铂基金属间化合物纳米晶的最新进展:可控合成与电催化应用

铂基金属间化合物纳米晶因其高度有序的结构特点,优异的抗氧化及耐腐蚀性能,作为电极材料被广泛应用于各类电催化反应,目前已有的PtCo金属间化合物纳米晶在燃料电池阴极反应(氧还原反应)中的活性和稳定性均达到了美国能源部(DOE) 2020年的目标。为了进一步提高金属间化合物纳米晶的电催化性能,需要对影响纳米晶电催化性能的因素进行深入研究。本文综述了铂基金属间化合物纳米晶的研究现状,着重介绍了铂基金属间化合物的可控合成策略及其在电催化领域的最新研究进展,分析总结了该领域存在的问题,并展望了其未来发展方向。     

Integrated Bismuth Oxide Ultrathin Nanosheets/Carbon Foam Electrode for Highly Selective and Energy-Efficient Electrocatalytic Conversion of CO2 to HCOOH

Electroreduction of CO₂ into formic acid (HCOOH) is of particular interest as a hydrogen carrier and chemical feedstock. However, its conversion is limited by a high overpotential and low stability due to undesirable catalysts and electrode design. Herein, an integrated 3D bismuth oxide ultrathin nanosheets/carbon foam electrode is designed by a sponge effect and N-atom anchor for energy-efficient and selective electrocatalytic conversion of CO₂ to HCOOH for the first time. Benefitting from the unique 3D array foam architecture for highly efficient mass transfer, and optimized exposed active sites, as confirmed by density functional theory calculations, the integrated electrode achieves high electrocatalytic performance, including superior partial current density and faradaic efficiency (up to 94.1 %) at a moderate overpotential as well as a high energy conversion efficiency of 60.3 % and long-term durability.     

Metallic glasses and metallic glass nanostructures for functional electrocatalytic applications

This brief review reports the recent advancement of metallic glasses and metallic glass nanostructures for functional electrocatalytic applications. Metallic glasses（MGs） or amorphous metals result from quenching the melts at a high cooling rate（e.g.,10⁶K/s）, bypassing crystallization. Metallic glasses are devoid of long-range translational order, no defects like grain boundaries, and multiple elements included. Due to these unique structural features, MG s show distinct and valuable ...     

Electrocatalytic CO2 Reduction: from Discrete Molecular Catalysts to Their Integrated Catalytic Materials

Molecular catalysts (metal complexes), with molecularly defined uniform active sites and atomically precise structural tailorability allowing for regulating catalytic performance through metal- and ligand-centered engineering and elucidating reaction mechanisms via routine photoelectrochemical characterizations, have been increasingly explored for electrocatalytic CO₂ reduction (ECR). However, their poor stability and low catalytic current density are undesirable for practical applications. Heterogenizing discrete molecular catalysts can potentially surmount these issues, and the resulting integrated catalysts largely share catalytical properties with their discrete molecular counterparts, which bridge the gap between heterogeneous and homogeneous catalysis and combine their advantages. This minireview surveys advances in design and regulation of molecular catalysts such as porphyrin, phthalocyanine, and bipyridine-based metal complexes and their integrated catalytic materials for selective ECR.     

Electrocatalysis as the Nexus for Sustainable Renewable Energy: The Gordian Knot of Activity,Stability, and Selectivity

The use of renewable energy by means of electrochemical techniques by converting H₂O, CO₂ and N₂ into chemical energy sources and raw materials, is the basis for securing a future sustainable “green” energy supply. Some weaknesses and inconsistencies in the practice of determining the electrocatalytic performance, which prevents a rational bottom‐up catalyst design, are discussed. Large discrepancies in material properties as well as in electrocatalytic activity and stability become obvious when materials are tested under the conditions of their intended use as opposed to the usual laboratory conditions. They advocate for uniform activity/stability correlations under application‐relevant conditions, and the need for a clear representation of electrocatalytic performance by contextualization in terms of functional investigation or progress towards application is emphasized.     

