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To improve the complexity and low catalytic performance and reduce the high cost of the traditional electrode preparation process for the sodium borohydride electro-oxidation reaction (BOR), in this work, a self-supported and efficient electrode material grown on nickel foam (CoNi/Co3O4/NF) was successfully designed using a simple hydrothermal synthesis method accompanied by the electrodeposition process. Benefiting from the three-dimensional nanoarray structure of CoNi/Co3O4/NF and the uniform distribution of Co and Ni modulating active sites by electrodeposition, the catalytic activity towards NaBH4 exhibits high efficiency. CoNi/Co3O4 exhibits excellent catalytic performance (up to 2157 mA cm−2 in 2 mol L−1 NaOH and 0.3 mol L−1 NaBH4), a high electrochemically active surface area (62.5 cm−2), and a low activation energy (15.56 kJ mol−1). The CoNi/Co3O4/NF electrode was further investigated on a direct sodium borohydride–hydrogen peroxide fuel cell (DBHPFC), which exhibited a maximum power density of 108.5 mW cm−2 and excellent stability. The excellent performance is mainly due to its unique nanoarray structure and electrodeposition distribution of Co and Ni active sites, which increases the electrochemical surface area and enhances the contact between the electrode and the electrolyte. [ABSTRACT FROM AUTHOR]

The non-uniform plating–stripping behaviours of Li metal anodes hinder the application of Li metal batteries. Here, a stable 3D matrix is designed by coating a carbon skeleton with MXene, and the significant influence of the crystallographic texture of Li metal on electrochemical behaviour is investigated. The results demonstrate that the 3D MXene/carbon skeleton can effectively induce the evolution of advantageous Li(110) facets with a dendrite-free anode interface. Consequently, the modified Li metal anodes deliver stable plating–stripping behaviours. [ABSTRACT FROM AUTHOR]

Urea electrolysis is an appealing energy conversion technology to produce hydrogen (H2) and alleviate the problem of urea-rich wastewater treatment concurrently. In particular, electrocatalytic performance can be dramatically enhanced by rationally modulating the surface charge distribution with a well-tuned heterostructure. Herein, a heterostructure is constructed by NiMoO4 nanosheets grown on an interior hollow NiS@Ni3S2 nanorods framework (NiS@Ni3S2/NiMoO4). Density functional theory (DFT) calculations demonstrate that the formed heterojunction structure leads to a tailored surface charge state of NiMoO4, with oxygen as the nucleophilic region and molybdenum as the electrophilic region, which facilitates the decomposition of urea molecules and thus significantly improves hydrogen evolution. As expected, the assembled NiS@Ni3S2/NiMoO4 system substantially expedites urea electrolysis activity with a cell voltage of 1.40 V at 10 mA cm−2, which is 200 mV less than the voltage of an overall water splitting system. [ABSTRACT FROM AUTHOR]

Herein, a three-dimensional (3D) Ni/Fe bimetallic organic framework (MOF-Ni@MOF-Fe) with a structure of rhombus blocks on nanosheets is synthesized on Ni foam by a 2-step solvothermal method. After sulfide reaction, MOF-Ni@MOF-Fe–S is vulcanized by MOF-Ni@MOF-Fe with a structure of interwoven and folding nanosheets. Meanwhile, Ni3S2 is formed under the influence of iron. This special structure makes MOF-Ni@MOF-Fe–S to expose more active sites. MOF-Ni@MOF-Fe–S shows superior urea oxidation reaction (UOR) and hydrogen evolution reaction (HER) performance. When MOF-Ni@MOF-Fe–S is used as UOR and HER catalysts, it has low potentials of 1.347 V (vs. RHE) at 10 mA cm−2 and 0.145 V (vs. RHE) at 10 mA cm−2 in 1.0 M KOH with 0.5 M urea, respectively. MOF-Ni@MOF-Fe–S as a bifunctional electrode is assembled as an alkaline urea electrolyzer, showing catalytic activity at a low cell voltage of 1.539 V at 10 mA cm−2 and excellent stability during 10 h chronopotentiometry analysis. [ABSTRACT FROM AUTHOR]

