A trinary support of Ni/NiO/C to immobilize Ir nanoclusters for alkaline hydrogen oxidation.

The hydrogen oxidation reaction is an important process in anion exchange membrane fuel cells with alkaline solutions. The pursuit of efficient catalysts for alkaline hydrogen oxidation has attracted considerable attention. In this study, we present a precursor route for the synthesis of a new Ir-based catalyst (Ir-Ni/NiO/C), in which Ir nanoclusters were immobilized on the generated Ni/NiO/C support derived from a metal-organic framework. The small size of Ir clusters facilitates the exposure of catalytically active sites. The electronic interplay between the Ir nanoclusters and the Ni/NiO/C support optimized the hydrogen binding energy (HBE) and hydroxide binding energy (OHBE) on the surface, which is unattainable on the contrasting Ir-C, Ir-Ni/C, and Ir-NiO/C products. The optimized catalyst shows excellent mass activity for alkaline hydrogen oxidation, which is 3.1 times that of the Pt/C catalyst. This study presents a promising pathway for the development of advanced HOR catalysts.

Nitrogen-Doped Carbon Dots Modified Fe-Co Sulfide Nanosheets as High-Efficiency Electrocatalysts toward Oxygen Evolution Reaction.

Developing high-efficiency and stable oxygen evolution reaction (OER) electrocatalysts is an imperative requirement to produce green and clean hydrogen energy. In this work, the FeCoSy /NCDs composite with nitrogen-doped carbon dots (NCDs) modified Fe-Co sulfide (FeCoSy ) nanosheets is prepared by using a facile and mild one-pot solvothermal method. Benefiting from the low crystallinity and the synergistic effect between FeCoSy and NCDs, the optimal FeCoSy /NCDs-3 composite exhibits an overpotential of only 284 mV at 10 mA cm-2 , a small Tafel value of 52.1 mV dec-1 , and excellent electrochemical durability in alkaline solution. Remarkably, unlike ordinary metal sulfide electrocatalysts, the morphology, components, and structure of the FeCoSy /NCDs composite can be well retained after OER test. The NCDs modified FeCoSy composite with excellent electrocatalytic performance provides an effective approach to boost metal sulfide electrocatalysts for practical application.

Rational Design of High-Performance Electrodes Based on Ferric Oxide Nanosheets Deposited on Reduced Graphene Oxide for Advanced Hybrid Supercapacitors.

The core strategy for constructing ultra-high-performance hybrid supercapacitors is the design of reasonable and effective electrode materials. Herein, a facile solvothermal-calcination strategy is developed to deposit the phosphate-functionalized Fe2O3 (P-Fe2O3) nanosheets on the reduced graphene oxide (rGO) framework. Benefiting from the superior conductivity of rGO and the high conductivity and fast charge storage dynamics of phosphate ions, the synthesized P-Fe2O3/rGO anode exhibits remarkable electrochemical performance with a high capacitance of 586.6 F g-1 at 1 A g-1 and only 4.0% capacitance loss within 10 000 cycles. In addition, the FeMoO4/Fe2O3/rGO nanosheets are fabricated by utilizing Fe2O3/rGO as the precursor. The introduction of molybdates successfully constructs open ion channels between rGO layers and provides abundant active sites, enabling the excellent electrochemical features of FeMoO4/Fe2O3/rGO cathode with a splendid capacity of 475.4 C g-1 at 1 A g-1. By matching P-Fe2O3/rGO with FeMoO4/Fe2O3/rGO, the constructed hybrid supercapacitor presents an admirable energy density of 82.0 Wh kg-1 and an extremely long working life of 95.0% after 20 000 cycles. Furthermore, the continuous operation of the red light-emitting diode for up to 30 min demonstrates the excellent energy storage properties of FeMoO4/Fe2O3/rGO//P-Fe2O3/rGO, which provides multiple possibilities for the follow-up energy storage applications of the iron-based composites.

Construction of NiFe(CN)5NO/Ni3S2 hierarchical submicro-rods on nickel foam as advanced oxygen evolution electrocatalysts.

