Attractive hydrogen production? The amorphous Fe nanoparticles prepared following a simple but very efficient method possess high catalytic activity (see picture) for the generation of hydrogen from ...an aqueous solution of ammonia borane, even in air, and can readily be recycled with no obvious loss of catalytic activity.
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The pressing demand on the electronic vehicles with long driving range on a single charge has necessitated the development of next‐generation high‐energy‐density batteries. Non‐aqueous Li‐O2 ...batteries have received rapidly growing attention due to their higher theoretical energy densities compared to those of state‐of‐the‐art Li‐ion batteries.To make them practical for commercial applications, many critical issues must be overcome, including low round‐trip efficiency and poor cycling stability, which are intimately connected to the problems resulting from cathode degradation during cycling. Encouragingly, during the past years, much effort has been devoted to enhancing the stability of the cathode using a variety of strategies and these have effectively surmounted the challenges derived from cathode deteriorations,thus endowing Li‐O2 batteries with significantly improved electrochemical performances. Here, a brief overview of the general development of Li‐O2 battery is presented. Then, critical issues relevant to the cathode instability are discussed and remarkable achievements in enhancing the cathode stability are highlighted. Finally, perspectives towards the development of next generation highly stable cathode are also discussed.
Recent research on enhancing the mechanical and chemical stability of cathodes for non‐aqueous Li‐O2 batteries is summarized. In light of recent achievements, the structural integrity of the constructed cathode can be well‐maintained with a rational architectural design and the chemical stability can be effectively improved with the construction of a protective layer on the cathode.
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A dimethyl sulfoxide (DMSO) based electrolyte is first proposed for rechargeable lithium-O(2) (Li-O(2)) batteries. Superior battery performances, including high discharge capacity and low charge ...potential, are successfully obtained.
Rechargeable sodium–oxygen (Na–O2) batteries are of interest due to their high specific capacity, high equilibrium potential output, and the abundance of sodium resources; however, their cycle life ...is still very poor due to instability of electrolytes and especially the uncontrollable growth of Na dendrites. Herein, as a proof‐of‐concept experiment, a facile and low‐cost strategy is first proposed and demonstrated to effectively suppress growth of Na dendrites by using a fibrillar polyvinylidene fluoride film (f‐PVDF) with nonthrough pore as a multifunctional blocking interlayer. Unexpectedly, the f‐PVDF interlayer endows Na–O2 battery with superior electrochemical performances, including high rate capability and long cycle life (up to 87 cycles), which is superior to those of the compact PVDF (c‐PVDF), PVDF with through pores (p‐PVDF), polyethylene oxide (PEO), and conventional polytetrafluoroethylene (PTFE) counterparts due to the following combined advantages: (1) the stronger CF polar function groups provide a better affinity to Na ions, thus enabling a more homogeneous Na deposition than that of CO function groups in PEO interlayer; (2) compared with c‐PVDF and p‐PVDF interlayers, f‐PVDF holds more electrolyte uptake for higher ion conductivity; (3) the good wettability of the f‐PVDF interlayer with electrolyte benefits Na dendrite suppression compared with PTFE interlayer.
Stable and fibrillar polyvinylidene fluoride films (f‐PVDFs) with strongly polar functional groups are prepared as the blocking interlayer for Na dendrites suppression. Surprisingly, the films efficiently suppress dendrite formation and greatly improve the cycle life of Na–O2 batteries, which is attributed to f‐PVDF's high electrolyte uptake, good adhesion to Na ionic flux, and excellent affinity to the electrolyte.
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To promote the development of high energy Li–O2 batteries, it is important to design and construct a suitable and effective oxygen‐breathing cathode. Herein, activated cobalt‐nitrogen‐doped carbon ...nanotube/carbon nanofiber composites (Co‐N‐CNT/CNF) as the effective cathodes for Li–O2 batteries are prepared by in situ chemical vapor deposition (CVD). The unique architecture of these electrodes facilitates the rapid oxygen diffusion and electrolyte penetration. Meanwhile, the nitrogen‐doped carbon nanotube/carbon nanofiber (N‐CNT/CNF) and Co/CoNx serve as reaction sites to promote the formation/decomposition of discharge product. Li–O2 batteries with Co‐N‐CNT/CNF cathodes exhibit superior electrochemical performance in terms of a positive discharge plateau (2.81 V) and a low charge overpotential (0.61 V). Besides, Li–O2 batteries also present a high discharge capacity (11512.4 mAh g−1 at 100 mA g−1), and a long cycle life (130 cycles). Meanwhile, the Co‐N‐CNT/CNF cathode also has an excellent flexibility, thus the assembled flexible battery with Co‐N‐CNT/CNF can work normally and hold a wonderful capacity rate under various bending conditions.
Activated cobalt‐nitrogen‐doped carbon nanotube/carbon nanofiber composites (Co‐N‐CNT/CNF) cathodes are prepared via in situ chemical vapor deposition. The Li–O2 batteries with these cathodes exhibit great performances. Meanwhile, Co‐N‐CNT/CNF cathodes are flexible, based on which the assembled flexible battery exhibits great performances and flexibility under various bending conditions.
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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.
Another dimension! An integrated 3D bismuth oxide ultrathin nanosheets/carbon foam electrode with a unique array foam architecture for highly efficient mass transfer and optimized exposed active sites has been designed by a sponge effect and N‐atom anchor for energy‐efficient, long‐term durable, and selective electrocatalytic conversion of CO2 to HCOOH (see figure).