Associative vs. dissociative mechanism: Electrocatalysis of nitric oxide to ammonia

Nitric oxide reduction to ammonia by electrocatalysis is the potential application in the elimination of smog and energy conversion. In this work, the feasibility of the application of two-dimensional metal borides(MBenes) in nitric oxide electroreduction reaction(NOER) was investigated through density functional theory calculations. Including the geometry and electronic structure of five kinds of MBenes, the adsorption of NO on the surface of these substrates, the selective adsorption of hydrog...     

Functional nanocomposites for energy storage: chemistry and new horizons

Energy storage devices are one of the hot spots in recent years due to the environmental problems caused by the large consumption of unsustainable energy such as petroleum or coal. Capacitors are a common device for energy storage, especially electrical energy. A variety of types including electrolytic capacitors, mica capacitors, paper capacitors, ceramic capacitors, film capacitors, and non-polarized capacitors have been proposed. Their specific applications depend on their intrinsic properties. Dielectric capacitors have reasonable energy storage density, with current research focusing on the enhancement of energy density and making the materials more flexible as well as lightweight. Improvement strategies are based on the premise that use of two or more different materials (e.g. polymers and ceramics/metals) at an optimal formulation can result in properties that combine the advantages of the precursor materials. Different polymers especially fluoropolymers (e.g. PVDF and PVDF based co-polymer) are the main components in dielectric nanocomposites for capacitors with high energy storage performance. In this article, we have briefly summarized the recent advances in functional polymers nanocomposites for energy storage applications with a primary focus on polymers, surface engineering, functional groups and novel synthesis/manufacturing concepts applied to new materials. The article presents a unique integrated structure and approaches providing key knowledge for the design and development of novel, low-cost, multifunctional next-generation energy storage materials with improved efficiency.     

导电金属有机框架材料在电催化中的成就，挑战和机遇

To fulfill the demands of green and sustainable energy, the production of novel catalysts for different energy conversion processes is critical. Owing to the intriguing advantages of the intrinsic active species, tunable crystal structure, remarkable chemical and physical properties, and good stability, metal-organic frameworks (MOFs) have been extensively investigated in various electrochemical energy conversions, such as the CO₂ reduction reaction, N₂ reduction reaction, oxygen evolution reaction, hydrogen evolution reaction, and oxygen reduction reaction. More importantly, it is feasible to change the chemical environments, pore sizes, and porosity of MOFs, which will theoretically facilitate the diffusion of reactants across the open porous networks, thereby improving the electrocatalytic performance. However, owing to the high energy barriers of charge transfer and limited free charge carriers, most MOFs show poor electrical conductivity, thus limiting their diverse applications. As reported previously, MOFs were used as a porous substrate to confine the growth of nanoparticles or co-doped electrocatalysts after annealing. The conductive MOFs can combine the advantages of conventional MOFs with electronic conductivity, which significantly enhance the electrocatalytic performance. In addition, conductive MOFs can achieve conductivity via electronic or ionic routes without post-annealing treatment, thereby extending their potential applications. Different synthesis strategies have recently been developed to endow MOFs with electrical conductivity, such as post-synthesis modification, guest molecule introduction, and composite formatting. The performance of conductive MOFs can even outperform those of commercial RuO₂ catalysts or Pt-group catalysts. However, it is difficult to endow most MOFs with high conductivity. This review summarizes the mechanisms of constructing conductive MOFs, such as redox hopping, through-bond pathways, through-space pathways, extended conjugation, and guest-promoted transport. Synthetic methods, including hydro/solvothermal synthesis and interface-assisted synthesis, are introduced. Recent advances in the use of conductive MOFs as heterogeneous catalysts in electrocatalysis have been comprehensively elucidated. It has been reported that conductive MOFs can demonstrate considerable catalytic activity, selectivity, and stability in different electrochemical reactions, revealing the immense potential for future displacement of Pt-group catalysts. Finally, the challenges and opportunities of conductive MOFs in electrocatalysis are discussed. Based on systematic synthesis strategies, more conductive MOFs can be constructed for electrocatalytic reactions. In addition, the morphology and structure of conductive MOFs, which can change the electrochemical accessibility between substrates and MOFs, are also crucial for catalysis, and thus, they should be extensively studied in the future. It is believed that a breakthrough for high-performance conductive MOF-based electrocatalysts could be achieved.     