The development of cheap, abundant, and highly efficient electrocatalysts for the oxygen evolution reaction (OER) is urgently needed for hydrogen production from water splitting. Herein, we demonstrate a novel OER electrocatalyst (NiFe(CN)5NO/Ni3S2) prepared by coupling Ni3S2 and a bimetallic metal-organic framework (MOF) of NiFe(CN)5NO on nickel foam (NF) via a simple two-step route. The NiFe(CN)5NO/Ni3S2 electrocatalyst displays an interesting rod-like hierarchical architecture assembled by ultrathin nanosheets. The combination of NiFe(CN)5NO and Ni3S2 optimizes the electronic structure of the metal active sites and increases the electron transfer capability. Benefitting from the synergistic effect between Ni3S2 and the NiFe-MOF as well as the unique hierarchical architecture, the NiFe(CN)5NO/Ni3S2/NF electrode exhibits excellent electrocatalytic OER activity with ultralow overpotentials of 162/197 mV at 10/100 mA cm-2 and an ultrasmall Tafel slope of 26 mV dec-1 in 1.0 M KOH, which are far superior to those of the individual NiFe(CN)5NO, Ni3S2 and commercial IrO2 catalysts. In particular, unlike common metal sulfide-based electrocatalysts, the composition, morphology and microstructure of the NiFe-MOF/Ni3S2 composite electrocatalyst can be well retained after the OER, which endows it with fantastic long-term durability. This work offers a new strategy for the construction of novel and high-efficiency MOF-based composite electrocatalysts for energy applications.

In Situ Construction of Zn2Mo3O8/ZnO Hierarchical Nanosheets on Graphene as Advanced Anode Materials for Lithium-Ion Batteries.

Transition-metal oxides as anodes for lithium-ion batteries (LIBs) have attracted enormous interest because of their high theoretical capacity, low cost, and high reserve abundance. Unfortunately, they commonly suffer from poor electronic and ionic conductivity and relatively large volume expansion during discharge/charge processes, thereby triggering inferior cyclic performance and rate capability. Herein, a molybdenum-zinc bimetal oxide-based composite structure (Zn2Mo3O8/ZnO/rGO) with rectangular Zn2Mo3O8/ZnO nanosheets uniformly dispersed on reduced graphene oxide (rGO) has been prepared by using a simple and controllable cyanometallic framework template method. The Zn2Mo3O8/ZnO rectangular nanosheets with desirable porous features are composed of nanocrystalline subunits, facilitating the exposure of abundant active sites and providing sufficient contact with the electrolyte. Benefiting from the composition and structural merits as well as the induced synergistic effects, the Zn2Mo3O8/ZnO/rGO composite as LIB anodes delivers superior electrochemical properties, including high reversible capacity (960 mA h g-1 after 100 cycles at 200 mA g-1), outstanding rate performance (417 mA h g-1 at 10,000 mA g-1), and admirable long-term cyclic stability (862 mA h g-1 after 400 cycles at 1000 mA g-1). The mechanism of lithium storage and the formation of SEI film are systematically elucidated. This work provides an effective strategy for synthesizing promising Mo-cluster compound-based anodes for high-performance LIBs.

Molten salt-confined pyrolysis towards heteroatom-doped porous carbon nanosheets for high-energy-density Zn-ion hybrid supercapacitors.

