2D Assembly of Confined Space toward Enhanced CO2 Electroreduction

Rational design of electrocatalysts toward efficient CO₂ electroreduction has the potential to reduce carbon emission and produce value‐added chemicals. In this work, a strategy of constructing 2D confined‐space as molecular reactors for enhanced electrocatalytic CO₂ reduction selectivity is demonstrated. Highly ordered 2D nanosheet lamella assemblies are achieved via weak molecular interaction of atomically thin titania nanosheets, a variety of cationic surfactants, and SnO₂ nanoparticles. The interlayer spacings can be tuned from 0.9 to 3.0 nm by using different surfactant molecules. These 2D assemblies of confined‐space catalysts exhibit a strong size dependence of CO₂ electroreduction selectivity, with a peak Faradaic efficiency of 73% for formate production and excellent electrochemical stability at an optimal interspacing of ≈2.0 nm. This work suggests great potential for constructing new molecular‐size reactors, for highly selective electrocatalytic CO₂ reduction.     

3D Carbon Materials for Efficient Oxygen and Hydrogen Electrocatalysis

Sustainable energy production at an acceptable cost is key for its widespread application. At present, noble metals and metal oxides are the most widely used for electrocatalysis, but they suffer from low selectivity, poor durability, and scarcity. Because of this, metal‐free carbons have become the subject of great interest as promising alternative electrocatalysts for energy conversion and storage devices, and remarkable progress has been accomplished in the advance of metal‐free carbons as electrocatalysts for renewable energy technologies. Particularly interesting are 3D porous carbon architectures, which exhibit outstanding features for electrocatalysis applications, including broad range of active sites, interconnected porosity, high conductivity, and mechanical stability. This review summarizes the latest advances in 3D porous carbon structures for oxygen and hydrogen electrocatalysis. The structure–performance relationship of these materials is consequently rationalized and perspectives on creating more efficient 3D carbon electrocatalysts are suggested.     

Vacancy in Ultrathin 2D Nanomaterials toward Sustainable Energy Application

The unique physicochemical properties of (2D) nanomaterials make them well‐suited for use in sustainable energy applications. Many of these materials can be further improved with vacancy engineering. This review details recent progress in the vacancy engineering of ultrathin 2D nanomaterials. For clarity, it mainly focuses on various ultrathin 2D materials in three categories: X_a&X_aY_b‐, M_aX_b‐, or M_aX_bY_c‐structured materials. Recently developed vacancies in different types of ultrathin 2D materials, as well as their preparation and characterization, are described. Emphasis is placed on the potential electrochemical energy storage and conversion applications of these materials. This review considers the relationship between vacancy properties and material categories of various ultrathin 2D materials in terms of application requirements, preparation, and characterization techniques. The challenges and future outlook of this promising field are summarized.     

Emerging 2D Layered Materials for Perovskite Solar Cells

Perovskite solar cells (PSCs) are now at the forefront of the state‐of‐the‐art photovoltaic technologies due to their high efficiency and low fabrication costs. To further realize the potential of this fascinating class of solar cells, nanostructured functional materials have been playing important roles. 2D layered materials have attracted a great deal of interest due to their fascinating properties and unique structure. Recently, the exploration of a wide range of novel 2D materials for use in PSCs has seen considerable progress, but still a lot remains to be done in this field. In this progress report, the advancements that have recently been made in the application of these emerging 2D materials, beyond graphene, for PSCs are presented. Both the advantages and challenges of these 2D materials for PSCs are highlighted. Finally, important directions for the future advancements toward efficient, low‐cost, and stable PSCs are outlined.     

