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The development of active and durable cathode materials is the key to achieving high-performance water-based zinc-ion batteries.

Among the electrode materials for supercapacitors (SCs), metal-organic framework (MOFs) is attracting huge research interest as a new type of energy storage electrode materia. However, due to their poor conductivity and stability, the practical application of original MOFs in the field of energy storage has been greatly hindered. Here, we demonstrate a special core-shell structure, which the synergistic action of NiCo2O4 and Ni-MOF forms a tight conductive network that speeds up electron transport and larger specific surface area, more active sites were obtained and mechanical stability that indicates its outstanding long life. The test results show that it has a high specific capacity of 4.23 F cm-2 at 5 mA cm-2, and the capacity retention rate is maintained at 97.5% after 8000 cycles. In addition, the assembled hybrid SCs device, using NiCo2O4@Ni-MOF and activated carbon (AC) as anode and cathode, has a high specific capacity of 3.21 F cm-2 at 5 mA cm-2 and excellent cycling performance (83.8% retention over 8000 cycles at 10 mA cm-2). Our work demonstrates the possibility of using novel structured Ni-MOF-based hybrid arrays as electrodes for SCs with enhanced electrochemical performance compared to Ni-MOF and NiCo2O4, providing a reliable prospect for flexible energy storage devices.

It is still challenging to develop suitable cathode structures for high-rate and stable aqueous Zn-ion batteries. Herein, a phosphating-assisted interfacial engineering strategy is designed for the controllable conversion of NiCo2S4 nanosheets into heterostructured NiCoP/NiCo2S4 as the cathodes in aqueous Zn-ion batteries. The multicomponent heterostructures with rich interfaces can not only improve the electrical conductivity but also enhance the diffusion pathways for Zn-ion storage. As expected, the NiCoP/NiCo2S4 electrode has high performance with a large specific capacity of 251.1 mA h g−1 at a high current density of 10 A g−1 and excellent rate capability (retaining about 76% even at 50 A g−1). Accordingly, the Zn-ion battery using NiCoP/NiCo2S4 as the cathode delivers a high specific capacity (265.1 mA h g−1 at 5A g−1), a long-term cycling stability (96.9% retention after 5000 cycles), and a competitive energy density (444.7 W h kg−1 at the power density of 8.4 kW kg−1). This work therefore provides a simple phosphating-assisted interfacial engineering strategy to construct heterostructured electrode materials with rich interfaces for the development of high-performance energy storage devices in the future.

Fe2O3 electrode materials exhibit excellent electrochemical performance in electrochemical energy storage system. However, its poor electrical conductivity limits its future practical application. The binder-free NiCo2O4@Fe2O3 composites was reasonably designed and fabricated on carbon fiber paper with NiCo2O4 nanowires as conductive scaffold in the present investigation. The three-dimensional nanostructure of the porous Fe2O3 nanorods coated the NiCo2O4 nanowire arrays showed the fascinating electrochemical performance, including high specific capacitance of 262 ​mF/cm2 at a current density of 1 ​mA/cm2, and remarkable cycle stability with ~74.2% capacitance retention after 4000 cycles. The excellent pseudocapacitance performance of NiCo2O4@Fe2O3 composite materials is due to synergistic effect between NiCo2O4 and Fe2O3. The results of the present work show that NiCo2O4@Fe2O3 core-shell composite electrode is expected to exhibit excellent performance in the field of supercapacitors.

Controlling the morphology and structure of nanomaterials is of great importance for enhancing the electrochemical properties. In the paper, Mn3O4-Fe3O4@C hybrids with different architectures were synthesized by incubation of electrospun FeOx-containing carbon fiber (Fe-CNF) in KMnO4 solution followed by annealing. The presence of FeOx on the CNF plays a vital role in determining the morphology and structure of the final hybrids, and the Mn3O4-Fe3O4@C hybrids with half-tube, tube and oolite-filled fibers are formed conveniently by tuning Fe content in the carbon fiber precursor. The good conductivity of fiber and various redox states of Mn and Fe afford the facile charge transfer and excellent reversible redox properties, thus enhancing the capacitor performance. The oolite-filled Mn3O4-Fe3O4@C with tubular structure exhibited a high specific capacitance of 178 F g−1 at a discharge rate of 1 A g−1. This capacitor electrode has an excellent cyclic stability with 95% capacitance retention after 1000 cycles at 3 A g−1. This work provides a very simple strategy to tune the unique nanostructures of metal oxide on Fe-CNF for high-performance supercapacitor application in the future.

Aqueous zinc-ion batteries (ZIBs) are emerging as promising alternatives among various energy storage devices. However, the lack of research on cathode materials with both high capacity and electrochemical stability restricts widespread applications of ZIBs. Herein, surface chemical reconstruction and partial phosphorization strategies are employed to synthesize MOF-derived hierarchical CoO/Ni2P-Co2P nanosheet arrays on Ni foam substrates as cathodes for ZIBs. The unique hierarchical nanostructure and multiple components with exposed surfaces and rich oxygen vacancies accelerate charge transfer and ion diffusion, expose more active sites, and promote the accessibility between the active materials and electrolyte. The oxide/phosphide composites obtained by novel partial phosphorization achieve a common improvement of performance and stability. As expected, the CoO/Ni2P-Co2P electrode delivers a high specific capacity (370.4 mA h g-1 at 3 A g-1) and excellent rate performance (63.3% retention after a six-fold increase in the current density). Moreover, when employed as the cathode of the CoO/Ni2P-Co2P-30//Zn battery, the assembled battery exhibits a superior specific capacity (322.8 mA h g-1 at 2 A g-1), a long cycle life (104.9% retention after 6000 cycles), a favorable energy density (547.5 W h kg-1) and power density (9.7 kW kg-1). Therefore, this study provides a suitable candidate which meets the requirements of high-performance cathode materials for ZIBs.

