in order to restrict the loss of material. Furthermore, due to their scalability and flexibility, 3D flexible electronics (see Supporting Information (SI), where Table S1 contains a list) were considered revolutionary materials and were used in many fields such as imperceptible electronic devices, wearable electronic devices, and bionic technology. [11][12][13] Recently studies have shown the encapsulation of sulfur in the pores of carbon materials, such as meso-/microporous carbons, [11] cable-shaped carbon, [12] and carbon nanotubes/fibers, [13] can reduce the capacity fading. However, such nonpolar flexible carbon materials have a destructive disadvantage; they only have physical van der Waals (vdW) adsorption for polar Li 2 S n , which leads to the facile detachment of Li 2 S n from the carbon surface. [14] This proves that carbon-based materials alone cannot serve as the perfect host. In light of this new insight, various types of polar functional groups on carbon-based materials have been demonstrated to increase the interaction between Li 2 S n species and the electrode; these materials can generally be categorized into three types: polymers (polyaniline, polypyrrole, poly(3,4ethylenedioxythiophene) (PEDOT)), [15] metal oxides

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Lithium‐sulfur (Li‐S) batteries are one of the most promising next‐generation energy‐storage systems. Nevertheless, the sluggish sulfur redox and shuttle effect in Li‐S batteries are the major obstacles to their commercial application. Previous investigations on adsorption for LiPSs have made great progress but cannot restrain the shuttle effect. Catalysts can enhance the reaction kinetics, and then alleviate the shuttle effect. The synergistic relationship between adsorption and catalysis has become the hotspot for research into suppressing the shuttle effect and improving battery performance. Herein, the adsorption‐catalysis synergy in Li‐S batteries is reviewed, the adsorption‐catalysis designs are divided into four categories: adsorption‐catalysis for LiPSs aggregation, polythionate or thiosulfate generation, and sulfur radical formation, as well as other adsorption‐catalysis. Then advanced strategies, future perspectives, and challenges are proposed to aim at long‐life and high‐efficiency Li‐S batteries.

Electrocatalytic water splitting is one of the most promising sustainable energy conversion technologies, but is limited by the sluggish electrochemical reactions. Inorganic nanomaterials have been widely used as efficient catalysts for promoting the electrochemical kinetics. Several approaches to optimize the activities of these nanocatalysts have been developed. The electronic structures of the catalysts play a pivotal role in governing the activity and thus have been identified as an essential descriptor. However, the underlying working mechanisms related to the refined electronic structures remain elusive. To establish the structure–electronic‐behavior–activity relationship, a comprehensive overview of the developed strategies to regulate the electronic structures is presented, emphasizing the surface modification, strain, phase transition, and heterostructure. Current challenges to the fundamental understanding of electron behaviors in the nanocatalysts are fully discussed.