2-氰基-D,L-苯丙氨酸盐酸盐的合成

合成了非天然氨基酸２－氰基－Ｄ,Ｌ－苯丙氨酸盐以及四个中间体,其结构分别通过红外光谱、核磁共振、元素分析、熔点测试等手段得到确证。     

Enhanced Electrocatalysis for Hydrogen Evolution Reactions from WS2 Nanoribbons

A facile route is developed to boost the electrocatalytic activity of WS₂ by chemically unzipping WS₂ nanotubes to form WS₂ nanoribbons (NRs) with increased edge content. Analysis indicates that the hydrogen evolution reaction activity is strongly associated with the number of exposed active edge sites. The formation of WS₂ NRs is an effective route for controlling the electrochemical properties of the 2D dichalcogenides, enabling their application in electrocatalysis.     

Holey 2D Nanomaterials for Electrochemical Energy Storage

2D nanomaterials provide numerous fascinating properties, such as abundant active surfaces and open ion diffusion channels, which enable fast transport and storage of lithium ions and beyond. However, decreased active surfaces, prolonged ion transport pathway, and sluggish ion transport kinetics caused by self‐restacking of 2D nanomaterials during electrode assembly remain a major challenge to build high‐performance energy storage devices with simultaneously maximized energy and power density as well as long cycle life. To address the above challenge, porosity (or hole) engineering in 2D nanomaterials has become a promising strategy to enable porous 2D nanomaterials with synergetic features combining both 2D nanomaterials and porous architectures. Herein, recent important progress on porous/holey 2D nanomaterials for electrochemical energy storage is reviewed, starting with the introduction of synthetic strategies of porous/holey 2D nanomaterials, followed by critical discussion of design rule and their advantageous features. Thereafter, representative work on porous/holey 2D nanomaterials for electrochemical capacitors, lithium‐ion and sodium‐ion batteries, and other emerging battery technologies (lithium‐sulfur and metal‐air batteries) are presented. The article concludes with perspectives on the future directions for porous/holey 2D nanomaterial in energy storage and conversion applications.     

Emergent Pseudocapacitance of 2D Nanomaterials

Two dimensional (2D) nanomaterials are very attractive due to their unique structural and surface features for energy storage applications. Motivated by the recent pioneering works demonstrating “the emergent pseudocapacitance of 2D nanomaterials,” the energy storage and nanoscience communities could revisit bulk layered materials though state‐of‐the‐art nanotechnology such as nanostructuring, nanoarchitecturing, and compositional control. However, no review has focused on the fundamentals, recent progress, and outlook on this new mechanism of 2D nanomaterials yet. In this study, the key aspects of emergent pseudocapacitors based on 2D nanomaterials are comprehensively reviewed, which covers the history, classification, thermodynamic and kinetic aspects, electrochemical characteristics, and design guidelines of materials for extrinsically surface redox and intercalation pseudocapacitors. The structural and compositional controls of graphene and other carbon nanosheets, transition metal oxides and hydroxides, transition metal dichalcogenides, and metal carbide/nitride on both microscopic and macroscopic levels will be particularly addressed, emphasizing the important results published since 2010. Finally, perspectives on the current impediments and future directions of this field are offered. Unlimited combinations and modifications of 2D nanomaterials can provide a rational strategy to overcome intrinsic limitations of existing materials, offering a new‐generation energy storage materials toward a high and new position in the Ragone plot.     

Identification of Phase Control of Carbon‐Confined Nb2O5 Nanoparticles toward High‐Performance Lithium Storage