The enhancement of energy density and cycling stability is in urgent need for the widespread applications of aqueous rechargeable Ni-Zn batteries. Herein, a facile strategy has been employed to construct hierarchical Co-doped Ni-MoO4 nanosheets as the cathode for high-performance Ni-Zn battery. Benefiting from the merits of substantially improved electrical conductivity and increased concentration of oxygen vacancies, the NiMoO4 with 15% cobalt doping (denoted as CNMO-15) displays the best capacity of 361.4 mA h g−1 at a current density of 3 A g−1 and excellent cycle stability. Moreover, the assembled CNMO-15//Zn battery delivers a satisfactory specific capacity of 270.9 mA h g-1 at 2 A g−1 and a remarkable energy density of 474.1 W h kg−1 at 3.5 kW kg−1, together with a maximum power density of 10.3 kW kg−1 achieved at 118.8 W h kg−1. Noticeably, there is no capacity decay with a 119.8% retention observed after 5000 cycles, demonstrating its outstanding long lifespan. This work might provide valuable inspirations for the fabrication of high performance Ni Zn batteries with superior energy density and impressive stability.

Carbon materials doped with sulfur (S) and nitrogen (N) are prospective alternatives to Pt-based catalysts as oxygen reduction reaction (ORR) catalyst since they are inexpensive and highly catalytic active. However, the further advancement of catalysts is greatly hindered for its unclear and equivocal catalytic sites. Here, using density functional theory studies, we find that those inactive carbon atoms next to graphitic N become ORR catalytic sites after S doping, which is distinctly different from N-doped carbon materials where catalytic sites are introduced by pyridinic N. The electrochemical results show that increasing the content of graphitic N can lead to higher catalytic activity for S and N dual-doped carbon materials, which exhibits higher turnover frequency towards ORR than that of N-doped carbon materials. This work provides insights for further advancement of electrocatalysts via heteroatom doping.

Aqueous zinc-ion batteries (ZIBs) are emerging as promising alternatives among various energy storage devices. However, the lack of research on cathode materials with both high capacity and electrochemical stability restricts widespread applications of ZIBs. Herein, surface chemical reconstruction and partial phosphorization strategies are employed to synthesize MOF-derived hierarchical CoO/Ni

As one of the most reliable power sources for portable and wearable electronics, aqueous zinc-ion batteries fully meet the requirement of high safety, while their energy storage ability is still limited by the lack of high-performance cathode materials. In this study, the poor electrical conductivity and sluggish interface reaction of cobalt molybdate (CoMoO4) nanosheets are well addressed by one-step phosphating treatment (denoted as P-CoMoO4), which serve as an advanced cathode material for rechargeable zinc-ion batteries. Primarily, the electronic structures are finely manipulated using enriched oxygen vacancies, therefore improving the electronic conductivity and reaction activity. Moreover, the modification of surface phosphate ions can reduce the required activation energy for redox reactions and consequently increase the reaction kinetics. Additionally, abundant metallic CoP nanoparticles are uniformly distributed in the matrix of CoMoO4 nanosheets, boosting the exposure of active sites and interface reactions. As expected, the optimized P-CoMoO4 electrode shows a superior specific capacity (431.4 mA h g−1 at 10 A g−1) and rate performance (43.8% capacity retention at 50 A g−1) relative to pristine CoMoO4. Furthermore, the assembled P-CoMoO4//Zn battery exhibits a remarkable energy density of 679.4 W h kg−1 at 8.6 kW kg−1, and an ultra-long life span (over 80% retention of the initial capacity after 12 000 cycles at 60 mV s−1). Hence, this work may offer a preferable option for high-performance cathode materials for aqueous zinc-ion batteries.

A high-performance broadband photodetector based on a Zn-doped NiO/p-Si isotype heterojunction was successfully fabricated, which consisted of a Zn-doped NiO film on a Si substrate via a facile sol–gel method. The as-fabricated isotype heterojunction device displays an excellent broad-band (350–650 nm) detection performance with an outstanding external quantum efficiency (EQE) of 89.5% at a small reverse bias of −1 V and as high as ∼184% at −4 V. Moreover, the maximum photo–dark current ratio (switching ratio) of 1793% was achieved at −1 V under illumination with 650 nm light (0.5 mW cm−2); additionally, the response time of the as-fabricated device was less than 0.3 s. Such a high-performance of the Zn-doped NiO/p-Si isotype heterojunction photodetector guarantees its potential use in UV-visible low-voltage optoelectronic devices, especially for weak-signal detection and portable equipment.