Discovering Intermetallics Through Synthesis,Computation, and Data-Driven Analysis

Intermetallics adopt an array of crystal structures, boast diverse chemical compositions, and possess exotic physical properties that have led to a wide range of applications from the biomedical to aerospace industries. Despite a long history of intermetallic synthesis and crystal structure analysis, identifying new intermetallic phases has remained challenging due to the prolonged nature of experimental phase space searching or the need for fortuitous discovery. In this Minireview, new approaches that build on the traditional methods for materials synthesis and characterization are discussed with a specific focus on realizing novel intermetallics. Indeed, advances in the computational modeling of solids using density functional theory in combination with structure prediction algorithms have led to new high-pressure phases, functional intermetallics, and aided experimental efforts. Furthermore, the advent of data-centered methodologies has provided new opportunities to rapidly predict crystal structures, physical properties, and the existence of unknown compounds. Describing the research results for each of these examples in depth while also highlighting the numerous opportunities to merge traditional intermetallic synthesis and characterization with computation and informatics provides insight that is essential to advance the discovery of metal-rich solids.     

有机场效应材料氟化噻吩并四硫富瓦烯衍生物的电荷传输性质

噻吩并四硫富瓦烯(TTF)衍生物在有机场效应材料方面有较大的应用前景.应用密度泛函理论B3LYP泛函在6-31G(d,p)基组水平上计算了系列氟取代扩展噻吩并四硫富瓦烯衍生物(c2FT、t2FT及4FT)的轨道能级、电离能(IP)、电子亲和势(EA)和重组能(λ).在此基础上,进一步计算二聚体的迁移率,评估了载流子传输能力,并讨论取代位置和堆积方式对电荷传输性质的影响.计算结果表明,氟取代位置对二噻吩并四硫富瓦烯(DT-TTF)衍生物迁移率及电荷传输性质的影响较小,却有效降低了给电子能力.计算结果对设计和合成高效稳定的光电功能材料具有指导意义.     

碳基无金属电催化剂的本征缺陷研究进展

自首次报道氮掺杂碳纳米管具有优良的氧还原催化性能以来,碳基无金属材料作为贵金属基电催化剂的潜在替代品而被寄予厚望。碳骨架中普遍存在的本征缺陷位点是影响碳材料物理化学性质的重要因素。特定碳缺陷的引入可以打破原本完整的sp²碳骨架而形成局部畸变,改变邻近碳原子的电荷或自旋密度分布,进而优化催化过程反应物和中间产物的吸附/脱附,提升活性位点的催化活性。因此,在碳基材料中设计创造特定的缺陷结构成为了制备高活性电催化剂的重要研究方向。本文对近年来碳基无金属电催化剂中本征缺陷的研究进展进行了综述,归纳了碳材料中常见的3类本征缺陷（边界、空位或孔洞、拓扑畸变）的制备策略和表征手段,并深入讨论了不同类型碳缺陷的构型和电子结构与其电催化活性的内在关系。最后,我们对目前本征碳缺陷在电催化领域的研究挑战和未来前景进行了总结和展望。     

Phosphorescent platinum(II) complexes derived from multifunctional chromophores: synthesis, structures, photophysics, and electroluminescence

The synthesis and structural, photophysical, electrochemical, and electroluminescent properties of a novel class of trifunctional Pt(II) cyclometalated complexes are reported in which the hole-transporting triarylamine, electron-transporting oxadiazole, and electroluminescent metal components are integrated into a single molecule. These neutral metal chelates display good thermal stability (>250 degrees C under N2) and morphological stability. All of them exhibit intense ligand-centered fluorescence and phosphorescence in fluid solutions at room temperature, but the emission spectra become largely dominated by triplet emission bands in CH2Cl2 glass at 77 K. Substituents with different electronic properties were introduced into the bipolar cyclometalating ligands to fine-tune the absorption and emissive characteristics of the compounds, and the results were correlated with theoretical calculations using density functional theory. A comparison of the photophysics and electrochemistry of our multifunctional systems to those only derived from each of the constituent components was also made and discussed. These Pt complexes can be vacuum-sublimed and applied as emissive dopants for the fabrication of vapor-deposited electrophosphorescent organic light-emitting devices (OLEDs), which generally exhibit good device performance with efficiencies up to 3.6%, 11.0 cd A-1, and 5.8 lm W-1. While the electroluminescence energy resembles that recorded in fluid solutions for these Pt emitters, these monochromatic OLEDs can emit tunable colors by varying the aryl ring substituents and the level of doping. Saliently, single dopant white-light electroluminescence, triggered by the simultaneous fluorescence/phosphorescence emission of the metal complexes and a variation of applied driving voltages, has also been realized based on some of these multifunctional complexes with peak electrophosphorescence efficiencies of 6.8 cd A-1 and 2.6%.     

