Aconceptually new,metal-free electrocatalyst, black phosphorus (BP) is presented, which is further downsized to quantum dots (QDs) for larger surface areas,a nd thus,m ore active sites than the bulk form. However,BPQDs are prone to agglomeration, which inevitably results in the loss of active sites.B esides,t heir poor conductivity is not favorable for charge transport during electrolysis.T os olve these problems, an electrochemically active,e lectrically conductive matrix, black tin oxide (SnO 2Àx )n anotubes,i se mployed for the first time.T hrough facile self-assembly,B PQ Ds are stably confined on the SnO 2Àx nanotubes due to Sn-P coordination, resulting in ar obust, double-active electrocatalyst. Benefiting from their synergistic superiority,t he BP@SnO 2Àx nanotubes deliver impressively high ammonia yield and Faradaic efficiency,w hich represent as uccessful attempt towarda dvanced hybrid electrocatalysts for ambient nitrogen fixation.

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.

Developing noble-metal-free electrocatalysts is important to industrially viable ammonia synthesis through the nitrogen reduction reaction (NRR). However,t he present transition-metal electrocatalysts still suffer from low activity and Faradaic efficiency due to poor interfacial reaction kinetics.H erein, an interface-engineered heterojunction, composed of CoS nanosheets anchored on aT iO 2 nanofibrous membrane,isdeveloped. The TiO 2 nanofibrous membrane can uniformly confine the CoS nanosheets against agglomeration, and contribute substantially to the NRR performance.T he intimate coupling between CoS and TiO 2 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.T he resulting C@CoS@TiO 2 electrocatalyst achieves ah igh ammonia yield (8.09 10 À10 mol s À1 cm À2 )and Faradaic efficiency (28.6 %), as well as long-term durability.The electrocatalytic nitrogen reduction reaction (NRR) is ap romising alternative to the energy-consuming Haber-Bosch process toward ammonia synthesis since it can be operated under ambient conditions. [1] To enable efficient nitrogen fixation, highly active electrocatalysts are required, which are mostly noble metals such as Au, [2][3][4] Pt, [5] and Ru. [6,7] Recently,t he research focus turned to the development of low-cost electrocatalysts composed of earth-abundant elements,s uch as transition metals,s ince their unoccupied dorbitals were able to accept the electrons of nitrogen, and thus,break the highly symmetric electronic cloud of the NN bonds.A ss uch, various nanostructures of transition metal oxides, [8][9][10][11][12] sulfides, [13] nitrides, [14,15] and carbides, [16][17][18] were explored as possible NRR electrocatalysts.H owever,n anostructured transition-metal compounds suffer from low activity and Faradaic efficiency resulting from two inherent deficiencies,t hat is,s trong agglomeration tendencya nd poor conductivity.T herefore,s everal studies employed car-Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

speed airflow scouring. Accordingly, the thermal protection system (TPS) must be applied on their surface to cope with the integrated heat load accumulated during flight. [2] The lightweight nature of TPS is critical in addressing the criteria for ultralong-range combat military weapons with high sound speeds and load capacities while considering the production cost in check. Kistler of Stanford University first proposed the concept of aerogel in 1931, [3] which was fabricated by exchanging the liquid in a wet gel by gas whilst guaranteeing that the internal structure did not collapse, becoming one of the lightest solid materials known to date. The abundance of internal nanoscale pore size and highly tortuous pore structure determine aerogel's excellent thermally insulation performance, with the thermal conductivity as low as 0.005 W m −1 K −1 . [4] NASA pioneered the use of aerogels as efficient insulating materials on several Mars rovers and spacecraft parts, such as the insulation assembly of Rover Mars batteries, the outer surface of vehicle decelerators, [5] etc., and is also advancing their application in extra-vehicular insulating suits. [6] Oxide ceramic aerogels have currently been the most rapidly developed in high-temperature insulation; however, due to the restrictions of crystallization-induced pulverization, large thermal expansion, and relatively low operating temperatures, for example, SiO 2 (650 °C), [7] ZrO 2 (1100 °C), [8] Al 2 O 3 (1300 °C), [9] and mullite (1400 °C), these aerogels and their composites suffer from severe strength deterioration and catastrophic structural failure during significant temperature gradient changes or long-term high-temperature exposure. [10] Conversely, carbon aerogels (CAs) maintain their mesoporous structure despite heat treatment over 2500 °C under a vacuum or inert atmosphere, showing favorable thermal stability at ultra-high temperatures. [11] In addition, they also have a much higher specific extinction coefficient (190 m 2 kg −1 ) than others (e.g., SiO 2 aerogel with 20 m 2 kg −1 ), which leads to lower radiative thermal conductivities. [12] Therefore, CAs are anticipated to be up-and-coming candidates for the TPS of hypersonic vehicles in conditions of severe heat flow density and ultra-high temperatures.The terms of CAs initially referred to carbonaceous substances that exist as 3D monoliths macroscopically and

Recently,v arious titanium dioxide (TiO 2)n anostructures have received increasing attention in the fields of energy conversion and storage owingt ot heir electrochemical properties.H owever,t hese particulate nanomaterials exclusively exist in the powder form, which may cause health risks and environmental hazards.H erein we report an ovel, highly elastic bulk form of TiO 2 for safe use and easy recycling. Specifically,T iO 2 nanofibrous aerogels (NAs) consisting of resiliently bonded, flexible TiO 2 nanofibers are constructed, which have an ultralowb ulk density,u ltrahigh porosity,a nd excellent elasticity.T op romote charge transfer,t hey are subjected to lithium reduction to generate abundant oxygen vacancies,whichcan modulate the electronic structure of TiO 2 , resulting in ac onductivity up to 38.2 mS cm À1 .A saproof-ofconcept demonstration, the conductive and elastic TiO 2 NAs serve as an ew type of self-supported electrocatalyst for ambient nitrogen fixation, achieving an ammonia yield of 4.19 10 À10 mol s À1 cm À2 and aF aradaic efficiency of 20.3 %. The origin of the electrocatalytic activity is revealed by DFT calculations.