Carbon nanosheets with heteroatom doping and well-developed porosity exhibit broad application foreground for Zn-ion hybrid supercapacitors (ZHSCs), but the simple and controllable preparation is still of great challenge. In this study, by using LiCl-KCl as in-built templates, histidine as carbon and nitrogen sources, and KNO3, K2SO4, KOH or Na2S2O3 as active agent, a series of N and NS doped porous carbon nanosheets are developed. Results indicate that, with the activator introduction, pore structures of the carbonized products are notably boosted, showing an astounding 30-244 % increase in BET specific surface area, and meanwhile, heteroatom with a content of ca. 12 % can be doped into the resultant carbon skeletons. Specifically, the NSPCN-800 (activated by Na2S2O3) with a large specific surface area of 1297 m2/g, a hierarchically porous structure composed of abundant micropores and mesopores, and a suitable heteroatom content (N: 11.9 wt%; S: 0.6 wt%) presents an impressive energy storage behavior as cathode for ZHSCs, including a specific capacitance of 165.8F/g, a specific capacity of 95.2 mAh/g, an energy density of 59.0 Wh kg-1 and a cyclic stability with a 82.6 % capacity retention after 5000 cycles. These performance parameters surpass numerous reported ZHSCs, making NSPCN-800 a very promising cathode for practical use.

N-Doped Carbon as a Promoted Substrate for Ir Nanoclusters toward Hydrogen Oxidation in Alkaline Electrolytes.

Development of effective electrocatalysts toward hydrogen oxidation with a low content of noble metals has attracted the attention of the catalytic community. In this work, a novel catalyst composed of nitrogen-doped carbon acting as the substrate and Ir nanoclusters as active species was prepared, which was then employed as an effective catalyst for the hydrogen oxidation reaction (HOR) in an alkaline electrolyte. In 0.1 M KOH, the optimized catalyst provides an exchange current density of 0.144 mA cmIr-2 for HOR that outperforms the catalytic activity of the commercial Pt/C catalyst with a Pt content of 20 wt %. The substrate induces highly active Ir sites that markedly boosted the electrocatalytic activity for HOR. The nitrogen-doped carbon substrate increases the stability of Ir nanoclusters and decreases the absorption energy of hydrogen on Ir sites; at the same time, the higher electrostatic potential around the adsorbed hydrogen on Ir/N-doped carbon also enables them to be easily attracted by OH- species, both of which enhanced the catalytic activity. The excellent catalytic activity and the understanding shown here will give some hints for the development of HOR catalysts used in alkaline electrolytes.

Morphology-Dependent Electrocatalytic Performance of a Two-Dimensional Nickel-Iron MOF for Oxygen Evolution Reaction.

Developing highly efficient, low-cost, and durable oxygen evolution reaction (OER) electrocatalysts is extraordinarily desirable for achieving clean and sustainable hydrogen energy. Metal-organic frameworks (MOFs) are emerging as attractive candidates for OER electrocatalysts. Herein, a two-dimensional Fe-Ni MOF of Fe(py)2Ni(CN)4 (py = pyridine) is synthesized controllably to generate various nanostructures, including nanoboxes, nanocubes, nanoplates, and nanosheets. Since different morphologies expose different active crystal planes and generate disparate intrinsic active sites, these nanostructures exhibit obviously different electrocatalytic activities. Particularly, the nanoboxes with a hollow structure display superior electrocatalytic activity and stability for OER due to greater active surface area and higher intrinsic activity of the exposed crystal planes, delivering a low overpotential of 285 mV at 10 mA cm-2 and a small Tafel value of 50.9 mV dec-1 in a 1.0 M KOH solution. The morphology-dependent electrocatalytic properties demonstrated in this work provide an efficient strategy to optimize MOF precatalysts for electrochemical energy storage and conversion.

Metal-organic frameworks-derived carbon modified wood carbon monoliths as three-dimensional self-supported electrodes with boosted electrochemical energy storage performance.