Thermochemical kinetics of hydrogen-atom transfers between methyl, methane, ethynyl, ethyne, and hydrogen

Saddle point properties of three symmetric and one asymmetric hydrogen transfer and the energy of reaction of the asymmetric reactions are investigated in the present work. These reactions were calculated by various density functionals, many of which were developed in recent years, by coupled cluster theory, and by multicoefficient correlation methods based on wave function theory. Instead of comparing calculated results to "semi-experimental" values, we compared them to very accurate theoretical values (e.g., to values obtained by the Weizmann-1 method). Coupled cluster theory and the multicoefficient correlation methods MC-QCISD/3 and MCQCISD-MPW are very accurate for these reactions with mean unsigned errors below 0.94 kcal/mol. Diagnostics for multireference character add additional reliability to these results. The newly developed hybrid density functional M06-2X shows very good performance for these reactions with a mean unsigned error of only 0.77 kcal/mol; the BHandHLYP, MPW1K, and BB1K density functionals, can also predict these reactions well with mean unsigned errors less than 1.42 kcal/mol.     

高效催化氧还原及氧析出反应的掺杂石墨炔的设计与理论计算

在清洁和可再生能源的转化过程中, 氧还原反应和氧析出反应需要高效的电催化剂以克服其动力学限制. 本文设计了一系列掺杂杂原子的无金属石墨二炔, 以促进上述两类关键化学反应.为了评估电催化性能, 利用密度泛函理论研究了反应路径和吉布斯自由能变化. 计算结果表明, 掺杂剂可以优化中间体的吸附, 降低反应的过电位. 本文还得到了将催化剂性质与催化剂结构相关联的内在描述符, 该描述符可以加速开发和筛选新型电催化剂. 研究结果可为清洁能源技术(如燃料电池、 金属空气电池和电解水等)中碳基催化剂的设计提供指导.     

General Synthesis of Single-Atom Catalysts for Hydrogen Evolution Reactions and Room-Temperature Na-S Batteries

Herein, we report a comprehensive strategy to synthesize a full range of single-atom metals on carbon matrix, including V, Mn, Fe, Co, Ni, Cu, Ge, Mo, Ru, Rh, Pd, Ag, In, Sn, W, Ir, Pt, Pb, and Bi. The extensive applications of various SACs are manifested via their ability to electro-catalyze typical hydrogen evolution reactions (HER) and conversion reactions in novel room-temperature sodium sulfur batteries (RT-Na-S). The enhanced performances for these electrochemical reactions arisen from the ability of different single active atoms on local structures to tune their electronic configuration. Significantly, the electrocatalytic behaviors of diverse SACs, assisted by density functional theory calculations, are systematically revealed by in situ synchrotron X-ray diffraction and in situ transmission electronic microscopy, providing a strategic library for the general synthesis and extensive applications of SACs in energy conversion and storage.     

Metal–Organic Frameworks-Derived Self-Supported Carbon-Based Composites for Electrocatalytic Water Splitting