The design of multicomponent electrode materials is attractive for advanced supercapacitors due to synergistic and multifunctional effects among different active materials. We reported here a structure-designed synthesis strategy to controllably fabricate hierarchical NiCo2O4@NiO composites on carbon fiber paper. The hierarchical structure with NiCo2O4 core and NiO shell provided more active sites for ion transportation and storage to improve utilization rate of electrode materials, enhancing the specific capacitance and rate performance. As an ideal electrode material for supercapacitors, the NiCo2O4@NiO electrode exhibit high specific capacitance (1188 F/g at 2 A/g), excellent rate capability with ∼85% capacitance retained at 10 A/g, and compelling cycling performance (∼106.8% of the initial capacitance retention over 7000 cycles). The present work demonstrated a structure-designed strategy to construct high-performance multicomponent electrode materials for supercapacitors.

Visible-light-driven (VLD) heterojunction photocatalysts for refractory contaminant degradation have aroused huge interest because of their outstanding photocatalytic performance. From the aspect of practical application, it is important to develop a highly efficient, durable, eco-friendly and inexpensive VLD photocatalyst. Herein, we report a novel VLD WO3/Bi2MoO6 heterojunction photocatalyst with remarkable photocatalytic activity, which was fabricated via an electrospinning–calcination–solvothermal route. The phase, composition, morphologies, and optical properties of WO3/Bi2MoO6 heterojunctions were comprehensively characterized. The photocatalytic performance of WO3/Bi2MoO6 heterojunctions was assessed by the removal of rhodamine (RhB) and tetracycline hydrochloride (TC) under visible light (VL). WO3/Bi2MoO6 heterojunctions displayed superior photocatalytic activities compared to Bi2MoO6, WO3, or the mechanical mixture of WO3 and Bi2MoO6. In particular, the heterojunction material (0.4WB, theoretical molar ratio of WO3/Bi2MoO6 is 0.4/1.0) exhibited the best degradation efficiency (100%) and mineralization rate (52.3%) in 90 min, both of which exceeded the observed rates for Bi2MoO6 by 5.3 and 6.4 times, respectively. Moreover, 0.4WB showed a good durability in eight runs. The optimized photocatalytic property of WO3/Bi2MoO6 can be attributed to enhanced VL absorption and reduced recombination efficiency of carriers owing to the synergistic effects between Bi2MoO6 and WO3. The necessity of direct contact between WO3/Bi2MoO6 and contaminants was experimentally verified. The study on photocatalytic mechanism demonstrates that superoxide free radicals (O2 −) and photo-generated hole (h+) are dominantly responsible for the pollutant degradation, as demonstrated by the trapping experiments and electron spin resonance (ESR) analysis. Therefore, the WO3/Bi2MoO6 heterojunction holds huge potential to be utilized as a durable and highly active photocatalyst for wastewater treatment.

Herein, we report the rational design and fabrication of multicomponent, hierarchical CuCo2O4 nanowire arrays wrapped with metal oxides (NiO, Co3O4 and MnO2) nanosheets for use in high-performance supercapacitors. Among all the composite electrodes prepared, the CuCo2O4@NiO electrode exhibits the best electrochemical behavior with a high areal capacitance of 2.3 F/cm2 at 2 mA/cm2 and excellent cycling stability. The asymmetric supercapacitor with CuCo2O4@NiO as the positive electrode shows a superior specific capacitance of 124.6 F/g at 1 A/g, exceptional energy density of 38.9 Wh/kg at 750 W/kg, and long cycle life with ∼81.3% capacitance retention after 6000 cycles. The results indicate that the CuCo2O4@NiO electrode shows great potential for high-performance electrochemical energy storage.

Conducting polymers and transition metal oxides are good electrodes for supercapacitors owing to their high charge storage characteristics. Different techniques have been utilized in fabricating novel nanocomposites of polyaniline (PANI) and manganese dioxide (MnO2) for capacitance enhancement. Herein, we report a facile approach towards the control of core/shell architecture of MnO2 nanorods and PANI, respectively, via in-situ hydrothermal polymerization method. Structure and morphology of the PANI wrapped MnO2 nanorods (MnO2@PANI) were properly characterized and their capacitance enhancement was explored carefully. The experimental results revealed that the specific capacitance of MnO2@PANI40 (40% MnO2 relative to aniline monomer) nanocomposite is 665 F g-1 at a current density of 1 A g-1, higher than that of pristine MnO2 (273 F g-1) and pristine PANI (434 F g-1). Moreover, 82% of the original capacitance of the nanocomposite is retained after 1500 consecutive CV cycles at a scan rate of 100 mVs−1, which is far higher than the stability of pristine PANI (48%). Excellent electrochemical performance of the MnO2@PANI40-based electrode is attributed to the synergistic effect of the core/shell networked hierarchical structure of the nanocomposite. The unique structure improves the ion transportation efficiency and reduces the ion diffusion path and the uniform coating of PANI offers protection against the dissolution of MnO2 in the acidic electrolyte. Furthermore, high electrical conductivity status of PANI (due to its half oxidation-half reduction status, justified by XPS test) plays an important role in the capacitance enhancement of the nanocomposite.