Wood-derived carbon monoliths, in recent years, have attracted tremendous interest in the field of energy storage, but their electrochemical characteristics are still far from satisfactory. Here, we report a universal and efficient approach for the preparation of structure-engineered, heteroatom-functionalized and property-boosted wood carbons. A two-step ion-exchange process greatly enriches the nucleation sites of ZIF-8 on the inner wall of wood tracheids, hence leading to a unique carbon/carbon heterostructure after carbonizing and acid-washing. Particularly, the prepared NPCM-900 with a large specific surface area of 708.2 m2 g-1, a hierarchical porous architecture and a suitable N content of 2.3% delivers an ultrahigh area-normalized specific capacitance of 23.7 F cm-2 at 5 mA cm-2, which stands for a new capacitive record among the wood-based binder-free electrodes. The NPCM-900//NPCM-900 all-solid-state supercapacitor has an admirable energy density of 9.3 Wh m-2 at 24.9 W m-2 and a large power density of 248.3 W m-2 at 4.8 Wh m-2, while the NPCM-900 based Zn-ion hybrid supercapacitor (NPCM-900//Zn) exhibits a superior energy density of 12.7 Wh m-2. Furthermore, the NPCM-900//NPCM-900 and NPCM-900//Zn present great stabilities with capacitance retentions of 87% and 85%, respectively, after 5000 cycles. These parameters notably outperform those of most wood-based supercapacitors, endowing the NPCM-900 with extensive prospects for practical use.

Hierarchical flower-like architecture of nickel phosphide anchored with nitrogen-doped carbon quantum dots and cobalt oxide for advanced hybrid supercapacitors.

The exploitation of hybrid supercapacitors with excellent electrochemical properties is of great significance for energy storage systems. Herein, a three-dimensional hierarchical flower-like architecture of nickel phosphide (Ni2P) decorated with nitrogen-doped carbon quantum dots (N-CQDs) and cobalt oxide (Co3O4) is constructed by an effective two-step hydrothermal strategy followed by in situ phosphorization process. Introducing N-CQDs with superior electrochemical characteristics can not only induce the formation of N-CQDs deposited nickel hydroxide (Ni(OH)2) flower-like architecture but also significantly enhance the electrochemical features of Ni(OH)2 nanosheets. After combination with Co3O4 nanoparticles and phosphorization treatment, an advanced cathode of Ni2P/Co3O4/N-CQDs with enriched surface phosphate ions is obtained, which possesses an ultra-high capacity of 1044 C g-1 (2088 F g-1) at 1 A g-1 with a splendid rate capacity of 876 C g-1 (1752 F g-1) at 20 A g-1. Moreover, a device assembled by Ni2P/Co3O4/N-CQDs hierarchical flower-like architecture and p-phenylenediamine functionalized reduced graphene oxide (PPD/rGO) nanosheets depicts a commendable energy density of 53.5 Wh kg-1 at 772.9 W kg-1. This work provides a novel hierarchical multi-component electrode material with decent electrochemical capacities for hybrid supercapacitors, which has a broad prospect in energy storage devices.

Decoration of nickel hexacyanoferrate nanocubes onto reduced graphene oxide sheets as high-performance cathode material for rechargeable aqueous zinc-ion batteries.

Prussian blue analogues (PBA) have attracted much attention in energy research due to their unique three-dimensional open framework structure, adjustable metal ions, and facile synthesis. However, the application of PBA as a cathode material for aqueous zinc-ion batteries (ZIBs) is restricted by its poor cycling performance and lower capacity. In this paper, we develop a new PBA-based hybrid cathode material for aqueous ZIBs by loading uniform nickel hexacyanoferrate (NiHCF) nanocubes onto reduced graphene oxide (RGO) sheets. In the NiHCF/RGO hybrid, NiHCF nanoparticles are well anchored on the RGO layers, forming a conductive network. The strong synergy between NiHCF and highly conductive RGO effectively increases the specific surface area, accelerates the electron and ion transport, and inhibits the structural collapse of the NiHCF/RGO electrode during the Zn2+ insertion/extraction process. Benefiting from the above advantages, the NiHCF/RGO hybrid exhibits a remarkable reversible capacity of 94.5 mAh g-1 at a current density of 5 mA g-1, excellent rate performance of 50.1 mAh g-1 at 200 mA g-1, and enhanced cycling stability with a capacity retention of 80.3% after 1000 cycles at 200 mA g-1. This work provides a simple and effective way to improve the electrochemical performance of PBA-based cathodes for aqueous ZIBs application.

Construction of rGO-Encapsulated Co3 O4 -CoFe2 O4 Composites with a Double-Buffer Structure for High-Performance Lithium Storage.