Electrocatalytic water splitting has been considered as a promising strategy for the sustainable evolution of hydrogen energy and storage of intermittent electric energy. Efficient catalysts for electrocatalytic water splitting are urgently demanded to decrease the overpotentials and promote the sluggish reaction kinetics. Carbon-based composites, including heteroatom-doped carbon materials, metals/alloys@carbon composites, metal compounds@carbon composites, and atomically dispersed metal sites@carbon composites have been widely used as the catalysts due to their fascinating properties. However, these electrocatalysts are almost powdery form, and should be cast on the current collector by using the polymeric binder, which would result in the unsatisfied electrocatalytic performance. In comparison, a self-supported electrode architecture is highly attractive. Recently, self-supported metal–organic frameworks (MOFs) constructed by coordination of metal centers and organic ligands have been considered as suitable templates/precursors to construct free-standing carbon-based composites grown on conductive substrate. MOFs-derived carbon-based composites have various merits, such as the well-aligned array architecture and evenly distributed active sites, and easy functionalization with other species, which make them suitable alternatives to non-noble metal-included electrocatalysts. In this review, we intend to show the research progresses by employment of MOFs as precursors to prepare self-supported carbon-based composites. Focusing on these MOFs-derived carbon-based nanomaterials, the latest advances in their controllable synthesis, composition regulation, electrocatalytic performances in hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and overall water splitting (OWS) are presented. Finally, the challenges and perspectives are showed for the further developments of MOFs-derived self-supported carbon-based nanomaterials in electrocatalytic reactions.     

Developments in nanostructured LiMPO4 (M = Fe, Co, Ni, Mn) composites based on three dimensional carbon architecture

Nanostructured materials lie at the heart of fundamental advances in efficient energy storage and/or conversion, in which surface processes and transport kinetics play determining roles. This review describes recent developments in the synthesis and characterization of composites which consist of lithium metal phosphates (LiMPO(4), M = Fe, Co, Ni, Mn) coated on nanostructured carbon architectures (unordered and ordered carbon nanotubes, amorphous carbon, carbon foams). The major goal of this review is to highlight new progress in using different three dimensional nanostructured carbon architectures as support for the phosphate based cathode materials (e.g.: LiFePO(4), LiCoPO(4)) of high electronic conductivity to develop lithium batteries with high energy density, high rate capability and excellent cycling stability resulting from their huge surface area and short distance for mass and charge transport.     

Hydrogen electrocatalysis.

A selection of recent theoretical and experimental studies on electrolytic hydrogen evolution is presented. It is demonstrated with well-defined model surfaces that this reaction is a very structure-sensitive process. Crystallographic orientation, defect density and surface composition are parameters that determine the local geometric and electronic surface structure, and are thus crucial for the electrocatalytic activity as characterised by the exchange current density. The observed trends can be understood within a recent theory by J. K. N?rskov et al., which is based on density functional calculations and which emphasises the impact of hydrogen chemisorption energies on the reaction rate, that is, on the exchange current density. The particular electrocatalytic activities of ultrathin metal films and of nanostructures are addressed.     

Solid-State Conversion Synthesis of Advanced Electrocatalysts for Water Splitting

Electrolytic water technology is promising for sustainable energy utilization, but the lack of efficient electrocatalysts retards its application. The intrinsic activity of electrocatalysts is determined by its electronic structure, whereas the apparent activity can be further optimized by reasonable design on micro-/nanostructures of electrocatalysts. The core goal of electrocatalytic research is to reveal the relationship between the structure and performance of electrocatalysts, which is also the basis of reasonable design and construction of efficient electrocatalysts. Traditional synthetic methods, namely bottom-up and top-down routes, usually induce the change of different structural parameters at the same time. The solid-state conversion strategy, which is converts solid precursors into target materials through chemical reactions, has been widely adopted to produce materials with precisely controllable structures. In this Minireview, we focus on recent advances in the solid-state conversion synthesis of water-splitting electrocatalysts. First, the basis of solid-state conversion chemistry is introduced. Then, the specific methods of precise control of electronic structure by solid-state conversion and the relationship between electronic structure and performance are summarized. Based on the understanding of the electronic structure–performance relationship, synergistic regulation of electronic structure and micro-/nanostructures by solid-state conversion to achieve the copromotion of intrinsic activity and apparent activity are described. Finally, the remaining challenges in this field are discussed, and future research directions are proposed as well.     

Interplay between structure, stoichiometry and properties of technetium nitrides

We report first-principles calculations of the structures and properties of technetium nitride phases within the framework of gradient-corrected density functional theory. Specifically, we have investigated the possible existence of hexagonal Tc(3)N and Tc(2)N subnitrides, following the recent discovery of Re nitrides analogues synthesized directly from the elements. These novel Tc subnitride phases, which are predicted to be stable, are also compared with bulk Tc and Tc mononitride in order to shed light on the intrinsic relationships between the structure, Tc/N stoichiometry, and properties in the Tc-N system.