Developing hybrid materials with hierarchical combination of different active materials is of great importance to improve its whole electrochemical performance. This study reports a facial approach to fabricate Co3O4@NiMoO4 composites on Ni foam as an efficient supercapacitor electrode. The synthesized Co3O4@NiMoO4 composites show high areal capacitance of 3.61 F/cm2 at a current density of 2 mA/cm2. And ∼101.3% of its initial capacitance was still retained after 9000 cycles. The outstanding electrochemical properties are attributed to the uniquely hierarchical nanostructure and the components' synergetic effect, showing great potential for energy storage applications.

The poor charge separation of single-component semiconductor photocatalysts greatly restrains their practical application. Herein, we report an in situ anion-exchange strategy to controllably fabricate sunlight-driven p-n heterostructure photocatalyst BiOCl/BiOCOOH. In this synthetic process, the BiOCOOH microspheres not only act as the support to form heterostructures but also as Bi3+ supplier to generate BiOCl. Such an in situ anion-exchange route thus brought about the homogeneous distribution of BiOCl on the surface of BiOCOOH with tight interfacial contact. Under simulated solar illumination, the obtained BiOCl/BiOCOOH catalysts with p-n heterostructures show exceedingly superior photocatalytic activity against toxic pollutant (MO dye and TC antibiotic) to BiOCOOH and BiOCl. The optimal BiOCl/BiOCOOH, S3 sample has the highest photocatalytic activity with MO degradation rate constant of 0.0599 min−1, 2.9 or 9.7 folds higher than that of BiOCOOH or BiOCl. The alleviated charge separation and transfer as well as the flower-like structure mainly account for the enhanced performance. Radical scavenging experiments indicate that holes, OH and O2− collaboratively contribute to the degradation of pollutants. This work provides a novel sunlight-driven p-n heterojunction photocatalyst of BiOCl/BiOCOOH for wastewater treatment.

Organic materials are receiving more attention in the solar cell due to their better solution process, controllable synthesis, tunable chemical and physical properties. However, the focus problem of compatibility and aggregation is to be solved urgently in organic materials, which inevitably limits them widely application. To this end, an inorganic–organic hybrid materials with wide-band absorption is designed and prepared, that incorporates octavinyl-polyhedral oligomeric silsesquioxane with 6-bromoquanaldine to produce H1, then reacts with squaric acid to design H2, which efficiently avoids the fluorescence quenching due to the steric hindrance. The electrochemical results shows that the energy level of H2 is match well with the commercial dye N719. Hence it shows a better photovoltaic performance based on dye-sensitized solar cell, along with power conversion efficiency up to 7.73% when it is co-sensitized with N719. The hybrid system exhibits good performances in solar cell and long-term stability.

The metal ion fluorescence probes based on chemical reactions triggered by specific metal ions is characterized by high selectivity. However, they are also subject to inherent limitations, such as easy aggregation under water solution, poor optical stability, and long response time. In order to solve these problems, a simple and effective method was studied. The specific design is as follows. Fluorescence probe RACD is assembled onto a single layer graphene oxide (GO) via π-π interaction and hydrogen bonding to prepare RACD functionlized graphene oxide RACD/GO. The experimental results show that the resulting RACD/GO possesses very well monodispersion, hydrophilicity and photostability, particularly reduce the aggregation degree of RACD owing to π-π effect. Simultaneously, it was found that due to the strong synergy between GO and RACD, the response time, selectivity, anti-interference ability, detection sensitivity, detection limit and bioimaging ability of RACD/GO were significantly improved compared with RACD. The resulting RACD/GO not only possesses very well photostability, multiple repeated cycles, but also have been triumphantly put into the monitoring Cu

Interface engineering multi-component core-shell nanostructures with highly efficient and reversible faradaic reactions for energy conversion storage devices is still a challenge. Here, Co

Controlling the morphology and structure of nanomaterials is of great importance for enhancing the electrochemical properties. In the paper, Mn

The ginkgo leaf-derived graphitic-N-doped porous carbon was fabricated by one-step carbonization in the presence of KOH agent. The morphology, surface functional groups, element state and porous structure of the obtained carbon were investigated systematically. Compared with the carbon samples by ginkgo-leaf carbonization and KOH post-activation (two-step), the one-step activated porous carbon exhibits high graphitic-N content and good electric conductivity. The conductive-agent-free carbon sheet was made successfully and the resultant carbon electrode possesses good conductivity and excellent electrochemical properties, with the specific capacitance of 176.1 F g−1. When being applied for capacitive deionization, the desalination amount of the electrode arrived at 16.5 mg g−1. Meanwhile, the salt adsorption rate is very rapid, with the average salt adsorption rate reaching 1.5 mg g−1 min−1. This work provides an easy and environmentally benign route for the synthesis of the conductive carbon from natural raw materials for highly efficient capacitive deionization.