Designing and exploring earth-abundant but high-performance electrode materials are of crucial significance for the future large-scale development of supercapacitors. Herein, a facile anionic P-substitution strategy is used to in situ decorate ternary Ni–S–P nanoparticles on graphene nanosheets (G/Ni–S–P) for supercapacitors for the first time. Benefitting from the unique hierarchical structure and positive synergistic effects between each component, the resultant G/Ni–S–P composite delivers a spectacular specific capacity of 1406 C g−1 at 1 A g−1 with an outstanding rate capability of 60.2% at 120 A g−1, which is highly superior to those of the previously reported nickel based composites. The asymmetric supercapacitor assembled with the G/Ni–S–P and graphene/FeOOH composite as the cathode and anode exhibits high energy density up to 58.1 W h kg−1 and superb electrochemical stability with 4.9% decay after 30 000 continuous charge/discharge cycles. These intriguing electrochemical performances indicate that the G/Ni–S–P composite has enormous potential application in high-performance energy storage systems in the future. [ABSTRACT FROM AUTHOR]

Urea electrolysis offers the prospect of cost-effective and energy-saving hydrogen production together with mitigating urea-rich wastewater pollution instead of overall water splitting. Hence, here, high-efficiency bifunctional electrocatalysts were developed for both the urea oxidation reaction (UOR) and hydrogen evolution reaction (HER) via the in situ vertical growth of thorny leaf-like (2D nanosheets supporting 1D nanowires) NiCoP on a carbon cloth (NiCoP/CC). After integrating the advantages of the synergistic effect between Ni and Co as well as the unique hierarchical structure combined with 1D nanowires, 2D nanosheets and a 3D conductive carbon cloth substrate, the electrode exhibited excellent electrocatalytic activity toward HER and UOR. The electrolytic cell assembled using NiCoP/CC as the anode and the cathode could provide current density of 10 mA cm−2 at a cell voltage of 1.42 V (160 mV less than that for its urea-free counterpart) as well as remarkable durability over 30 h. Thus, the cost-effectiveness and high activity of the NiCoP/CC electrode pave the way to explore transition metal-based electrocatalysts for urea electrolysis. [ABSTRACT FROM AUTHOR]

Li-ion and K-ion batteries present their unique advantages of high energy density and low cost, respectively. It is a challenge to explore a universal anode with efficient electrochemical performance. Herein, a two-dimensional TiO2/reduced graphene oxide (RGO) composite was prepared by a facile hydrothermal method. TiO2 nanoparticles are transformed from Ti2C MXene and connect the RGO nanosheets to form a sheet-like structure. Serving as the anode material, the TiO2/RGO presents high capacity, remarkable rate ability and long cycling performance for both Li- and K-ion batteries. The superior electrochemical performance is attributed to the short ion diffusion path due to the small particle size (15–25 nm) and the highway for electron transport provided by RGO. In addition, RGO motivates the capacitive contribution, resulting in enhanced capacity and better rate performance. Meanwhile, the electrochemical kinetics of Li/K-ion storage was investigated by quantitative kinetics analysis. This work demonstrates a possibility to introduce the capacitive capacity to realize rapid ion storage and improve the cycling stability, providing a new strategy to design efficient electrodes for metal-ion batteries. [ABSTRACT FROM AUTHOR]

Sodium ion hybrid capacitors (SHCs) using battery-type and capacitor-type electrodes are designed to obtain both high energy and power densities. However, anode materials commonly cannot meet the high capacity and rapid charging/discharging stability requirements. With the help of sandwiched design, herein novel porous carbon microtubes are sandwiched by vertical ultrasmall-sized SnS nanosheets (SnS/aCMT) via combined solvothermal and thermal-treatment approaches. The three-dimensional interconnected SnS nanosheet network grown on both sides of the hollow carbon microtubes could greatly prevent their aggregation and facilitate ion transport, which endows the anode material with improved specific capacity and structural stability. As a result, the SnS/aCMT electrode presents high capacity (517 mA h g−1 at 0.1 A g−1) and remarkable rate capability (306 mA h g−1 even at 5 A g−1) as well as long-term cycling stability with 88.7% retention over 500 cycles. Furthermore, a SHC, assembled by using SnS/aCMT as the anode and aCMT as the cathode, presents a high energy density of 115 W h kg−1 in the voltage range of 0.5–4.0 V and stable long-term cycling performance. [ABSTRACT FROM AUTHOR]