Transition metal oxides (TMOs) are promising anode materials for next-generation lithium-ion batteries (LIBs). Nevertheless, their poor electronic and ionic conductivity as well as huge volume change leads to low capacity release and rapid capacity decay. Herein, a reduced graphene oxide (rGO)-encapsulated TMOs strategy is developed to address the above problems. The Co3 O4 -CoFe2 O4 @rGO composites with rGO sheets-encapsulated Co3 O4 -CoFe2 O4 microcubes are successfully constructed through a simple metal-organic frameworks precursor route, in which Co[Fe(CN)5 NO] microcubes are in situ coated by graphene oxide sheets, followed by a two-step calcination process. As anode material of LIBs, Co3 O4 -CoFe2 O4 @rGO exhibits remarkable reversible capacity (1393 mAh g-1 at 0.2 A g-1 after 300 cycles), outstanding long-term cycling stability (701 mAh g-1 at 2.0 A g-1 after 500 cycles), and excellent rate capability (420 mAh g-1 at 4.0 A g-1 ). The superior lithium storage performance can be attributed to the unique double-buffer structure, in which the outer flexible rGO shells can prevent the structure collapse of the electrode and improve its conductivity, while the hierarchical porous cores of Co3 O4 -CoFe2 O4 microcubes can buffer the volume expansion. This work provides a general and straightforward strategy for the construction of novel rGO-encapsulated bimetal oxides for energy storage and conversion application.

Anchoring nitrogen-doped carbon quantum dots on nickel carbonate hydroxide nanosheets for hybrid supercapacitor applications.

With the ever-increasing demands for energy resources, the exploration of high energy density hybrid supercapacitors is urgently required. Herein, an effective hydrothermal strategy is demonstrated to construct advanced cathode of nickel carbonate hydroxide (NCH) ultrathin nanosheets anchored nitrogen-doped carbon quantum dots (NCQDs) for hybrid supercapacitors. It is revealed that the NCQDs are evenly deposited on the surface of NCH nanosheets, which provide abundant active sites for NCH nanosheets and endow them improved electrochemical characteristics. The NCH/NCQDs nanosheets deliver a decent electrochemical capacity of 727C g-1 at 1 A g-1 with ameliorative rate capability and cyclic stability. In addition, a hybrid supercapacitor device with an impressive energy density (49.1 Wh kg-1 at 700.3 W kg-1) and stable cycling property (87.5% after 8000 cycles) is fabricated by employing NCH/NCQDs nanosheets and p-phenylenediamine functionalized reduced graphene oxide (PRGO) as cathode and anode. These results indicate the great potential of NCH/NCQDs nanosheets for renewable energy storage.

High energy density hybrid supercapacitor based on cobalt-doped nickel sulfide flower-like hierarchitectures deposited with nitrogen-doped carbon dots.

The exploration of advanced electrode materials with outstanding electrochemical properties is of considerable importance for hybrid supercapacitors but challenging. In this paper, an effective two-step solvothermal route is demonstrated to synthesize nitrogen-doped carbon dots (NCDs) decorated cobalt-doped nickel sulfide (Co-NiS) flower-like hierarchitectures. Because of the modification with NCDs and doping by cobalt atoms, the resulting Co-NiS/NCDs hierarchitectures exhibit an ultrahigh specific capacity up to 1240 C g-1 (2480 F g-1) at 1 A g-1 and a remarkable rate capability of 790.8 C g-1 (1581.6 F g-1) even at 20 A g-1 when used as advanced electrodes for supercapacitors. More significantly, coupling with ap-phenylenediamine (PPD) modified reduced graphene oxide (rGO) anode, a hybrid supercapacitor device is successfully constructed, which possesses an impressive energy density of 71.6 W h kg-1 at 712.0 W kg-1 and a decent cyclic stability with 78.3% retention after 12 000 cycles at 5 A g-1. The dual improvement strategy may provide insight to rational engineering of novel electrode materials with multi-components for high-performance hybrid supercapacitors.