In this work, three-dimensional (3D) TiO₂ nanotubes (NTs) on carbon cloth (CC) (TiO₂ NTs/CC) were synthesized by a method involving formation of a ZnO@TiO₂ nanorod (NRs) on CC (ZnO@TiO₂ NRs/CC) structure and a subsequent chemical etching process for ZnO NRs template. The 3D TiO₂ NTs/CC were applied as flexible anodes for sodium ion batteries (SIBs). The TiO₂ NTs/CC yielded high specific capacity and good cycling stability, superior to that of some reported TiO₂ nanocomposites. The TiO₂ NTs/CC delivered a reversible capacity of 260 mA·h·g-1 and 85.1% capacity retention over 150 cycles at current density of 0.25 C (1 C = 335 mA·g-1). It also exhibited high rate capacity of 200 mA·h·g-1 at 0.5 C. Even at a high rate of 1.0 C, the TiO₂ NTs/CC can still maintain a high capacity of 100 mA·h·g-1. Moreover, it was observed that the electrochemical performance for the TiO₂ NTs/CC was much better than that (150 mA·h·g-1 for up to 150 cycles) of a solid TiO₂ NRs/CC counterpart, which also demonstrated the capacity enhancement and good cycling stability.

Crystal engineering of CH3NH3PbI3–xClx perovskite films through modification by decoration with p-type semiconductor materials was proposed as an efficient method for obtaining good-quality crystalline films. A simple method is demonstrated to improve the quality of perovskite films by adding nickel oxide (NiOx) nanoparticles into the precursor solution. The addition of NiOx brings about high-quality crystals and convenient photo-generated charge transport with reduced defect density owing to efficient control of the preferred nucleation and crystal growth. The sufficient contact between CH3NH3PbI3–xClx–NiOx and the electron-transport layer can contribute to photo-generated carrier lifetime and transport through the optimized interface. Moreover, it is demonstrated that a strong chemical bonding interaction between MAPbI3–xClx and NiOx could protect perovskite materials from oxygen and humidity corrosion, showing remarkable stability holding ∼81% of the initial power conversion efficiency (PCE) after 50 d...

One dimensional (1D) hollow nanostructures have been considered as one of the most fascinating materials for supercapacitors. Herein, the hollow MnO2 nanofibers are successfully synthesized through a two-step process, in which the electrospun carbon nanofibers acted as sacrificial template. The resulting hollow nanofibers are composed of ultrathin MnO2 nanosheets, which can offer rich electrochemical active sites for electrochemical reactions. Importantly, the open and free interspaces among these ultrathin MnO2 nanosheets can significantly enhance the utilization of the active material even at high current density. Such unique hollow nanostructure endow the hollow MnO2 nanofibers electrode better electrochemical performance with specific capacitance of 291 F/g at 1 A/g, superior rate capability of ∼73% (from 1 to 10 A/g), and excellent cycling stability of 90.9% retention after 5000 cycles, demonstrating the potential for practical application in energy storage devices.

A nitrogen-doped carbon bubble-carbon nanotube@red phosphorus (N-CBCNT@rP) network composite is fabricated, featuring an rP film embedded in a highly N-doped CBCNT network with hierarchical pores of different sizes and interior void spaces. Highly N-doped CBCNT with an optimized structure is utilized to achieve an ultrahigh rP content of 53 wt% in the N-CBCNT@rP composite by the NP bond, which shows a record rP content for rP-carbon composites by the vaporization-condensation process. When tested as an anode for lithium-ion batteries, the N-CBCNT@rP composite exhibits an ultrahigh initial Coulombic efficiency of 87.5%, high specific capacity, outstanding rate performance, and superior cycling stability at a high current density (capacity decay of 0.011% per cycle over 1500 cycles at 5 A g

Hollow micro-/nanostructured electrode materials with high active surface area are highly desirable for achieving outstanding electrochemical properties. Herein, we report the successful synthesis of hierarchical hollow NiCo2O4 nanospheres with high surface area as electrode materials for supercapacitors. Electrochemical measurements prove that such electrode materials exhibit excellent electrochemical behavior with a specific capacitance reaching 1229 F/g at 1 A/g, remarkable rate performance (∼83.6% retention from 1 to 25 A/g) and good cycling performance (86.3% after 3000 cycles). Furthermore, the asymmetric supercapacitor is fabricated with hollow NiCo2O4 nanospheres electrode and activated carbon (AC) electrode as the positive and negative, respectively. This device exhibits a maximum energy density of 21.5 W h/kg, excellent cycling performance and coulombic efficiency. The results show that hollow NiCo2O4 nanosphere electrode is a promising electrode material for the future application in high performance supercapacitors.

Herein, a novel hybrid S@MnO2@C nanosphere, comprising sulfur nanoparticles encapsulated by a MnO2@C hollow dual-shell, is reported. Benefiting from a conductive C outer layer, the S@MnO2@C hybrid nanosphere provided highly efficient pathways for fast electron/ion transfer and sufficient free space for the expansion of the encapsulated sulfur nanoparticles. Moreover, the dual-shell composed of a MnO2 inner layer and a C outer layer coating on S not only improved the efficacious encapsulation of sulfur, but also significantly suppressed the dissolution of polysulfides during cycling. As a result, the S@MnO2@C electrode shows high capacity, high coulombic efficiency and excellent cycling stability. The S@MnO2@C cathode delivered a discharge capacity of 593 mA h g−1 in the fourth cycle and was able to maintain 573 mA h g−1 after 100 charge–discharge cycles at 1.0C, corresponding to a capacity retention of 96.6%.