Developing cost-efficient and effective catalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) remains a great challenge for application in high-efficiency water electrolyzers. In this work, we design a highly efficient and durable water splitting system in an alkaline solution, in which platinum (Pt) sub-nanocluster (average size: 0.59 nm) functionalized nickel–iron layered double hydroxide nanosheets on carbon fiber cloth (Pt–NiFe LDH/CC) serve as the cathode and hierarchical (Ni0.77Fe0.23)Se2 nanosheets on CC ((Ni0.77Fe0.23)Se2/CC) act as the anode. For the HER, the three-dimensional (3D) Pt–NiFe LDH/CC electrode with an ultralow Pt content (1.56 wt%) drives a current density of 10 mA cm−2 at an ultralow overpotential of 28 mV. For the OER, the edge-rich (Ni0.77Fe0.23)Se2/CC electrode displays a current density of 10 mA cm−2 at a small overpotential of 228 mV, and the Tafel slope is as low as 69 mV dec−1. More importantly, the assembled Pt–NiFe LDH/CC☋☋(Ni0.77Fe0.23)Se2/CC water splitting electrolyzer exhibits a high current density of 30 mA cm−2 at a low cell voltage of 1.57 V, which is superior to that of the electrolyzer assembled using commercial 20 wt% Pt/C and RuO2 electrodes (30 mA cm−2 at 1.62 V). Additionally, the Pt–NiFe LDH/CC☋☋(Ni0.77Fe0.23)Se2/CC electrolyzer displays excellent stability over 40 h even at a high current density of 50 mA cm−2, which shows its great potential in the practical applications of full water splitting. [ABSTRACT FROM AUTHOR]

To balance the electrochemical performance gap between the Li+ insertion/deintercalation anode and the anion adsorption/desorption cathode, in this paper, for the first time, we investigated MnNb2O6 as a new rate capability type anode material for lithium-ion capacitors (LICs). Novel calendula-like MnNb2O6 particles anchored on reduced graphene oxide (rGO) were prepared via a simple two-step hydrothermal route. The special three-dimensional structure and cross-linked conductive network constructed by graphene could shorten the lithium-ion diffusion path, efficiently facilitate electron transmission and adapt to volume strain without shedding during the long-term charge/discharge process. This resulted in excellent charge storage capacity and reasonably superior cycling stability. MnNb2O6@rGO//AC LICs assembled with MnNb2O6@rGO as the cathode and activated carbon (AC) as the anode exhibited excellent performance with maximum energy density of 118 W h kg−1 and power density of 8000 W kg−1 based on the total mass loading of the active material weight. The initial capacity retention was up to 88% after 10 000 charge/discharge cycles, which was higher than that of bimetallic oxide materials reported so far. Therefore, this study might provide a novel rate capability anode material for LICs with high performance. [ABSTRACT FROM AUTHOR]

Incorporation of reduced graphene oxide (rGO) optimizes the interfacial properties of MgMn2O4 and improves the Mg2+ diffusion in the electrode. This results in enhanced specific capacity and rate capability. MgMn2O4/rGO nanocomposites show a large discharge specific capacity of 140.1 mA h g−1 at a current density of 1000 mA g−1. [ABSTRACT FROM AUTHOR]

In our work, we successfully design boron (B) and nitrogen (N) co-doped porous carbon tube bundle (B/N-PCTB) electrode materials which are directly derived from the biomass of dandelion fluff. The low-tortuosity, and open and porous structures contribute to electron transport along the tube wall and unimpeded ion diffusion inside the carbon tubes. The incorporation of heteroatoms into PCTBs can bring extra pseudocapacitance and double layer capacitance to enhance the overall capacitance. Benefiting from the hollow and open microstructure and heteroatom doping, the optimized B/N-PCTB electrode (active materials: 2.6 mg cm−2) possesses an impressive specific capacitance of 355 F g−1 at 1 A g−1. Even with an ultrahigh loading mass of 40 mg cm−2, the electrode still has a relatively high specific capacity of 216 F g−1 at 1 A g−1. The assembled symmetric cell with an active material loading of 80 mg cm−2 (cathode: 40 mg cm−2; anode: 40 mg cm−2) shows a superior volumetric energy density of 12.15 W h L−1 at the power density of 699.84 W L−1. The facile yet high-performance porous carbon tube bundle is a promising material which can be applied in many other fields such as lithium ion batteries, hydrogen evolution reaction, and heavy metal ion adsorption. [ABSTRACT FROM AUTHOR]