despite all these promises, three intrinsic drawbacks need to be resolved before fulfilling the promise of the market potential.First, the most stable but electronically insulating S 8 (≈10 −14 S cm −2 ) with cyclic configuration is used as the starting material in Li-S cathode, significantly limiting the full utilization of the active materials to reach the theoretical capacity. Therefore, it is the first priority to design the cathode that ensures the maximum usage of the starting materials, which sets the upper limit of the capacity performance. Second, the muti-step reduction process releases highly soluble lithium polysulfides (LiPSs) intermediates (Li 2 S x , where x = 4-8) into the organic electrolyte. [6] Unlike the batteries based on ion-insertion mechanism, [7,8] Li-S battery possesses unique and complex electrochemical/chemical processes during operation. During galvanostatic discharge process, two distinct plateaus can be verified at about 2.4 and 2.1 V in the voltage profile, corresponding to the reduction of sulfur into long-chain polysulfides and subsequent reaction from short-chain polysulfides to Li 2 S, respectively. [9] Further investigations about the reaction mechanism of Li-S battery based on experimental and theoretical studies reveal that the existence of various intermediates during electrochemical processes, indicating much more complex battery chemistry compared to the simple stepwise reaction model. [10,11] As a result, the soluble intermediates can diffuse through the polymeric separator to the anode surface, causing the loss of active materials and degradation of anode. Third, the density difference between the starting material (sulfur, 2.07 g cm −3 ) and discharge product (Li 2 S, 1.66 g cm −3 ) causes significant volumetric change during continuous cycling, damaging the integrity of the cathode structure and leading to serious capacity fading. [12] Besides above problems concerning the cathode side of the Li-S battery, other issues arose on the anode side, such as the unstable solid-electrolyte interphase (SEI), surface passivation, and uncontrolled lithium dendrite growth. [13][14][15] Stemmed from the basic problems mentioned above from the very beginning of the designed Li-S battery systems, various derivative problems were gradually unraveled during persistent efforts for improving the battery performance to approach the ultimate goal for commercialization. In the past decade, fundamental studies about Li-S battery were carried in laboratories all over the world, and it gradually put the puzzle together while brought promising performance improvement. [11,[16][17][18][19][20] However, to date, most of the lab-scale progresses have been based on batteries with sulfur loading lower than 2 mg cm −2 , Lithium-sulfur (Li-S) batteries, due to the high theoretical energy density, are regarded as one of the most promising candidates for breaking the limitations of energy-storage system based on Li-ion batteries. Tremendous efforts have been made to meet the challenge of high-performan...

The oxygen evolution reaction (OER) has been explored extensively for reliable hydrogen supply to boost the energy conversion efficiency. The superior OER performance of newly developed non‐noble metal electrocatalysts has concealed the identification of the real active species of the catalysts. Now, the critical active phase in nickel‐based materials (represented by NiNPS) was directly identified by observing the dynamic surface reconstruction during the harsh OER process via combining in situ Raman tracking and ex situ microscopy and spectroscopy analyses. The irreversible phase transformation from NiNPS to α‐Ni(OH)2 and reversible phase transition between α‐Ni(OH)2 and γ‐NiOOH prior to OER demonstrate γ‐NiOOH as the key active species for OER. The hybrid catalyst exhibits 48‐fold enhanced catalytic current at 300 mV and remarkably reduced Tafel slope to 46 mV dec−1, indicating the greatly accelerated catalytic kinetics after surface evolution.

High-performance electrocatalysts are desired for electrochemical energy conversion, especially in the field of water splitting. Here, a new member of phosphate electrocatalysts, nickel metaphosphate (Ni P O ) nanocrystals, is reported, exhibiting low overpotential of 270 mV to generate the current density of 10 mA cm and a superior catalytic durability of 100 h. It is worth noting that Ni P O electrocatalyst has remarkable oxygen evolution performance operating in basic media. Further experimental and theoretical analyses demonstrate that N dopant boosts the catalytic performance of Ni P O due to optimizing the surface electronic structure for better charge transfer and decreasing the adsorption energy for the oxygenic intermediates.

Due to the predicted excellent electronic properties superior to group VIB (Mo and W) transition metal dichalcogenides (TMDs), group IVB TMDs have enormous potential in nanoelectronics. Here, the synthesis of ultrathin HfS 2 flakes via space-confined chemical vapor deposition, realized by an inner quartz tube, is demonstrated. Moreover, the effect of key growth parameters including the dimensions of confined space and deposition temperature on the growth behavior of products is systematically studied. Typical as-synthesized HfS 2 is a hexagonal-like flake with a smallest thickness of ≈1.2 nm (bilayer) and an edge size of ≈5 µm. The photodetector based on as-synthesized HfS 2 flakes demonstrates excellent optoelectronic performance with a fast photoresponse time (55 ms), which is attributed to the high-quality crystal structure obtained at a high deposition temperature and the ultraclean interface between HfS 2 and the mica substrate. With such properties HfS 2 holds great potential for optoelectronics applications.