Atomically dispersed dinuclear iridium active sites for efficient and stable electrocatalytic chlorine evolution reaction.

The electrochemical chlorine evolution reaction (CER) is a critical anode reaction in chlor-alkali electrolysis. Although precious metal-based mixed metal oxides (MMOs) have long been used as CER catalysts, they suffer from high cost and poor selectivity due to the competing oxygen evolution reaction (OER). Single-atom catalysts (SACs), featuring high atom utilization efficiency, have captured widespread interest in diverse applications. However, the single-atom sites in SACs are generally recognized as independent motifs and the interplay of adjacent sites is largely overlooked. Herein, we report a "precursor-preselected" cage-encapsulated strategy to synthesize atomically dispersed dinuclear iridium active sites bridged by oxygen that are supported on nitrogen-doped carbon (Ir2-ONC). The dinuclear Ir2-ONC catalyst exhibits a CER onset potential of 1.375 V vs. normal hydrogen electrode, a high faradaic efficiency of >95%, and a high mass activity of 14321.6 A gIr -1, much better than the Ir SACs, which demonstrates the significance of coordination and electronic structure regulation for atomically dispersed catalysts. Density functional theory calculations and ab initio molecular dynamics simulations confirm that the unique dinuclear structure facilitates Cl- adsorption, resulting in improved catalytic CER performance.

Novel Quasi-Liquid K-Na Alloy as a Promising Dendrite-Free Anode for Rechargeable Potassium Metal Batteries.

Rechargeable potassium metal batteries are promising energy storage devices with potentially high energy density and markedly low cost. However, eliminating dendrite growth and achieving a stable electrode/electrolyte interface are the key challenges to tackle. Herein, a novel "quasi-liquid" potassium-sodium alloy (KNA) anode comprising only 3.5 wt% sodium (KNA-3.5) is reported, which exhibits outstanding electrochemical performance able to be reversibly cycled at 4 mA cm-2 for 2000 h. Moreover, it is demonstrated that adding a small amount of sodium hexafluorophosphate (NaPF6 ) into the potassium bis(fluorosulfonyl)imide electrolyte allows for the formation of the "quasi-liquid" KNA on electrode surface. Comprehensive experimental studies reveal the formation of an unusual metastable KNa2 phase during plating, which is believed to facilitate simultaneous nucleation and suppress the growth of dendrites, thereby improving the electrode's cycle lifetime. The "quasi-liquid" KNA-3.5 anode demonstrates markedly enhanced electrochemical performance in a full cell when pairing with Prussian blue analogs or sodium rhodizonate dibasic as the cathode material, compared to the pristine potassium anode. Importantly, unlike the liquid KNA reported before, the "quasi-liquid" KNA-3.5 exhibits good processability and can be readily shaped into sheet electrodes, showing substantial promise as a dendrite-free anode in rechargeable potassium metal batteries.

NiFe2O4 nanoparticles coated on 3D graphene capsule as electrode for advanced energy storage applications.

Current energy crises are inspiring researchers to focus intensively on development of feasible ways to produce high performing composite electrode materials for increasing energy demands. The present work addresses this objective by developing a novel structure of NiFe2O4 (NFO) nanoparticles coated on graphene capsules (GCs) by a simple hydrothermal technique. This NFO-GCs electrode material was subjected to different types of electrochemical performance evaluations to investigate its feasibility as a supercapacitor electrode. The as-prepared NFO-GCs nanocomposite electrode exhibits high specific capacitance of 1028 F g-1 at a current density of 2 A g-1 and 94% capacitance retention at the end of 10 000 charge-discharge cycles, whereas pristine NFO electrode shows 720 F g-1 specific capacitance with 88% capacitance retention. The high specific capacitance, good rate capability, and excellent cycling stability of NFO-GCs composite can be attributed to effective synergism between the GCs and NFO. The superior electrochemical performance of NFO-GCs nanocomposite demonstrates possible application of this material as a working electrode for fully functional supercapacitor devices.

Boosting potassium-ion batteries by few-layered composite anodes prepared via solution-triggered one-step shear exfoliation.

Earth-abundant potassium is a promising alternative to lithium in rechargeable batteries, but a pivotal limitation of potassium-ion batteries is their relatively low capacity and poor cycling stability. Here, a high-performance potassium-ion battery is achieved by employing few-layered antimony sulfide/carbon sheet composite anode fabricated via one-step high-shear exfoliation in ethanol/water solvent. Antimony sulfide with few-layered structure minimizes the volume expansion during potassiation and shortens the ion transport pathways, thus enhancing the rate capability; while carbon sheets in the composite provide electrical conductivity and maintain the electrode cycling stability by trapping the inevitable by-product, elemental sulfur. Meanwhile, the effect of the exfoliation solvent on the fabrication of two-dimensional antimony sulfide/carbon is also investigated. It is found that water facilitates the exfoliation by lower diffusion barrier along the [010] direction of antimony sulfide, while ethanol in the solvent acts as the carbon source for in situ carbonization.