A three-dimensional (3D) catalyst electrode of Co3O4 nanosheets in situ formed on reduced graphene oxide modified Ni foam (Co3O4/rGO@Ni foam) for H2O2 electroreduction is prepared by a two-step hydrothermal method. In the first step, graphene oxide sheets are reduced and formed on the skeleton of Ni foam and Co3O4 nanosheets are synthesized intermixed with the rGO sheets through the second step. The Co3O4 nanosheets are made up of plentiful nanoparticles and there are many nanoholes among these nanoparticles which are beneficial for the sufficient contact between H2O2 and the catalyst. The morphology and phase composition of the Co3O4/rGO@Ni foam electrode are studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrocatalytic activity of the as-prepared electrode is investigated by cyclic voltammetry (CV) and chronoamperometry (CA). From the results, it can be seen that in 2 mol L−1 NaOH and 0.5 mol L−1 H2O2, the reduction current density of H2O2 on the Co3O4/rGO@Ni foam electrode is 450 mA cm−2 at −0.8 V which is much higher than that on Co3O4 directly supported on Ni foam. This obvious increase of the current density can be attributed to the increase of the surface area of the electrode after the addition of rGO. Also, the interpenetration of rGO and Co3O4 nanosheets improves the electron and ion transport ability of the electrode which leads to a good electrocatalytic activity and stability of the Co3O4/rGO@Ni foam electrode. [ABSTRACT FROM AUTHOR]

One-dimensional (1D) nanostructures have been identified as the most viable structures for high-performance supercapacitors from the view of high ion-accessible surface area and rapid electron transport path as well as excellent mechanical properties. Herein, we report a “stripping and cutting” strategy to produce 1D carbon nanobelts (CNB) from tofu with irregular structures through a molten salts assisted technique. It is a completely novel and green avenue for constructing 1D carbon materials from biomass, showing large commercial potential. The resultant CNB electrode delivers a high specific capacitance (262 F g−1 at 0.5 A g−1) and outstanding cycling stability with capacitance retention up to 102% after 10 000 continuous charging/discharging cycles. Additionally, a CNB//CNB symmetric supercapacitor and CNB//MnO2–CNB asymmetric supercapacitor are assembled and reach energy densities of 18.19 and 29.24 W h kg−1, respectively. Therefore, such a simple, one-pot and low-cost process may have great potential for preparing eco-friendly biomass-derived carbon materials for high-performance supercapacitor electrodes. [ABSTRACT FROM AUTHOR]

Three-dimensional Ni(OH)2/Ni foam electrodes with low cost are simply fabricated via a template-free growth method and employed as efficient anodes for a direct urea–hydrogen peroxide fuel cell (DUPFC). The surface morphologies of Ni(OH)2 catalysts on the electrodes can be easily controlled by altering the reaction temperatures. The nano-sheet (NS) Ni(OH)2/Ni foam electrode exhibits highest catalytic activity towards urea electro-oxidation among the four electrodes. The oxidation current density of the NS Ni(OH)2/Ni foam electrode reaches 337 mA cm−2 at 0.45 V (vs. Ag/AgCl) with a low onset oxidation potential in 0.6 mol L−1 urea and 5 mol L−1 KOH solutions. The DUPFC using NS Ni(OH)2/Ni foam anode shows an open circuit voltage of 0.86 V and high peak power density of 19.7 mW cm−2 and 28.8 mW cm−2 at 20 °C and 50 °C, respectively, which is much higher than the performance of direct urea fuel cells reported previously. The outstanding cell performance using a cheap NS Ni(OH)2/Ni foam anode indicates DUPFC is a promising new type of fuel cell. [ABSTRACT FROM AUTHOR]

