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MXenes have attracted great interests as supercapacitors due to their metallic conductivity, high density, and hydrophilic nature. Herein we report Ti3C2‐Cu/Co hybrids via molten salt etching in which the existence of metal atoms and their interactions with MXene via surficial O atoms were elucidated by XAFS for the first time. The electrochemical investigation of Ti3C2‐Cu electrode demonstrated the pseudocapacitive contribution of Cu and a splendid specific capacitance of 885.0 F g−1 at 0.5 A g−1 in 1.0 M H2SO4. Symmetric supercapacitor Ti3C2‐Cu//Ti3C2‐Cu was demonstrated with operating voltage of 1.6 V, areal capacitance of 290.5 mF cm−2 at 1 mA cm−2, and stability over 10 000 cycles. It delivered an areal energy density of 103.3 μWh cm−2 at power density of 0.8 mW cm−2, based on which a supercapacitor pouch was fabricated. It provides deeper insights into the molten salt mechanism and strategies for designing MXene‐based materials for electrochemical energy storage. [ABSTRACT FROM AUTHOR]

In this paper, the water-soluble PEDOT:PSS film not only increases the toughness of the rGO/CoFe 2 O 4 /PEDOT:PSS paper but also increases the wettability. The device can be charged in both positive and negative directions, and when change charging direction, the electrochemical performance of the device is also excellent. [Display omitted] • The water-soluble PEDOT:PSS film not only increases the toughness of the rGO/CoFe 2 O 4 /PEDOT:PSS paper but also increases the wettability. • The rGO/CoFe 2 O 4 /PEDOT:PSS paper as electrodes of supercapacitor has high specific capacitance of 229.6 mF cm−2 at current density 1 mA cm−2. • The symmetric supercapacitor shows the energy density of 25.9 Wh kg−1 at power density of 135.3 W kg−1. • The device can be charged in both positive and negative directions, and when change charging direction, the electrochemical performance of the device is also excellent. Nowadays, safe, toughness, flexible and wearable energy storage devices have become a research hotspot. However, the safety and stability of flexible devices are still challenging because traditional wearable energy storage devices are difficult to overcome the problems of leakage, toxic and fragile electrolyte and so on. In this study, we successfully designed and constructed a continuous porous conductive polymer PEDOT:PSS film coated graphene (rGO) and CoFe 2 O 4 nanospheres composite paper electrode material. rGO paper has the advantages of good electrical conductivity and large surface area, but the graphene sheet without oxygen group has very weak adhesion between sheets, and the surface is completely hydrophobic. The water-soluble conductive polymer PEDOT:PSS film successfully increased the toughness and wettability of the graphene composite paper, and the kinetic fitting verified that the polymer improved the rate performance and electrochemical activity of the graphene composite paper. The area specific capacitance, energy density and power density of the symmetric supercapacitor made of rGO/CoFe 2 O 4 /PEDOT:PSS paper are 229.6 mF cm−2, 25.9 Wh kg−1 and 135.3 W kg−1. More importantly, the device can be charged in both positive and negative directions, and when change charging direction, the electrochemical performance of the device is also excellent. This solves the safety problem caused by the wrong connection between positive and negative poles of the supercapacitor, and also makes a contribution to the safety development of flexible supercapacitors. [ABSTRACT FROM AUTHOR]

In this paper, we report a system of electrochemical polymerization to prepare a porous polymer nanolayer coated nanomaterial Co(CO 3) 0.5 (OH) (CoCHH)/PEDOT electrode with interwoven porous network structure. The PEDOT nanolayer has the advantages of controllable thickness, good electrical conductivity, porous and continuous. In addition, each unit of the special structure can be uniformly coated by nanolayer, and prevent the internal nanostructure from collapsing of the structure as electrolyte ions move in and out, and the conductivity and porosity of the composite electrode can be improved. [Display omitted] • The CC/CoCHH/PEDOT has unique interwoven porous network structure. • The PEDOT nanolayer has good electrical conductivity, porous and continuous. • The CC/CoCHH/PEDOT as cathode has specific capacitance of 1520 F g−1. • The asymmetric supercapacitor shows the energy density of 70.8 Wh kg−1. A common approach to research supercapacitors is to choose a special structure of nanomaterials combined with noble metal oxides to increase capacity. However, using precious metals as electrodes with special nanostructures is both expensive from a commercial point of view and detrimental to the commercialization of supercapacitors. Therefore, we report a system of electrochemical polymerization to prepare a porous polymer nanolayer coated nanomaterial Co(CO 3) 0.5 (OH) (CoCHH)/PEDOT electrode with interwoven porous network structure. The PEDOT nanolayer has the advantages of controllable thickness, good electrical conductivity, porous and continuous. In addition, each unit of the special structure can be uniformly coated by nanolayer, and prevent the internal nanostructure from collapsing of the structure as electrolyte ions move in and out, and the conductivity and porosity of the composite electrode can be improved. As a result, the positive electrode of the composite nanolayer system showed excellent stability, with capacitance retention of 92.7% after 2000 cycles. [ABSTRACT FROM AUTHOR]

