Developing noble‐metal‐free electrocatalysts is important to industrially viable ammonia synthesis through the nitrogen reduction reaction (NRR). However, the present transition‐metal ...electrocatalysts still suffer from low activity and Faradaic efficiency due to poor interfacial reaction kinetics. Herein, an interface‐engineered heterojunction, composed of CoS nanosheets anchored on a TiO2 nanofibrous membrane, is developed. The TiO2 nanofibrous membrane can uniformly confine the CoS nanosheets against agglomeration, and contribute substantially to the NRR performance. The intimate coupling between CoS and TiO2 enables easy charge transfer, resulting in fast reaction kinetics at the heterointerface. The conductivity and structural integrity of the heterojunction are further enhanced by carbon nanoplating. The resulting C@CoS@TiO2 electrocatalyst achieves a high ammonia yield (8.09×10−10 mol s−1 cm−2) and Faradaic efficiency (28.6 %), as well as long‐term durability.
Junction box: An interface‐engineered heterojunction, composed of carbon‐nanoplated CoS@TiO2 nanofibrous membrane, is developed for the nitrogen reduction reaction. The resulting C@CoS@electrocatalyst achieves strikingly high ammonia yield (8.09×10−10 mol s−1 cm−2) and Faradaic efficiency (28.6 %), as well as long‐term durability.
A conceptually new, metal‐free electrocatalyst, black phosphorus (BP) is presented, which is further downsized to quantum dots (QDs) for larger surface areas, and thus, more active sites than the ...bulk form. However, BP QDs are prone to agglomeration, which inevitably results in the loss of active sites. Besides, their poor conductivity is not favorable for charge transport during electrolysis. To solve these problems, an electrochemically active, electrically conductive matrix, black tin oxide (SnO2−x) nanotubes, is employed for the first time. Through facile self‐assembly, BP QDs are stably confined on the SnO2−x nanotubes due to Sn‐P coordination, resulting in a robust, double‐active electrocatalyst. Benefiting from their synergistic superiority, the BP@SnO2−x nanotubes deliver impressively high ammonia yield and Faradaic efficiency, which represent a successful attempt toward advanced hybrid electrocatalysts for ambient nitrogen fixation.
Through facile self‐assembly, black phosphorus quantum dots are stably confined on SnO2−x nanotubes, which serve as an electrocatalytically active and electrically conductive matrix. Benefiting from their synergistic superiority, the two components result in a robust, double‐active electrocatalyst delivering impressively high ammonia yield and Faradaic efficiency.
Recently, a new class of 2D materials, i.e., transition metal carbides, nitrides, and carbonitrides known as MXenes, is unveiled with more than 20 types reported one after another. Since they are ...flexible and conductive, MXenes are expected to compete with graphene and other 2D materials in many applications. Here, a general route is reported to simple self‐assembly of transition metal oxide (TMO) nanostructures, including TiO2 nanorods and SnO2 nanowires, on MXene (Ti3C2) nanosheets through van der Waals interactions. The MXene nanosheets, acting as the underlying substrate, not only enable reversible electron and ion transport at the interface but also prevent the TMO nanostructures from aggregation during lithiation/delithiation. The TMO nanostructures, in turn, serve as the spacer to prevent the MXene nanosheets from restacking, thus preserving the active areas from being lost. More importantly, they can contribute extraordinary electrochemical properties, offering short lithium diffusion pathways and additional active sites. The resulting TiO2/MXene and SnO2/MXene heterostructures exhibit superior high‐rate performance, making them promising high‐power and high‐energy anode materials for lithium‐ion batteries.
Transition metal oxide (TMO) nanostructures are self‐assembled on MXene nanosheets in tetrahydrofuran through van der Waals interactions, resulting in novel TMO/MXene heterostructures. Due to remarkable morphological and functional synergy, the TMO/MXene heterostructures exhibit superior high‐rate performance, which rank them as promising anode materials for fast and stable lithium storage.