Here, a surface phosphating Co3O4 electrode materials with multidimensional nanostructure and oxygen-deficient have been fabricated and applied to aqueous Zn-ion batteries and asymmetric supercapacitors. The multidimensional nanostructure is beneficial to the full contact between active materials and electrolyte. Moreover, the oxygen vacancies can enhance electrical conductivity and further increases the concentration of active sites, consequently accelerating their interface reaction activity and kinetics. Therefore, the combination of structural and compositional advantages endows the P-Co3O4 nanosheets/nanowires electrode a specific capacity of 244.9 mAh g−1 at 4 A g−1. Furthermore, the assembled P-Co3O4//Zn battery showed fascinating electrochemical performance, including a high specific capacity of 119.4 mAh g−1 at 1 A g−1 and a high energy density of 193.7 Wh kg−1 at a power density of 1.6 kW kg−1 and excellent stability of 111% capacity retention after 5000 cycles. The assembled P-Co3O4//AC ASC device also achieved an energy density of 24.87 Wh kg−1 and excellent cycle stability. Outstanding performance advantages make it possible for P-Co3O4 electrode to be applied in the fields of new energy storage devices and wearable electronic devices.

Herein we demonstrate the rational design and fabricate of the Co3O4 nanowire@Fe2O3 nanorod core-shell nanowire arrays on carbon cloth for supercapacitor electrodes. When measured as electrode material for supercapacitors, the Co3O4@Fe2O3 electrode delivers high areal capacitance of 245 mF/cm2 at a current density of 1 mA/cm2. The excellent electrochemical performances of the Co3O4@Fe2O3 electrode can be attributed to the unique core-shell nanoarchitecture and synergistic effect. The hydrothermally synthesized Co3O4 nanowire arrays serve as the conductive scaffold for the growth of mesoporous Fe2O3 nanorods, which facilitate fast charge transport throughout the whole electrode. These results indicate that the Co3O4@Fe2O3 core-shell nanowire arrays are a promising electrode material for next-generation high-performance supercapacitors.

Hierarchical MoO 3 /MnO 2 core-shell nanostructures were prepared by a hydrothermal process followed by in-situ oxidative polymerization as an integrated electrode material for supercapacitors. The core-shell MoO 3 /MnO 2 nanocomposites exhibited excellent electrochemical properties with high specific capacitance of 352.4 F g −1 at 1 A g −1 and desirable rate capability in 1 M NaOH solution. The superior electrochemical performances could be ascribed to the MoO 3 /MnO 2 core-shell nanostructures which make two types of pseudocapacitive materials connected physically and significantly improve electrolyte diffusion efficiency and electron transport. These MoO 3 /MnO 2 core-shell nanostructures with remarkable electrochemical performances could be considered as a prospective candidate for the application of supercapacitors.

In this work, plasmonic Ag nanoparticles (NPs) decorated BiOCOOH microflowers as one kind of efficient visible-light-driven photocatalysts were prepared via a one-pot solvothermal method and systematically characterized. Compared with pristine BiOCOOH, Ag/BiOCOOH heterojunctions showed greatly enhanced visible light photocatalytic activities towards RhB degradation. Especially, the 5 wt% Ag/BiOCOOH heterojunction displayed the maximum activity, and the degradation rate is 10.9 times higher than that obtained by using pristine BiOCOOH. The exceptional photocatalytic activity of Ag/BiOCOOH is attributed to the surface plasmon resonance (SPR) effect induced by Ag NPs and formation of the heterojunction between Ag and BiOCOOH. Holes and superoxide radicals mainly dominate the RhB degradation. More importantly, Ag/BiOCOOH is highly stable in photocatalysis.

Construction of core-shell heterostructures with multifunctionalities has been regarded as promising materials to improve the supercapacitor performances for single metal oxide. In our work, hierarchical Co 3 O 4 @NiCo 2 O 4 core-shell nanosheets are successfully fabricated on Ni foam for supercapacitors. The Co 3 O 4 @NiCo 2 O 4 electrode demonstrates excellent supercapacitor performances with the areal capacitance of 1.33 F/cm 2 at 3 mA/cm 2 , the specific capacitance of 1330 F/g at 3 mA/cm 2 and superior cycling stability of ∼100.7% after 5000 cycles. The excellent electrochemical properties for the Co 3 O 4 @NiCo 2 O 4 hybrid composites can be ascribed to the unique core-shell nanostructures as well as the synergistic effect of Co 3 O 4 and NiCo 2 O 4 . The as-prepared Co 3 O 4 @NiCo 2 O 4 hybrid composites with enhanced performances could be considered as a promising electrode material for high-performance supercapacitors.

Three-dimensional Ni x Co 3−x S 4 @NiCo 2 O 4 (x = 1.8) hybrid nanostructures supported on Ni foam was designed and fabricated for supercapacitor. Among different Ni-Co stoichiometries of Ni x Co 3−x S 4 electrode materials studied, Ni x Co 3−x S 4 (x = 1.8) electrode materials showed the highest capacitance of 1.908 F/cm 2 . Moreover, the smart combination of Ni x Co 3−x S 4 (x = 1.8) and NiCo 2 O 4 electrode materials exhibited strong synergistic effect with significantly enhanced performances of areal capacitance up to 4.44 F/cm 2 .

