Reasonable design and optimization of photocatalyst structure is an important strategy to realize sustainable hydrogen production. The rational design and interfacial tuning of Z-scheme heterojunctions remain challenging. Herein, a series of hollow cage-like Zn0.01Co0.99Se2/ZnIn2S4 Z-scheme heterojunction photocatalysts templated by cobalt-based bimetallic organic frameworks is successfully obtained via a hydrothermal approach. As expected, the optimized catalysts exhibit excellent hydrogen production performance without noble metal co-catalysts, which is mainly attributable to the synergistic effect of abundant active sites, strong light trapping and effective charge separation. Spectroscopic characterization and density functional theory (DFT) calculations indicate that the doping of Zn ions leading to more photogenerated carriers and faster charge transfer rates inside the heterojunction is another key factor in improving the catalytic performance. This work provides a feasible strategy for the optimization and design of Z-scheme heterojunctions through structural and interfacial engineering.

Heterojunctions coupled into micro-mesoscopic structures is an attractive strategy to optimize the light harvesting and carrier separation of semiconductor photocatalysts. A self-templating method of ion exchange is reported to synthesize an exquisite hollow cage-structured Ag2 S@CdS/ZnS that direct Z-scheme heterojunction photocatalyst. On the ultrathin shell of the cage, Ag2 S, CdS, and ZnS with Zn-vacancies (VZn ) are arranged sequentially from outside to inside. Among them, the photogenerated electrons are excited by ZnS to the VZn energy level and then recombine with the photogenerated holes that are generated by CdS, while the electrons remained in the CdS conduction band are further transferred to Ag2 S. The ingenious cooperation of the Z-scheme heterojunction with the hollow structure optimizes the photogenerated charges transport channel, spatially separated the oxidation and reduction half-reactions, decreases the charge recombination probability, and simultaneously improves the light harvesting efficiency. As a result, the photocatalytic hydrogen evolution activity of the optimal sample is 136.6 and 17.3 times higher than that of cage-like ZnS with VZn and CdS by, respectively. This unique strategy demonstrates the tremendous potential of the incorporation of heterojunction construction to morphology design of photocatalytic materials, and also provided a reasonable route for designing other efficient synergistic photocatalytic reactions.

Inspired by the unique properties of the three-dimensional hollow nanostructures in the field of photocatalysis, as well as the combination of co-catalyst, porous hollow spherical Pd/CdS/NiS photocatalysts are prepared by stepwise synthesis. The results show that the Schottky junction between Pd and CdS accelerates the transport of photogenerated electrons, while a p-n junction between NiS and CdS traps the photogenerated holes. As co-catalysts, the Pd nanoparticles and the NiS are loaded inside and outside the hollow CdS shell layer, respectively, which combines with the particular characteristic of the hollow structure, resulting in a spatial carrier separation effect. Under the synergy of the dual co-catalyst loading and hollow structure, the Pd/CdS/NiS has favorable stability. Its H2 production under visible light is significantly increased to 3804.6 μmol/g/h, representing 33.4 times more than that of pure CdS. The apparent quantum efficiency is 0.24% at 420 nm. A feasible bridge for the development of efficient photocatalysts is offered by this work.

Graphene and graphene-based materials have the ability to induce stem cells to differentiate into neurons, which is necessary to overcome the current problems faced in the clinical treatment of spinal cord injury. This review summarizes the advantages of graphene and graphene-based materials (in particular, composite materials) in axonal repair after spinal cord injury. These materials have good histocompatibility, and mechanical and adsorption properties that can be targeted to improve the environment of axonal regeneration. They also have good conductivity, which allows them to make full use of electrical nerve signal stimulation in spinal cord tissue to promote axonal regeneration. Furthermore, they can be used as carriers of seed cells, trophic factors, and drugs in nerve tissue engineering scaffolds to provide a basis for constructing a local microenvironment after spinal cord injury. However, to achieve clinical adoption of graphene and graphene-based materials for the repair of spinal cord injury, further research is needed to reduce their toxicity.