Size-controllable synthesis of Zn2GeO4 hollow rods supported on reduced graphene oxide as high-capacity anode for lithium-ion batteries.

Germanium-based ternary oxides have aroused wide attention as an anode for high-performance lithium-ion batteries (LIBs). Nevertheless, they usually suffer a large volume expansion and rapid capacity fading during lithiation/delithiation cycles. To address this issue, herein, Zn2GeO4/RGO composites are synthesized with Zn2GeO4 hollow rods in-situ grown on reduced graphene oxide (RGO) sheets. The Zn2GeO4 hollow rods can be facilely adjusted from nano- to micro-size. The lithium storage performances of the composites strongly depend on the size of Zn2GeO4 hollow rods and the content of RGO. The optimized Zn2GeO4/RGO composite exhibits a pseudocapacitance-dominated Li+ storage performance, with a large reversible capacity of 1005 mAh g-1 after 100 cycles at 0.5 A g-1, an excellent rate capability (515 mAh g-1 at a high rate of 5 A g-1) and a good long cycling stability of 500 cycles with a low capacity loss of 0.05% per cycle at 1 A g-1. The outstanding electrochemical performance can be attributed to the unique composition and microstructure of the material as well as the synergistic effect of the conductive RGO sheets and the hollow Zn2GeO4 nanostructure. This work provides a promising anode for high-performance LIBs and a useful inspiration for further improving the Ge-based ternary oxide anodes.

A zinc ion yarn battery with high capacity and fire retardancy based on a SiO2 nanoparticle doped ionogel electrolyte.

Ionogel electrolytes are proposed to be an excellent substitute for liquid electrolytes due to their superior portability, flexibility and safety without any leakage that may lead to the failure of batteries. Given these natural characteristics, ionogels can provide batteries with good flexibility and wearability. However, the instability under different extreme working conditions and low ionic conductivity limit the further applications of ionogels. In this research, an ionogel electrolyte is synthesized by polymerizing 1-vinyl-3-ethylimidazolium dicyanamide ([Veim][DCA]) and N,N-methylenebisacrylamide (NNMBA) in zinc acetate (Zn(CH3COO)2) and manganese sulfate (MnSO4) dissolved 1-ethyl-3-methylimidazolium dicyanamide ([Emim][DCA]). The fire retardancy of the ionogel electrolyte is improved by adding SiO2 nanoparticles into the electrolyte. The ionogel electrolyte with 40 wt% silicon dioxide (SiO2) nanoparticles possesses a high ionic conductivity of 0.013 S cm-1 and the zinc//manganese dioxide (Zn//MnO2) battery based on the ionogel electrolyte is able to deliver a high specific capacity of 277 mA h g-1 and a high energy density of 283 W h kg-1. Moreover, the SiO2 nanoparticles contained in the ionogel endow the battery with good fire retardancy. Put together, the yarn battery successfully meets the requirements of modern flexible and wearable electronics.

Nitrogen-doped carbon dots anchored NiO/Co3O4 ultrathin nanosheets as advanced cathodes for hybrid supercapacitors.

Herein, we demonstrate an advanced cathode of nitrogen-doped carbon dots (NCDs) anchored NiO/Co3O4 ultrathin nanosheets for hybrid supercapacitors by a facile hydrothermal-calcination route. Owing to the well defined thin-plate structure and ternary composition, the optimized NiO/Co3O4/NCDs nanosheets demonstrate a high specific capacity of 976.3 C g-1 (1775 F g-1) at 1 A g-1, and a splendid cycling stability of approximately 95.7% retention over 10,000 continuous cycles (15 A g-1). In addition, a hybrid supercapacitor is constructed by using NiO/Co3O4/NCDs nanosheets as cathode and reduced graphene oxide (RGO) supported NCDs composites as anode. The obtained NiO/Co3O4/NCDs//RGO/NCDs hybrid supercapacitor delivers a maximum energy density of 41.6 Wh kg-1, together with outstanding cycling stability (no decay after 10,000 cycles at 10 A g-1). Therefore, the ultrathin sheet-like structured NiO/Co3O4/NCDs cathode presents a great potential for supercapacitor application.