MWCNTs/BiOCOOH composites comprised of BiOCOOH nanosheets and MWCNTs were prepared by a facile solvothermal method. Photocatalytic properties of all catalysts were assessed by degrading RhB and 4-CP under simulated sunlight irradiation. The MWCNTs/BiOCOOH composites were much more active than BiOCOOH, and a mechanical mixture of MWCNTs and BiOCOOH. Especially, the MWCNTs/BiOCOOH composite with 3 wt% MWCNTs (3%M-B) presented the highest activity. The high photocatalytic activity was due to the effective electron-hole separation and improved visible-light harvesting. Trapping experiments revealed that the holes and superoxide radicals were the primary active species for the RhB degradation. Moreover, it also displayed good stability.

The development of efficient semiconductor heterojunction photocatalysts has drawn much attention. Herein, we have reported a kind of flower-like Ag 2 O/BiOCOOH p - n heterojunction as a novel and efficient visible-light-driven photocatalyst. The Ag 2 O/BiOCOOH heterojunctions have been successfully prepared via a solvothermal precipitation-deposition method. They consist of flower-like BiOCOOH microspheres (diameters: 1–2.5 μm) decorated with Ag 2 O nanoparticles (size: ∼14 nm). In addition, optical characterization reveals that they have broad visible-light photo-absorption. Importantly, under visible-light irradiation (λ > 400 nm), all Ag 2 O/BiOCOOH heterojunctions exhibit enhanced photocatalytic activity than pure BiOCOOH or Ag 2 O for the degradation of rhodamine B (RhB) dye and para -chlorophenol (4-CP). Especially, the Ag 2 O/BiOCOOH heterojunction with the Ag/Bi molar ratio of 0.2/1 shows the highest photocatalytic activity, which is even higher than the activity from the mechanical mixture (8 wt% Ag 2 O + 92 wt% BiOCOOH). This enhanced photocatalytic performance could be predominantly attributed to the efficient separation of photogenerated electron-hole pairs. The photogenerated holes (h + ) and superoxide radical anions ( O 2 − ) have been found to be the main reactive species responsible for the photodegradation of RhB dye in aqueous solution. Therefore, the Ag 2 O/BiOCOOH p - n heterojunction has great potential to be used as a kind of efficient visible-light-driven photocatalyst.

The development of nickel cobalt sulfides electrodes with excellent electrochemical performance is important for supercapacitor applications. In this study, we constructed well-defined hierarchical nanosheet-built NiCo2S4/Co9S8 hollow nanospheres based on morphology and structural engineering. A combination of structural and compositional advantages endowed NiCo2S4/Co9S8 hollow nanospheres with enhanced electrochemical performance with favorable capacitance of 1008 F g−1 at 1 A g−1, exceeding that of single-component NiS (616 F g−1 at 1 A g−1) and Co3S4 (430 F g−1 at 1 A g−1). Furthermore, an assembled asymmetric supercapacitor (ASC) comprising NiCo2S4/Co9S8 hollow nanospheres and activated carbon achieved a high energy density up to 36.7 Wh kg−1 at 800 W kg−1, suggesting that it could be a promising electroactive material for energy storage devices.

MnO2 has attracted considerable attention for use in supercapacitors. Nevertheless, its low electrical conductivity greatly hinders its potential application. Here, we demonstrate the fabrication of a high-performance electrode material via facile coating of hierarchical MnO2 nanosheets onto highly electrically conductive one-dimensional (1D) TiN nanofibers for use in supercapacitors. The TiN nanofibers are prepared through nitridation electrospinning of TiO2 nanofibers via ammonia annealing. The obtained TiN@MnO2 composites exhibit enhanced electrochemical properties, such as high specific capacitance of 386 F/g at a current density of 1 A/g, and long cycle stability of ∼111.7% capacity retention after 4000 cycles at 6 A/g. The unique nanostructure and significant synergistic effect between TiN and MnO2 are responsible for its good electrochemical performance.

In this work, the preparation of a single-layer nanocomposite electrode material with good electron transfer through controlled assembly was studied, and it was used for high-sensitivity electrochemical detection of Pb2+. Mechanism studies have found that single-layer graphene nanostructures bring significant advantages to electron transfer along RhB/RGO nanocomposite electrode material. This solving the main obstacle of low electron transfer caused by aggregation in electroanalysis. Moreover, since RhB has good metal ion adsorption capacity, it helps to enhance the interfacial adhesion between graphene and target metal ions. Through the synergistic enhancement of RhB and RGO, RhB/RGO shows high sensitivity in Pb2+ trace analysis. The detection limit is 10 nM, and the linear correlation coefficient is 0.9999. RhB/RGO/GCE sensors have been used to detect Pb2+ in environmental water. In addition, the competitive relationship between the active binding site and the electron transfer resistance (Rct) in the detection of Pb2+ was studied. This provides a reference for the design of electrode materials in the future.