Niobium pentoxides (Nb₂O₅) have attracted extensive interest for ultrafast lithium‐ion batteries due to their impressive rate/capacity performance and high safety as intercalation anodes. However, the intrinsic insulating properties and unrevealed mechanisms of complex phases limit their further applications. Here, a facile and efficient method is developed to construct three typical carbon‐confined Nb₂O₅ (TT‐Nb₂O₅@C, T‐Nb₂O₅@C, and H‐Nb₂O₅@C) nanoparticles via a mismatched coordination reaction during the solvothermal process and subsequent controlled heat treatment, and different phase effects are investigated on their lithium storage properties on the basis of both experimental and computational approaches. The thin carbon coating and nanoscale size can endow Nb₂O₅ with a high surface area, high conductivity, and short diffusion length. As a proof‐of‐concept application, when employed as LIB anode materials, the resulting T‐Nb₂O₅@C nanoparticles display higher rate capability and better cycling stability as compared with TT‐Nb₂O₅@C and H‐Nb₂O₅@C nanoparticles. Furthermore, a synergistic effect is investigated and demonstrated between fast diffusion pathways and stable hosts in T‐Nb₂O₅ for ultrafast and stable lithium storage, based on crystal structure analysis, in situ X‐ray diffraction analysis, and density functional theoretical calculations. Therefore, the proposed synthetic strategy and obtained deep insights will stimulate the development of Nb₂O₅ for ultrafast and long‐life LIBs.     

Cell-Free Synthesis of the D2-Cell Adhesion Molecule: Evidence for Three Primary Translation Products

The D2-cell adhesion molecule (D2-CAM) is a membrane glycoprotein that is involved in cell-cell adhesion in the nervous system. To study the biosynthesis of D2-CAM we have translated free and membrane-bound polysomes from rat brain in vitro in the rabbit reticulocyte lysate system. D2-CAM was exclusively synthesized on membrane-bound polysomes. The primary translation products of D2-CAM were three polypeptides of apparent molecular weights 187,000, 134,000, and 112,000. No interconversion between these polypeptides was detected. In contrast to previous suggestions, we conclude that all three D2-CAM polypeptides are primary translation products. When translating polysomes from embryonic and postnatal rat brain, we found that the relative amounts of the three polypeptides synthesized varied with age. Their molecular weights, however, were not age-dependent.     

Antimonene: A Novel 2D Nanomaterial for Supercapacitor Applications

In pursuing higher energy density, without compromising the power density of supercapacitor platforms, the application of an advanced 2D nanomaterial is utilized to maximize performance. Antimonene, for the first time, is characterized as a material for applications in energy storage, being applied as an electrode material as the basis of a supercapacitor. Antimonene is shown to significantly improve the energy storage capabilities of a carbon electrode in both cyclic voltammetry and galvanostatic charging. Antimonene demonstrates remarkable performance with a capacitance of 1578 F g^?1, with a high charging current density of 14 A g^?1. Hence, antimonene is shown to be a highly promising material for energy storage applications. The system also demonstrates a highly competitive energy and power densities of 20 mW h kg^?1 and 4.8 kW kg^?1_, respectively. In addition to the excellent charge storing abilities, antimonene shows good cycling capabilities.     

Graphene Quantum Dots‐Based Advanced Electrode Materials: Design,Synthesis and Their Applications in Electrochemical Energy Storage and Electrocatalysis

Graphene quantum dots (GQDs) have aroused great interest in the scientific community in recent years due to their unique physicochemical properties and potential applications in different fields. To date, much research has been conducted on the ingenious design and rational construction of GQDs‐based nanomaterials used as electrode materials and/or electrocatalysts. Despite these efforts, research on the efficient synthesis and application of GQDs‐based nanomaterials is still in the early stages of development and timely updates of recent research progress on new design concepts, synthetic strategies, and significant breakthroughs in GQDs‐based nanomaterials are highly desired. In light of the above, the effect of synthetic methods on the final product of the GQDs, the GQDs synthesis mechanism, and specific perspectives regarding the effect of the unique surface and structural properties of GQDs (e.g., defects, heteroatom doping, surface/edge state, size, conductivity) on the electrochemical energy‐related systems are discussed in‐depth in this review. Additionally, this review also focuses on the design of GQDs‐based composites and their applications in the fields of electrochemical energy storage (e.g., supercapacitors and batteries) and electrocatalysis (e.g., fuel cell, water splitting, CO₂ reduction), along with constructive suggestions for addressing the remaining challenges in the field.     