The key to bringing the electrocatalytic nitrogen fixation from conception to application lies in the development of high‐efficiency, cost‐effective electrocatalysts. Layered double hydroxides ...(LDHs), also known as hydrotalcites, are promising electrocatalysts for water splitting due to multiple metal centers and large surface areas. However, their activities in the electrocatalytic nitrogen fixation are unsatisfactory. Now, a simple and effective way of phosphorus doping is presented to regulate the charge distribution in LDHs, thus promoting the nitrogen adsorption and activation. The P‐doped LDHs are further coupled to a self‐supported, conductive matrix, that is, a carbon nanofibrous membrane, which prevents their aggregation as well as ensuring rapid charge transfer at the interface. By this strategy, decent ammonia yield (1.72×10−10 mol s−1 cm−2) and Faradaic efficiency (23 %) are delivered at −0.5 V vs. RHE in 0.1 m Na2SO4.
Through phosphorus doping, the charge distribution in Fe‐Ni layered double hydroxide (LDH) is regulated to promote the activation of nitrogen. This strategy offers an opportunity of tapping the unknown potentials of the well‐known hydrotalcites (LDHs) in the field of electrocatalytic nitrogen fixation.
Ceramic aerogels are attractive for many applications due to their ultralow density, high porosity, and multifunctionality but are limited by the typical trade-off relationship between mechanical ...properties and thermal stability when used in extreme environments. In this work, we design and synthesize ceramic nanofibrous aerogels with three-dimensional (3D) interwoven crimped-nanofibre structures that endow the aerogels with superior mechanical performances and high thermal stability. These ceramic aerogels are synthesized by a direct and facile route, 3D reaction electrospinning. They display robust structural stability with structure-derived mechanical ultra-stretchability up to 100% tensile strain and superior restoring capacity up to 40% tensile strain, 95% bending strain and 60% compressive strain, high thermal stability from -196 to 1400 °C, repeatable stretchability at working temperatures up to 1300 °C, and a low thermal conductivity of 0.0228 W m
K
in air. This work would enable the innovative design of high-performance ceramic aerogels for various applications.
Recently, various titanium dioxide (TiO2) nanostructures have received increasing attention in the fields of energy conversion and storage owing to their electrochemical properties. However, these ...particulate nanomaterials exclusively exist in the powder form, which may cause health risks and environmental hazards. Herein we report a novel, highly elastic bulk form of TiO2 for safe use and easy recycling. Specifically, TiO2 nanofibrous aerogels (NAs) consisting of resiliently bonded, flexible TiO2 nanofibers are constructed, which have an ultralow bulk density, ultrahigh porosity, and excellent elasticity. To promote charge transfer, they are subjected to lithium reduction to generate abundant oxygen vacancies, which can modulate the electronic structure of TiO2, resulting in a conductivity up to 38.2 mS cm−1. As a proof‐of‐concept demonstration, the conductive and elastic TiO2 NAs serve as a new type of self‐supported electrocatalyst for ambient nitrogen fixation, achieving an ammonia yield of 4.19×10−10 mol s−1 cm−2 and a Faradaic efficiency of 20.3 %. The origin of the electrocatalytic activity is revealed by DFT calculations.
Conductive and elastic TiO2 nanofibrous aerogels (NAs), with a hierarchically ordered, cellular architecture consisting of resiliently bonded nanofibers, can be prepared. As a proof‐of‐concept demonstration, the TiO2 NAs serve as a new type of self‐supported electrocatalysts with high activity and durability for ambient nitrogen fixation.
Electrochemical nitrogen reduction reaction (eNRR) is promising in place of the Haber–Bosch process for artificial N2 fixation. However, the high activity and selectivity of eNRR are challenging to ...achieve simultaneously due to the scaling relations. Such “leverage” between activity and selectivity has severely restricted eNRR. To overcome this bottleneck, the complementary design of electronic structures in multicomponent electrocatalysts has been recently pursued, aiming to maximize the advantages of each component and optimize the multistep reactions, which has stood at the cutting edge in this aspect. Here, we present a minireview of the design, performance, and mechanism of multicomponent electrocatalysts with complementary electronic structures. We particularly emphasize the interactions between N2 and elements from d‐, p‐, and s‐blocks, which are essential for understanding how these electrocatalysts are beyond the “leverage” between activity and selectivity.