The metal ion fluorescence probes based on chemical reactions triggered by specific metal ions is characterized by high selectivity. However, they are also subject to inherent limitations, such as easy aggregation under water solution, poor optical stability, and long response time. In order to solve these problems, a simple and effective method was studied. The specific design is as follows. Fluorescence probe RACD is assembled onto a single layer graphene oxide (GO) via π-π interaction and hydrogen bonding to prepare RACD functionlized graphene oxide RACD/GO. The experimental results show that the resulting RACD/GO possesses very well monodispersion, hydrophilicity and photostability, particularly reduce the aggregation degree of RACD owing to π-π effect. Simultaneously, it was found that due to the strong synergy between GO and RACD, the response time, selectivity, anti-interference ability, detection sensitivity, detection limit and bioimaging ability of RACD/GO were significantly improved compared with RACD. The resulting RACD/GO not only possesses very well photostability, multiple repeated cycles, but also have been triumphantly put into the monitoring Cu2+ of environmental water, sewage, cells and zebrafish specimens in practice. The detection limit is as low as 1.76 nM, and the correlation coefficient is 0.9998.

Birnessite-type MnO2 (δ-MnO2) nanosheet assembly with various structures were achieved by redox reaction of KMnO4 under acidic condition with Fe regulation on Fe-doping carbon nanofibers (Fe-CNFs). The Fe-CNFs with various Fe contents were conveniently obtained by carbonization of the electrospun ferric acetylacetonate-polyacrylonitrile (AAI-PAN) fiber with various AAI ratios. X-ray diffraction and transmission electron microscopy demonstrated the formation of δ-MnO2 on the Fe-CNFs. pHs of KMnO4 solution and Fe content in the fiber affected the morphology of δ-MnO2. At pH = 2, the uniform δ-MnO2 nanosheet assembly was transferred into a tubular structure by adjusting Fe content in the Fe-CNFs template (AAI = 5%, mass ratio). The obtained δ-MnO2@Fe-CNF-5% exhibited the highest aspect ratio, large surface area and best charge-transfer behavior. The δ-MnO2@Fe-CNF-5% electrode delivered a specific capacitance of 210 F/g (0.3 A/g) and a superior cycling stability with 94% capacitance retention in 4500 cycles. The δ-MnO2@Fe-CNF-5%, as a negative electrode presented an excellent performance both in supercapacitor with high energy density (20 Wh/kg) and in capacitive deionization cell with the salt adsorption capacity of 20 mg/g. The unique nanostructure and excellent electrochemical performance render the δ-MnO2@Fe-CNF-5% composite as a much promising material for charge storage and deionization applications.

CuCo2O4 maguey-like nanowires were obtained via a facile hydrothermal reaction and subsequent annealing at 300 °C for 3 h. The CuCo2O4 nanowires interacting with each other to form CuCo2O4 maguey-like nanowires structure offers the great specific surface area, excellent electron and ion transfer ability, easy approach for electrolyte transmitting to electrode surface. Our prepared CuCo2O4 electrode materials showed a high areal capacitance of 3.27 F cm−2 at 5 mA cm−2, an outstanding specific capacitance of 982 F g−1 at 1.5 A g−1 and an excellent capacitance retention of 100.94% after 3000 circles at 50 mV s−1. In addition, a symmetry supercapacitor was been assembled with a high energy density of 16.87 Wh kg−1, a high power density of 8.2 kW kg−1 and outstanding cycle life, which demonstrates that our prepared material has great potential application for supercapacitors.

Ag2O/Fe2O3 p-n heterojunctions composed of flower-like Fe2O3 and Ag2O nanoparticles have been prepared via a solvothermal precipitation-deposition method. They display higher photocatalytic activities than pure Fe2O3 for the degradation of RhB under visible-light irradiation. Among them, the Ag2O/Fe2O3 heterojunction with the Ag/Fe molar ratio of 0.2/1 (0.2Ag-Fe) exhibits the highest activity and good stability. It was even more active than the mechanical mixture (22.5 wt% Ag2O +77.5 wt% Fe2O3). The superior photocatalytic activity of Ag2O/Fe2O3 heterojunction can be ascribed to p-n heterojunction between Ag2O and Fe2O3, facilitating the efficient separation of photogenerated charge carriers. The photogenerated holes and superoxide radical anions mainly account for the RhB degradation.

Ta 3 N 5 -Au heterojunction was prepared via a facile solvothermal precipitation-nitridation-wet impregnation method. Ta 3 N 5 -Au consisted of Ta 3 N 5 microspheres (diameters: 1–2.5 μm) and Au nanoparticles (size: ∼3.5 nm). Ta 3 N 5 microsphere was composed of nanorods (diameter: 20–30 nm; length: 400–500 nm), and Au nanoparticles were well-dispersed on the surface of Ta 3 N 5 nanorods. Photocatalytic performances of as-prepared catalysts were evaluated by the degradation of MB, RhB or 4-CP under visible light irradiation (λ > 400 nm), flower-like Ta 3 N 5 -Au exhibited higher photocatalytic activity than flower-like Ta 3 N 5 , bulk Ta 3 N 5 or Ta 3 N 5 -Au. The enhanced photocatalytic activity of Ta 3 N 5 -Au could be attributed to the synergistic effect of high surface area and efficient separation of photogenerated charge carriers. The photogenerated holes (h + ) and superoxide radical anions ( O 2 − ) were found to be the leading active species responsible for the degradation of RhB dye. The cycling experiments demonstrated that flower-like Ta 3 N 5 -Au had good recyclability.