Facile synthesis of novel tungsten-based hierarchical core-shell composite for ultrahigh volumetric lithium storage.

The development of novel high volumetric capacity electrode materials is crucial to the application of lithium-ion batteries (LIBs) in miniaturized consumer electronics. In this work, a novel tungsten-based octahedron (CoWO4/Co3O4) with unique hierarchical core-shell structure is successfully fabricated by simply calcinating a cyanide-metal framework precursor. Benefitting from the heavy element W, the CoWO4/Co3O4 octahedrons show a high mass density of 5.18 g cm-3. When applied as anode materials for LIBs, the CoWO4/Co3O4 octahedrons exhibit an ultrahigh volumetric capacity (6226 mAh cm-3 after 350 cycles at 0.4 A g-1), superior rate capability (3165 mAh cm-3 at 3.0 A g-1) and outstanding long-term cycling performance (4703 mAh cm-3 at 1.0 A g-1 after 800 cycles). The extraordinary lithium storage performance can be ascribed to the unique hierarchical core-shell structure and the possible synergistic effect between W and Co, which provide more Li+ insertion sites and effectively buffer the volume variation during cycling. This work not only provides an ultrahigh volumetric lithium storage anode, but also gives a simple and general strategy for the synthesis of novel anode materials for high volumetric energy density LIBs.

High-Voltage Flexible Aqueous Zn-Ion Battery with Extremely Low Dropout Voltage and Super-Flat Platform.

Flexible rechargeable aqueous zinc-ion batteries (ZIBs) have attracted extensive attentions in the energy storage field due to their high safety, environmental friendliness, and outstanding electrochemical performance while the exploration of high-voltage aqueous ZIBs with excellent rate capability is still a great challenge for the further application them in flexible and wearable electronics. Herein, we fabricated a 2.4 V high-voltage flexible aqueous ZIB, being among the highest voltage reported in aqueous ZIBs. Moreover, it exhibits extremely flat charging/discharging voltage platforms and the dropout voltage is only 0.1 V, which is the smallest gap in all aqueous batteries to our best knowledge. Furthermore, the prepared ZIB performs high rate capability of 25 C and energy density of 120 Wh kg-1 and exhibits excellent safety under various destructive conditions including hammering, sewing, punching, and soaking. These extraordinary results indicate the great application potential of our high-voltage flexible aqueous ZIB in wearable electronics.

MOF derived CoP-decorated nitrogen-doped carbon polyhedrons/reduced graphene oxide composites for high performance supercapacitors.

ZIF-67 derived CoP-decorated nitrogen-doped porous carbon (CoP-NPC) polyhedra anchored on reduced graphene oxide (RGO) sheets have been successfully prepared through an efficient pyrolysis-phosphidation-assembly strategy. The resulting CoP-NPC/RGO composite as an electrode for supercapacitors shows an enhanced electrochemical performance with high capacitances of 466.6 F g-1 at 1 A g-1 and 252 F g-1 at 20 A g-1, as well as 94.7% of capacitance retention after 10 000 cycles in 1 M H2SO4 solution. Moreover, the symmetrical two-electrode device assembled from CoP-NPC/RGO electrodes delivers a high energy density of 12 W h kg-1 at a power density of 500 W kg-1 and excellent long-term cycling stability (93% of the initial capacitance after 10 000 cycles at 10 A g-1). This superior electrochemical performance of CoP-NPC/RGO can be ascribed to its 3D interconnected porous structure and the synergistic effect between CoP and the nitrogen-doped carbon matrix. The unique architecture of the composites can effectively enhance the electrochemical performance by shortening the diffusion distance of electrolyte ions and improving the electrical conductivity and the contact area between active materials and the electrolyte. The excellent electrochemical performances make CoP-NPC/RGO a promising electrode material for high-performance supercapacitors.