In this paper, the electrochemical hydrolysis (ECH) system can be formed by using Co(OH) 2 /Co 3 S 4 nanorod and Co(OH) 2 /CoSe 2 heterostructure nanotube as electrocatalysts and as-prepared supercapacitors in series, and the water decomposition can be driven directly by the supercapacitor. The electrochemical hydrolysis effect is obvious, and significantly improves the performance of the electrochemical hydrolysis system. [Display omitted] • We synthesize Co(OH) 2 /Co 3 S 4 and Co(OH) 2 /CoSe 2 heterostructures. • Morphology, structure and performance of composites are controllable. • The Co(OH) 2 /CoSe 2 cathode has high specific capacity of 1238.3 C g−1. • The asymmetric supercapacitor shows the energy density of 68.9 Wh kg−1. A novel hierarchical porous Co(OH) 2 /CoSe 2 heterostructure composites are prepared by ion exchange method, and the precursor Co(CO 3) 0.5 (OH)∙0.11H 2 O (CoCHH) is synthesized by hydrothermal method. Because the precursor CoCHH has the advantages of mild preparation conditions and controllable morphology and structure, it is possible to prepare a complex hierarchical structure of Co(OH) 2 /CoSe 2. The porous Co(OH) 2 /CoSe 2 heterostructure nanosheet and Co(OH) 2 /CoSe 2 heterostructure nanotube have an excellent specific surface area of 90.5 m2 g−1 and 78.7 m2 g−1, which is significantly better than the precursor CoCHH nanosheet and CoCHH nanorod. The porous Co(OH) 2 /CoSe 2 heterostructure nanosheet as cathode of supercapacitor has high specific capacity of 1283.3 C g−1 at current density 1 A g−1 in 3 M KOH solution, and the Co(OH) 2 /CoSe 2 heterostructure nanotube only required 48 mV (vs. Reversible Hydrogen Electrode) to reach the 10 mA cm−2 for HER in 1 M KOH solution. In addition, with porous Co(OH) 2 /CoSe 2 heterostructure nanosheet as cathode and CNTs as anode, the as prepared asymmetric supercapacitor has satisfactory energy density (68.9 Wh kg−1 at power density of 189.7 W kg−1). Moreover, the electrochemical hydrolysis (ECH) system can be formed by using Co(OH) 2 /Co 3 S 4 nanorod and Co(OH) 2 /CoSe 2 heterostructure nanotube as electrocatalysts and as-prepared supercapacitors in series, and the water decomposition can be driven directly by the supercapacitor. The electrochemical hydrolysis effect is obvious, and significantly improves the performance of the electrochemical hydrolysis system. [ABSTRACT FROM AUTHOR]

As a battery-type electrode material, Ni(OH) 2 has been widely concerned for its ultra-high theoretical specific capacity, however, its poor conductivity and lack of effective active sites hinder its application. It is a great challenge to develop Ni(OH) 2 based supercapacitors. It is critical to improve the electrical conductivity and effective active sites to make full use of the energy storage of Ni(OH) 2 -based materials. Therefore, Ni(OH) 2 /NiS composites are designed and prepared by controllable low temperature chemical deposition and ion exchange method. Ni(OH) 2 nanosheets with various morphology are controllably prepared by low temperature chemical deposition, and then Ni(OH) 2 /NiS composites are controllably prepared on Ni(OH) 2 substrate by ion exchange. Due to the doping of NiS into Ni(OH) 2 nanosheets, the conductive network structure is formed, which makes the composite exhibit excellent electrochemical properties, such as high specific capacity, large specific surface area and good electrical conductivity. The as-fabricated Ni(OH) 2 /NiS indicates an outstanding specific capacity of 240.5 mAh g−1 at 1 A g−1. This paper detailed studies the practical application of hybrid supercapacitors, which may inspire future researchers to design Ni(OH) 2 -based materials with desired applications. 1 Ni(OH) 2 nanosheet is controllably prepared by chemical deposition. 2 The sulfuretted degree of Ni(OH) 2 /NiS is controllable. 3 Ni(OH) 2 /NiS has excellent specific capacity of 240.5 mAh g−1 at 1 A g−1. Direct sulfuration Ni(OH) 2 to obtain a single crystal NiS, control the sulfuration time to obtain porous Ni(OH) 2 /NiS composite electrode, and has excellent specific capacity and energy density. [Display omitted] [ABSTRACT FROM AUTHOR]