Designing a highly sensitive, fast response, cheap, and flexible biosensing platform has important significance in the diagnosis of diabetes. Herein, we developed an ultra-fast and sensitive glucose sensor based on CuO nanoflowers-coated stereo-graphene electrode on carbon cloth. The three-dimensional graphene (3DG) nanostructures were established on the carbon cloth (CC) by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD), and CuO nanoflowers subsequently obtained via chemical deposition. The prepared CuO@3DG@CC electrode with self-assembled structures provided abundant ion diffusion channels, large specific surface area and high conductivity, which shows an ultrasensitive current response to glucose. The detection limit of the sensor is as low as 0.068 mu M and the response efficiency is as fast as 0.5 s. The electrode has two linear ranges with 0.5-115.5 mu M and 165.5-1165.5 mu M and has a strong anti-interference ability and shows an excellent stability. This kind of flexible enzyme-free glucose sensor has been successfully applied to the detection of glucose in actual serum samples and shows a good accuracy, which is likely be applied to the medical testing field and the commercial production and has potential to further applied in wearable sensors.

In this work, we report a high-performance self-standing supercapacitor electrode of mixed nickel manganese sulfides (NMSs) with a cracked-bark shape grown by one-step electrochemical deposition on activated carbon cloth (ACC). The electrode possesses outstanding electrochemical properties, including a high specific capacitance of up to 3142.8 F g−1 at 1.0 A g−1, the high-rate performance (∼ 1206.8 F g−1 at 60.0 A g−1), and cycle stability (∼ 92.3% capacitance retention after 8000 cycles at 8 A g−1). An asymmetric supercapacitor assembled using NMSs on ACC as the cathode, activated carbon on carbon cloth as the anode and 1.0 mol L−1 KOH as the electrolyte delivers a high energy density of 111.2 W h kg−1 at 800.0 W kg−1 and the prominent cycling performance of ∼ 93.2% capacitance retention after 10000 cycles at 5 A g−1 with the Columbic efficiency of around 100% during these 10000 cycles. The high performance and facile preparation indicate that the NMSs on ACC hold a huge potential as the electrode for supercapacitors.

In this paper, we report a high-performance self-supported supercapacitor electrode composed of a cracked bark-shaped Ni-Co-Mn ternary metallic sulfide (NiCoMnS4) nanostructure on carbon cloth prepared by a simple one-step hydrothermal process and subsequent electrochemical treatment. The electrode delivers a high specific discharge capacity of up to 2470.4 F g−1 at 1 A g−1 and high rate performances of 1635.6 F g−1 at 10 A g−1 and 910.2 F g−1 even at 32 A g−1. Cycling tests indicate that NiCoMnS4 could maintain >91.1% of its initial capacity and nearly 100% Coulombic efficiency over 10,000 cycles at 8 A g−1. An aqueous asymmetric supercapacitor assembled with NiCoMnS4 as the cathode, activated carbon as the anode, and 1 mol L−1 KOH as the electrolyte delivers an energy density of 68.2 W h kg−1 at 850.1 W kg−1 and capacity retention of 92.5% after 10,000 cycles at 4 A g−1. Given the excellent performance and simple material preparation of our proposed device, this study provides a valuable foundation for the development of self-supported metallic sulfide based electrodes with high electrochemical properties for potential application in aqueous asymmetric supercapacitors.

In this paper, we report a self-supported flexible electrode consisting of NiCoMnS4 nanosheets on NiCo2O4 nanowires, denoted as NiCo2O4@NiCoMnS4 (NCO@NCMS) prepared by the hydrothermal growth (NiCo2O4) and the following electrodeposition (NiCoMnS4) on a carbon cloth (CC) substrate. The electrode delivers a high specific capacity of 4836 mF cm(-2) at 1 mA cm(-2) and excellent rate performance, i.e., 3820 mF cm(-2) at 10 mA cm(-2) and 2820 mF cm(-2) even at 60 mA cm(-2). An aqueous asymmetric supercapacitor (AASC) assembled using NCO@NCMS on CC as the cathode, activated carbon on CC as the anode and 2 M KOH as the electrolyte delivers a high energy density of 0.399 mWh cm(-2) at 0.85 mW cm(-2) and excellent cycle stability with similar to 81.2% capacity retention after 20 0 0 0 cycles at a high current density of 20 mA cm(-2). In view of the excellent performance and facile preparation, this study is believed to provide a valuable exploration of developing high-performance electrodes and AASCs. (C) 2021 Elsevier Ltd. All rights reserved.

