期、自催化期到失活期的表面烃池物种性质和动态演变;费托合成反应案例主要利用了同步辐射X射线衍射计算机断层扫描和X射线吸收光谱等技术研究单个毫米级Co/γ-Al2O3催化剂颗粒在还原条件和费托合成条件下的催化剂结构演变;丙烷脱氢反应案例主要结合原位的紫外-可见和拉曼光纤探头分析了CrOx/Al2O3催化剂在700 ml固定床反应器中不同床层积炭的时空演变.这些研究案例表明,因受限于表征仪器的时空分辨率和适用工况,多数重要的催化反应尚未完全实现工业条件下的全生命周期表征;但通过合理简化非关键变量,可以获得近似工业条件下的多相催化时空演变规律,这些原位表征研究拓展了多相催化的新认识新发现.着眼未来,近似工业反应条件的原位表征、多尺度的原位表征装置设计、反应条件下的计算模拟等策略将在催化研发中发挥重要作用.这些全生命周期表征策略反映了催化研究范式的转变,但将其应用于工业实践仍面临许多科学和工程的挑战.从实际应用角度看,还需综合考虑原位表征技术的成本、安全性和准确性,重视催化剂颗粒及反应器尺度的原位表征,不断推进新型催化剂的研发.     

Gas-phase catalysis by atomic and cluster metal ions: the ultimate single-site catalysts

Gas-phase experiments with state-of-the-art techniques of mass spectrometry provide detailed insights into numerous elementary processes. The focus of this Review is on elementary reactions of ions that achieve complete catalytic cycles under thermal conditions. The examples chosen cover aspects of catalysis pertinent to areas as diverse as atmospheric chemistry and surface chemistry. We describe how transfer of oxygen atoms, bond activation, and coupling of fragments can be mediated by atomic or cluster metal ions. In some cases truly unexpected analogies of the idealized gas-phase ion catalysis can be drawn with related chemical transformations in solution or the solid state, and so improve our understanding of the intrinsic operation of a practical catalyst at a strictly molecular level.     

2020 roadmap on pore materials for energy and environmental applications

Porous materials have attracted great attention in energy and environment applications. In this roadmap, several porous materials are discussed for energy storage and conversion. It will help the researchers to obtain them guidance from it in future.     

Engineering Heterogeneous Catalysis with Strong Metal–Support Interactions: Characterization,Theory and Manipulation

Strong metal–support interactions (SMSI) represent a classic yet fast-growing area in catalysis research. The SMSI phenomenon results in the encapsulation and stabilization of metal nanoparticles (NPs) with the support material that significantly impacts the catalytic performance through regulation of the interfacial interactions. Engineering SMSI provides a promising approach to steer catalytic performance in various chemical processes, which serves as an effective tool to tackle energy and environmental challenges. Our Minireview covers characterization, theory, catalytic activity, dependence on the catalytic structure and inducing environment of SMSI phenomena. By providing an overview and outlook on the cutting-edge techniques in this multidisciplinary research field, we not only want to provide insights into the further exploitation of SMSI in catalysis, but we also hope to inspire rational designs and characterization in the broad field of material science and physical chemistry.     

基于过渡金属二硫族化物析氢催化的研究进展

解决全球气候变化和能源危机的有效途径之一是用氢能源(H₂)代替传统的化石能源. 析氢反应(Electrochemical hydrogen evolution reaction, HER) 被认为是绿色环保的可持续产氢途径, 通常电解过程需要催化剂以降低电化学电位, 提高能量利用效率. 目前最先进的催化剂仍然依赖于贵金属, 但是研究表明, 过渡金属二硫族化物(Transition metal dichalcogenides, TMDs)同样具有优异的催化活性, 与贵金属相比, TMDs产量大、 价格低、 催化活性好、 便于调控和修饰, 有望替代贵金属在催化领域的应用. 基于此, 本文讨论了近年来TMDs在析氢方面的研究情况以及TMDs材料的性能调控, 包含原子工程、 相工程和异质结. 并总结和展望了TMDs催化材料的挑战与机遇.