Unveiling Pseudo-Inert Basal Plane for Electrocatalysis in 2D Semiconductors: Critical Role of Reversal-Activation Mechanism

Partially occupied orbitals play a pivotal role in enhancing the performance of electrocatalyst by facilitating electron acceptance and donation, thus enabling the activation of molecular bonds. According to this principle, the basal plane of most 2D semiconductors is inert for electrocatalysis because of the fully occupied orbitals at the surface. Here, taking monolayer CrX (X = P, As, Sb) and Cr₂PY (Y = As, Sb) as examples and through first-principles calculations, it is revealed that even with fully occupied surface orbitals, the basal planes exhibit remarkable catalytic activity for the nitrogen oxide reduction reaction (NORR). This leads to the concept of the pseudo-inert electrocatalyst. The underlying physics behind such pseudo-inert character can be attributed to the reversal-activation mechanism: contrary to conventional expectations, the adsorbed NO molecule reversely triggers the activity of the inert basal plane first, and then the basal plane activates NO molecules, forming the intriguing “Reversal Activation-Transfer-Donation-Backdonation” process. This study further predicts that such pseudo-inert character can demonstrate many distinctive properties, for example, it can introduce a novel type of surface catalysis, one that selectively targets radicals possessing an inherent dipole moment such as NO. The explored phenomena and insights greatly enrich the realms of electrocatalysis and 2D materials.     

Mesoporous Decoration of Freestanding Palladium Nanotube Arrays Boosts the Electrocatalysis Capabilities toward Formic Acid and Formate Oxidation

Fabricating high‐performance electrocatalysts is the most critical step in commercializing direct formic acid or formate fuel cells. In this work, a dual‐template electrodeposition method is used to create freestanding mesoporosity decorated palladium nanotube arrays (P‐PdNTA) as a bifunctional electrocatalyst toward formic acid and formate oxidation (FAO/FOR). The phytantriol‐based soft template modifies the superficial chemistry of aluminum anodic oxide inner surfaces, thereby facilitating the regulated electrodeposition of highly stable palladium nanotubes. The sacrifice of the soft template generates substantial mesoporosity on the nanotubes, resulting in a 189% increase in the electrochemically active surface area with respect to the mesopore‐free PdNTA baseline. In addition, the soft template significantly increases the density of catalytically active sites per unit area via perturbation on routine nanotube growth, as evidenced by the doubled areal catalytic activity of P‐PdNTA versus PdNTA. Remarkably, the P‐PdNTA delivered gravimetric catalytic currents of 3.65 and 3.87 A mg^?1 for FAO and FOR, which are 8.5 and 6.5 times higher, respectively, than those of commercial Pt/C. These values are among the most favorable reported and benefit from the unique synergy of fast substance transport, large electrochemical active surface area and high areal population of catalytically active sites.     

2D Materials for Large‐Area Flexible Thermoelectric Devices

The rapid development of the concept of the “Internet of Things (IoT)” requires wearable devices with maintenance‐free batteries, and thermoelectric energy conversion based on large‐area flexible materials has attracted much attention. Among large‐area flexible materials, 2D materials, such as graphene and related materials, are promising for thermoelectric applications due to their excellent transport properties and large power factors. In this Review, both single‐crystalline and polycrystalline 2D materials are surveyed using the experimental reports on thermoelectric devices of graphene, black phosphorus, transition metal dichalcogenides, and other 2D materials. In particular, their carrier‐density dependent thermoelectric properties and power factors maximized by Fermi level tuning techniques are focused. The comparison of the relevant performances between 2D materials and commonly used thermoelectric materials reveals the significantly enhanced power factors in 2D materials. Moreover, the current progress in thermoelectric module applications using large‐area 2D material thin films is summarized, which consequently offers great potential for the use of 2D materials in large‐area flexible thermoelectric device applications. Finally, important remaining issues and future perspectives, such as preparation methods, thermal transports, device designs, and promising effects in 2D materials, are discussed.