Among various supercapacitor materials, transition metal oxides have attracted wide attention due to their high theoretical capacitance, and however a great challenge associated with the related materials is to fabricate nanostructured electrodes with high comprehensive performance including high capacitance, excellent cycle stability and good rate performance by a simple and green method. Herein, a high-performance self-supporting cathode consisting of interconnected delta-MnO2 nanosheets on graphite paper (GP) is developed by water bath only at 40 degrees C. Benefiting from the synergetic effects from the interconnected and open nanosheet structure of delta-MnO2 and the GP substrate including effective contact with the electrolyte, a large specific surface area, efficient stress relief, improved ion diffusion and charge transfer, and small equivalent series resistance, a high specific capacitance of 446.6 F g(-1) at 1 A g(-1), 1.3 V potential window, and outstanding cycle stability with the capacitance retention of similar to 86.1% after 10000 cycles at 8 A g(-1) and Columbic efficiency around 100% during cycling can be achieved for the cathodes. The aqueous asymmetric supercapacitors assembled using the delta-MnO2 cathode and active carbon anode and 1 M NaNO3 aqueous solution electrolyte can deliver a specific energy of 47.2 and 19.8 W h kg(-1) at 1150 and 115000 W kg(-1), respectively. Moreover, long cycle stability with 87.2% capacitance retention even after 30000 cycles at 4 A g(-1) can be maintained by the ASCs. Thanks to the simple and green preparation and high performance of the electrodes, valuable exploration of developing high-performance ASCs can be provided by this work.

The potential window for aqueous supercapacitor cathodes greatly depends on the electrochemical stability of water, and thus is generally limited to similar to 1.2 V. Herein, a 1.4 V potential window (vs Ag/AgCl) in the 5 M NaNO3 aqueous electrolyte for porous delta-MnO2 with a hierarchical interconnected nanosheet structure grown on electrochemically roughened graphite paper by electrodeposition is reported. A specific capacitance of similar to 407.6 F g(-1) is delivered at 1 A g(-1), and capacitance retention up to similar to 90.7% is achieved after 5000 cycles at 8 A g(-1). The aqueous asymmetric supercapacitors of 2.4 V are assembled with the configuration of delta-MnO2//activated carbon, and an energy density (E) of similar to 38.4 Wh kg(-1) is obtained at 599.7 W kg(-1) (even at 12 kW kg(-1), E of similar to 21.7 Wh kg(-1) is still delivered). Moreover, the asymmetric supercapacitors exhibit good rate and cycling performance. Thanks to the simple preparation for the electrode materials/structures and high device performance, it is believed that this work provides valuable contributions to developing aqueous supercapacitors delivering a broad working voltage window and thus an elevated energy density.

For aqueous supercapacitors, the working voltage is normally limited below 2 V because of the electrochemical stability of water, which limits improvement of the energy density and thus severely hinders their practical application. I lerem, a flexible electrode of interconnected delta-MnO2 nanosheets anchored on activated carbon cloth with a potential window (vs Ag/AgCl) extending to 1.2 V is developed using simple one-step water bath only at 40 degrees C. A high specific capacitance up to 360.5 F g(-1) at 1 A g(-1) combining with good rate performance and electrochemical stability is delivered. Folding test indicates that the charge storage performance of the electrode has neglected degradation during the 2000 times of folding. Furthermore, a 2.4 V aqueous asymmetric supercapacitor is assembled based on the device configuration of activated carbon//delta-MnO2 and a high energy density of 49.8 Wh kg(-1) at the power density of 1198.4 W kg(-1) and good electrochemical stability, i.e., 90.6%capacitance retention after 5000 cycles can be achieved. Thanks to the good energy storage performance, high flexibility and simple preparation of the material, it is believed that this work provides a valuable exploration to develop high-performance flexible aqueous asymmetric energy storage devices.