By integrating distinct yet complementary electronic structures of elements in different blocks, this concept is revolutionary in that it breaks the limitations of scaling relations, synchronously achieving high activity and selectivity for electrochemical nitrogen reduction.
Being conductive and flexible, MXenes, including transition metal carbides and nitrides, are expected to compete with, or even outperform graphene as 2D substrates serving in versatile applications. ...On the other hand, the extraordinary electrochemical activities of MXenes make them promising candidates as electrode materials in rechargeable batteries and supercapacitors, or as electrocatalysts in water splitting. However, MXenes are inclined to self‐restack due to hydrogen bonding or van der Waals interactions, which may lead to substantial loss of electroactive area as well as inaccessibility of ions and electrolytes. In this sense, hybridizing 2D MXenes and low‐dimensional inorganic nanostructures in elaborately designed architectures is of utmost significance, and provides a chance to integrate their unique properties in a complementary way. As such, this review is dedicated to highlighting recent progress in this regime, putting emphasis on the methods, structural and functional synergies, and energy‐related applications. Moreover, the present challenges and the future development directions are also discussed in depth.
Hybridizing 2D MXenes and low‐dimensional inorganic nanostructures in elaborately designed architectures is of utmost significance, and provides a chance to integrate their unique properties in a complementary way. This review highlights recent progress in this regime, putting emphasis on the methods, structural and functional synergies, and energy‐related applications. Moreover, the present challenges and the future development directions are also discussed.
Traditional oxide ceramics are inherently brittle and highly sensitive to defects, making them vulnerable to failure under external stress. As such, endowing these materials with high strength and ...high toughness simultaneously is crucial to improve their performance in most safety‐critical applications. Fibrillation of the ceramic materials and further refinement of the fiber diameter, as realized by electrospinning, are expected to achieve the transformation from brittleness to flexibility owing to the structural uniqueness. Currently, the synthesis of electrospun oxide ceramic nanofibers must rely on an organic polymer template to regulate the spinnability of the inorganic sol, whose thermal decomposition during ceramization will inevitably lead to pore defects, and seriously weaken the mechanical properties of the final nanofibers. Here, a self‐templated electrospinning strategy is proposed for the formation of oxide ceramic nanofibers without adding any organic polymer template. An example is given to show that individual silica nanofibers have an ideally homogeneous, dense, and defect‐free structure, with tensile strength as high as 1.41 GPa and toughness up to 34.29 MJ m−3, both of which are far superior to the counterparts prepared by polymer‐templated electrospinning. This work provides a new strategy to develop oxide ceramic materials that are strong and tough.
A self‐templated electrospinning strategy is proposed for the formation of oxide ceramic nanofibers, which exhibit high strength and high toughness simultaneously owing to their ideally homogeneous, dense, and defect‐free structure.
Carbon aerogels (CAs) are desirable for thermal protection in aerospace because of their lightweight and high‐temperature insulation characteristic; however, their intrinsic brittleness and flaw ...sensitivity easily trigger catastrophic failure when resisting high‐frequency thermal shocks or complex mechanical stresses. Compression is the predominant load applied on aerogels by aerodynamic pressure and pre‐tightening force; therefore, the structural elasticity and exceptional capability to keep thermal performance under impact stress are crucial in deciding the actual availability of aerogels. This review presents the recent progress in newly resilient CAs for thermal protection, focusing on reliable structural stability, thermal stability, and thermal superinsulation property. The influence law of microstructures on heat transfer behaviors is first investigated, followed by construction strategies for adiabatic CAs, emphasizing the recoverable deformability resulting from increased continuity of building blocks from 0D nanoparticles to 1D nanofibers/nanotubes and then to 2D nanosheets. Moreover, the optimization of thermal stability in high‐temperature aerobic environments and thermal insulation performance are discussed. Finally, it raises current challenges and further opportunities for CAs toward better properties and brighter prospects.
Superelastic and superinsulation carbon aerogels are highly promising for thermal protection under extreme conditions. This review presents a comprehensive insight into recent advances in this emerging material, focusing on fundamental heat transfer mechanisms, nanostructured engineering strategies, optimization pathways for thermal stability and thermal insulation performance, as well as current challenges and future developments.