Few Atomic Layered Lithium Cathode Materials to Achieve Ultrahigh Rate Capability in Lithium-Ion Batteries.

The most promising cathode materials, including LiCoO2 (layered), LiMn2 O4 (spinel), and LiFePO4 (olivine), have been the focus of intense research to develop rechargeable lithium-ion batteries (LIBs) for portable electronic devices. Sluggish lithium diffusion, however, and unsatisfactory long-term cycling performance still limit the development of present LIBs for several applications, such as plug-in/hybrid electric vehicles. Motivated by the success of graphene and novel 2D materials with unique physical and chemical properties, herein, a simple shear-assisted mechanical exfoliation method to synthesize few-layered nanosheets of LiCoO2 , LiMn2 O4 , and LiFePO4 is used. Importantly, these as-prepared nanosheets with preferred orientations and optimized stable structures exhibit excellent C-rate capability and long-term cycling performance with much reduced volume expansion during cycling. In particular, the zero-strain insertion phenomenon could be achieved in 2-3 such layers of LiCoO2 electrode materials, which could open up a new way to the further development of next-generation long-life and high-rate batteries.

An All-Integrated Anode via Interlinked Chemical Bonding between Double-Shelled-Yolk-Structured Silicon and Binder for Lithium-Ion Batteries.

The concept of an all-integrated design with multifunctionalization is widely employed in optoelectronic devices, sensors, resonator systems, and microfluidic devices, resulting in benefits for many ongoing research projects. Here, maintaining structural/electrode stability against large volume change by means of an all-integrated design is realized for silicon anodes. An all-integrated silicon anode is achieved via multicomponent interlinking among carbon@void@silica@silicon (CVSS) nanospheres and cross-linked carboxymethyl cellulose and citric acid polymer binder (c-CMC-CA). Due to the additional protection from the silica layer, CVSS is superior to the carbon@void@silicon (CVS) electrode in terms of long-term cyclability. The as-prepared all-integrated CVSS electrode exhibits high mechanical strength, which can be ascribed to the high adhesivity and ductility of c-CMC-CA binder and the strong binding energy between CVSS and c-CMC-CA, as calculated based on density functional theory (DFT). This electrode exhibits a high reversible capacity of 1640 mA h g-1 after 100 cycles at a current density of 1 A g-1 , high rate performance, and long-term cycling stability with 84.6% capacity retention after 1000 cycles at 5 A g-1 .

Smart design of free-standing ultrathin Co-Co(OH)2 composite nanoflakes on 3D nickel foam for high-performance electrochemical capacitors.

Ultrathin Co-Co(OH)2 composite nanoflakes have been fabricated through electrodeposition on 3D nickel foam. As electrochemical capacitor electrodes, they exhibit a high specific capacitance of 1000 F g(-1) at the scan rate of 5 mV s(-1) and 980 F g(-1) at the current density of 1 A g(-1), respectively, and the retention of capacitance is 91% after 5000 cycles.

Facile synthesis of Ag/GNS-g-PAA nanohybrids for antimicrobial applications.

A facile and efficient aqueous phase-based strategy to synthesize silver nanocrystal/graphene nanosheet (GNS) nanohybrids at room temperature, via in situ poly(acrylic acid) (PAA) grafting followed by attachment of Ag nanocrystals, was reported. In the presence of PAA-grafted GNSs, Ag nanoparticles were in situ generated from AgNO(3) aqueous solution without any additional reducing agent or complicated treatment. They readily attached to the GNS surfaces, leading to Ag/GNS-g-PAA nanohybrids. The products of the Ag/GNS-g-PAA nanohybrids were examined by transmission electron microscope, thermogravimetric analyzer, X-ray powder diffraction analyzer, and energy disperse spectroscopy. The Ag nanoparticles can be uniformly deposited on the surfaces of functionalized GNSs with a controlled size distribution of 4-8 nm. Furthermore, the Ag/GNS-g-PAA nanohybrids exhibit good antimicrobial activity against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. The mean diameters of the zones of inhibition are 11.4 mm and 9.9 mm, respectively, for S. aureus and E. coli. The simplicity, efficiency and large-scale availability of nanohybrids combined with good antimicrobial activity make them attractive for graphene-based biomaterials.

Fabrication of carbon nanofiber-polyaniline composite flexible paper for supercapacitor.

In this work we report a low cost technique, via simple rapid-mixture polymerization of aniline using an electrospun carbon nanofiber (CNF) paper as substrate, to fabricate free-standing, flexible CNF-PANI (PANI=polyaniline) composite paper. The morphology and microstructure of the obtained products are characterized by FESEM, FTIR, Raman and XRD. As results, PANI nanoparticles are homogeneously deposited on the surface of each CNF, forming a thin, light-weight and flexible composite paper. The resulting composite paper displays remarkably enhanced electrochemical capacitance compared with the CNF paper, making it attractive for high-performance flexible capacitors.