To meet the ever-increasing need for high-efficiency energy storage in modern society, porous carbon materials with large surface areas are typically employed for electrical double-layer capacitors to achieve high gravimetric performances. However, their poor volumetric performances come from low packing density and/or high pore volume resulting in poor volumetric capacitance, which would limit their further applications. Here, a novel and one-step molten salt synthesis of a three-dimensional, densely nitrogen-doped porous carbon (NPC) material by using low-cost and eco-friendly tofu as the nitrogen-containing carbon source is proposed. Hierarchically porous carbon with a specific surface area of 1202 m2 g−1 and a high nitrogen content of 4.72 wt% and a bulk density of ∼0.84 g cm−3 is obtained at a carbonation temperature of 750 °C. As the electrode material for a supercapacitor, the NPC electrode shows both ultra-high specific volumetric and gravimetric capacitances of 360 F cm−3 and 418 F g−1 at 1 A g−1 (based on a three-electrode system), respectively, and excellent cycling stability without capacitance loss after 10 000 cycles at a high charge current of 10 A g−1 in KOH electrolyte. Moreover, the as-assembled symmetric supercapacitor exhibits not only an excellent cycling stability with 97% capacitance retention after 10 000 cycles, but also a high volumetric energy density up to 27.68 W h L−1 at a current density of 0.2 A g−1, making this new method highly promising for compact energy storage devices with simultaneous high volumetric/gravimetric energy and power densities. [ABSTRACT FROM AUTHOR]

Large surface area, high electrical conductivity, and abundant channels have been recognized to favor faradic capacitors, but their realization at the same time by a facile preparation process is still a great challenge. Here, we synthesized porous cadmium sulphide freely standing on nickel foam (CdS/NF) via a one-step hydrothermal method which possesses high specific capacitance, good rate capability and outstanding cycling stability. The CdS/NF microspheres present pores with a mean size of ∼3 nm, resulting in fast diffusion of ions, facile transportation of electrons and high activity, which make great synergistic contributions to reversible redox reactions. In the resulting supercapacitors, a specific capacitance of 909 F g−1 is achieved at a current density of 2 mA cm−2 with excellent rate capability that 88% of the original capacitance is retained at 50 mA cm−2. After 5000 charge–discharge cycles at current densities as large as 50 mA cm−2, 104% of initial capacitance is maintained. Finally, asymmetric supercapacitors with a high energy density of 28 W h kg−1 at a power density of 160 W kg−1 were obtained. [ABSTRACT FROM AUTHOR]

A low-cost and binder-free cobalt electrode is prepared by the electrodeposition of Co nanoplates onto a flexible conductive substrate, which is prepared simply by scratching a piece of A4 paper with a common 8B pencil. The morphology and phase structure of the cobalt–graphite–paper (CGP) electrode are characterized by scanning electron microscopy, transmission electron microscopy and an X-ray diffractometer. The catalytic activity of the CGP electrode for NaBH4 electro-oxidation is investigated by cyclic voltammetry and chronoamperometry. The catalyst combines tightly with the paper and exhibits a good stability. The oxidation current density reaches up to 180 mA cm−2 in 1 mol dm−3 NaOH and 0.10 mol dm−3 NaBH4 at −0.4 V. [ABSTRACT FROM AUTHOR]

Correction for ‘Ultrasmall-sized SnS nanosheets vertically aligned on carbon microtubes for sodium-ion capacitors with high energy density’ by Jing Zhao et al., J. Mater. Chem. A, 2019, 7, 4047–4054. [ABSTRACT FROM AUTHOR]

We report a flash Joule heating method for the rapid preparation of graphene-like materials. The L-GHS exhibited a uniform diameter of 200 nm and an ideal specific surface area of 670 m 2 g -1 . Meanwhile, the specific capacity of L-GHS remained at 942 mA h g -1 after 600 cycles (1 A g -1 ), which shows excellent electrochemical performance.