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The severe performance degradation of high‐capacity Li−O2 batteries induced by Li dendrite growth and concentration polarization from the low Li+ transfer number of conventional electrolytes hinder ...their practical applications. Herein, lithiated Nafion (LN) with the sulfonic group immobilized on the perfluorinated backbone has been designed as a soluble lithium salt for preparing a less flammable polyelectrolyte solution, which not only simultaneously achieves a high Li+ transfer number (0.84) and conductivity (2.5 mS cm−1), but also the perfluorinated anion of LN produces a LiF‐rich SEI for protecting the Li anode from dendrite growth. Thus, the Li−O2 battery with a LN‐based electrolyte achieves an all‐round performance improvement, like low charge overpotential (0.18 V), large discharge capacity (9508 mAh g−1), and excellent cycling performance (225 cycles). Besides, the fabricated pouch‐type Li–air cells exhibit promising applications to power electronic equipment with satisfactory safety.
A novel design principle of polymerization and fluorination for salt anions has been proposed and lithiated Nafion (LN) was suggested as a representative soluble lithium salt for the polyelectrolyte solution to improve the Li+ transfer number and produce a LiF‐rich solid electrolyte interface (SEI). Furthermore, the perfluorinated backbone of LN delivers the polyelectrolyte solution low flammability. Thus, making the Li−O2 batteries realize all‐round performance amelioration.
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The performance of electrode material is correlated with the choice of electrolyte, however, how the solvation has significant impact on electrochemical behavior is underdeveloped. Herein, ...N‐heteropentacenequinone (TAPQ) is investigated to reveal the solvation effect on the performance of sodium‐ion batteries in different electrolyte environment. TAPQ cycled in diglyme‐based electrolyte exhibits superior electrochemical performance, but experiences a rapid capacity fading in carbonate‐based electrolyte. The function of solvation effect is mainly embodied in two aspects: one is the stabilization of anion intermediate via the compatibility of electrode and electrolyte, the other is the interfacial electrochemical characteristics influenced by solvation sheath structure. By revealing the failure mechanism, this work presents an avenue for better understanding electrochemical behavior and enhancing performance from the angle of solvation effect.
N‐heteropentacenequinone (TAPQ) is studied as electrode material to investigate the solvation effect in different sodium‐ion battery electrolytes. By revealing the failure mechanism of TAPQ in carbonate‐based electrolytes, we discuss how the solvation effect influences interfacial electrochemical characteristics and attributed the electrolyte compatibility to the stabilization effect of reaction intermediate via solvation effect.
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There is a demand for a sufficient and sustainable energy supply. Hence, the search for applicable hydrogen storage materials is extremely important owing to the diversified merits of hydrogen ...energy. Lithium and sodium borohydride, ammonia borane, hydrazine, and formic acid have been extensively investigated as promising hydrogen storage materials based on their relatively high hydrogen content. Significant advances, such as hydrogen generation temperatures and reaction kinetics, have been made in the catalytic hydrolysis of aqueous lithium and sodium borohydride and ammonia borane as well as in the catalytic decomposition of hydrous hydrazine and formic acid. In this Minireview we briefly survey the research progresses in catalytic hydrogen generation from these liquid‐phase chemical hydrogen storage materials.
The search for applicable hydrogen storage materials is extremely important owing to the diversified merits of hydrogen energy. Lithium and sodium borohydride (aq.), ammonia borane (aq.), hydrous hydrazine, and formic acid have been extensively investigated as promising hydrogen storage materials based on their relatively high hydrogen content. In this Minireview we briefly survey the research progresses in catalytic hydrogen generation from these liquid‐phase chemical hydrogen storage materials.
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Organic materials have attracted much attention in aqueous zinc‐ion batteries (AZIBs) due to their sustainability and structure‐designable, but their further development is hindered by the high ...solubility, poor conductivity, and low utilization of active groups, resulting in poor cycling stability, terrible rate capability, and low capacity. In order to solve these three major obstacles, a novel organic host, benzobnaphtho2’,3’:5,61,4dithiino2,3‐ithianthrene‐5,7,9,14,16,18‐hexone (BNDTH), with abundant electroactive groups and stable extended π‐conjugated structure is synthesized and composited with reduced graphene oxide (RGO) through a solvent exchange composition method to act as the cathode material for AZIBs. The well‐designed BNDTH/RGO composite exhibits a high capacity of 296 mAh g−1 (nearly a full utilization of the active groups), superior rate capability of 120 mAh g−1, and a long lifetime of 58 000 cycles with a capacity retention of 65% at 10 A g−1. Such excellent performance can be attributed to the ingenious structural design of the active molecule, as well as the unique solvent exchange composition strategy that enables effective dispersion of excess charge on the active molecule during discharge/charge process. This work provides important insights for the rational design of organic cathode materials and has significant guidance for realizing ideal high performance in AZIBs.
A fully composited benzobnaphtho2',3':5,61,4dithiino2,3‐ithianthrene‐5,7,9,14,16,18‐hexone/reduced graphene oxide (BNDTH/RGO) is designed to simultaneously conquer the low utilization of active sites, intrinsic poor conductivity, and strong solubility of organic electrode materials, realizing the construction of Zn‐organic batteries with record‐high cycling stability. This work brings new opportunities for the exploration of ultra‐stable organic cathode materials for Zn‐ion batteries.
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