Potassium-ion batteries (PIBs) as a promising and low-cost battery technology offer the advantage of utilizing abundant and cost-effective K-salt sources. However, the effective adoption of PIBs necessitates the identification of suitable electrode materials. The 1T phase of MoS 2 exhibits enhanced electronic conductivity and greater interlayer spacing compared to the 2H phase, leading to a capable potassium ion storage ability. Herein, we fabricated dual carbon engineered 1T/2H MoS 2 via a secure and straightforward ammonia-assisted hydrothermal method. The 1T/2H MoS 2 @rGO@C structure demonstrated an expanded interlayer spacing (9.3 Å). Additionally, the sandwich-like structural design not only enhanced material conductivity but also effectively curbed the agglomeration of nanosheets. Remarkably, 1T/2H MoS 2 @rGO@C exhibited impressive potassium storage ability, delivering capacities of 351.0 mA h g -1 at 100 mA g -1 and 233.8 mA h g -1 at 1000 mA g -1 following 100 and 1000 cycles, respectively. Moreover, the construction of a K-ion full cell was successfully achieved, utilizing perylene tetracarboxylic dianhydride (PTCDA) as the cathode, and manifesting a capacity of 294.3 mA h g -1 at 100 mA g -1 after 160 cycles. This underscores the substantial potential of employing the 1T/2H MoS 2 @rGO@C electrode material for PIBs.

Herein, a three-dimensional (3D) Ni/Fe bimetallic organic framework (MOF-Ni@MOF-Fe) with a structure of rhombus blocks on nanosheets is synthesized on Ni foam by a 2-step solvothermal method. After sulfide reaction, MOF-Ni@MOF-Fe-S is vulcanized by MOF-Ni@MOF-Fe with a structure of interwoven and folding nanosheets. Meanwhile, Ni 3 S 2 is formed under the influence of iron. This special structure makes MOF-Ni@MOF-Fe-S to expose more active sites. MOF-Ni@MOF-Fe-S shows superior urea oxidation reaction (UOR) and hydrogen evolution reaction (HER) performance. When MOF-Ni@MOF-Fe-S is used as UOR and HER catalysts, it has low potentials of 1.347 V (vs. RHE) at 10 mA cm -2 and 0.145 V (vs. RHE) at 10 mA cm -2 in 1.0 M KOH with 0.5 M urea, respectively. MOF-Ni@MOF-Fe-S as a bifunctional electrode is assembled as an alkaline urea electrolyzer, showing catalytic activity at a low cell voltage of 1.539 V at 10 mA cm -2 and excellent stability during 10 h chronopotentiometry analysis.

Incorporation of reduced graphene oxide (rGO) optimizes the interfacial properties of MgMn2O4 and improves the Mg2+ diffusion in the electrode. This results in enhanced specific capacity and rate capability. MgMn2O4/rGO nanocomposites show a large discharge specific capacity of 140.1 mA h g-1 at a current density of 1000 mA g-1.

A three-dimensional (3D) catalyst electrode of Co 3 O 4 nanosheets in situ formed on reduced graphene oxide modified Ni foam (Co 3 O 4 /rGO@Ni foam) for H 2 O 2 electroreduction is prepared by a two-step hydrothermal method. In the first step, graphene oxide sheets are reduced and formed on the skeleton of Ni foam and Co 3 O 4 nanosheets are synthesized intermixed with the rGO sheets through the second step. The Co 3 O 4 nanosheets are made up of plentiful nanoparticles and there are many nanoholes among these nanoparticles which are beneficial for the sufficient contact between H 2 O 2 and the catalyst. The morphology and phase composition of the Co 3 O 4 /rGO@Ni foam electrode are studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrocatalytic activity of the as-prepared electrode is investigated by cyclic voltammetry (CV) and chronoamperometry (CA). From the results, it can be seen that in 2 mol L -1 NaOH and 0.5 mol L -1 H 2 O 2 , the reduction current density of H 2 O 2 on the Co 3 O 4 /rGO@Ni foam electrode is 450 mA cm -2 at -0.8 V which is much higher than that on Co 3 O 4 directly supported on Ni foam. This obvious increase of the current density can be attributed to the increase of the surface area of the electrode after the addition of rGO. Also, the interpenetration of rGO and Co 3 O 4 nanosheets improves the electron and ion transport ability of the electrode which leads to a good electrocatalytic activity and stability of the Co 3 O 4 /rGO@Ni foam electrode.