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Defective cross linked nickel cobalt sulfide sheets dominated by phosphorus anions and a hetero interface were designed. The catalyst possesses surprising HER properties with low overpotentials and long term stability.

Oxygen defects and hollow structures positively impact pseudocapacitive properties of diffusion/surface-controlled processes, a component of critical importance when building high-performance supercapacitors. Hence, we fabricated hollow nickel/cobalt molybdate rods with O-defects (D-H-NiMoO 4 @CoMoO 4 ) via a soft-template and partial reduction method, enhancing D-H-NiMoO 4 @CoMoO 4 's electrochemical performance, yielding a specific capacitance of 1329 F g -1 , and demonstrating excellent durability with 95.8% capacity retention after 3000 cycles. D-H-NiMoO 4 @CoMoO 4 was used as the positive electrode to construct an asymmetric supercapacitor, displaying an energy density of up to 34.13 W h kg -1 and demonstrating good predisposition towards practical applications. This work presents an effective approach to fabricate and use hollow nickel/cobalt molybdate rods with O-defects as pseudo-capacitor material for high-performance capacitive energy storage devices.

In this work, for the first time, we managed to derive the hierarchical porous carbon (HPC) at a large scale from the carbonization of franchet groundcherry fruit peels. With the interconnected por...

A three-dimensional (3D) hollow CoWO4 composite grown on Ni-foam (3D-H CoWO4 /NF) based on a flower-like metal-organic framework (MOF) is designed by utilizing a facile dipping and hydrothermal approach. The 3D-H CoWO4 /NF not only possesses large specific areas and rich active sites, but also accommodates volume expansion/contraction during charge/discharge processes. In addition, the unique structure facilitates fast electron/ion transport of 3D-H CoWO4 /NF. Meanwhile, a series of characterization measurements demonstrate the appropriate morphology and excellent electrochemical performance of the material. The 3D-H CoWO4 /NF possesses a high specific capacitance of 1395 F g-1 , an excellent cycle stability with 89% retention after 3000 cycles and superior rate property. Furthermore, the 3D-H CoWO4 /NF can be used as a cathode to configurate an asymmetric supercapacitor (ASC), and 3D-H CoWO4 /NF//AC shows a good energy density (29.0 W h kg-1 ). This work provides a facile method for the preparation of 3D-hollow electrode materials with high electrochemical capability for advanced energy storage devices.

Binary transition metal oxides as electroactive materials have continuously aroused grumous attention due to their high theoretical specific capacitance, high valtage window, and multiple oxidation states. However, the tiny specific surface area, poor conductivity and unsatisfactory cycle stability limit their practical application. Hence, a synthetic strategy is designed to fabricate a dual-tasking hollow cube nickel ferrite (NiFe2O4) - based composite (NiFe2O4-NiCo-LDH@rGO) with hierarchical structure. The composite is constructed by firstly preparing hollow NiFe2O4 from cube-like Ni - Fe bimetallic organic framework (NiFe-MOF), and then integrating nickel cobalt layered double hydroxide (NiCo-LDH) nanowires, together with reduced graphene oxide (rGO) via pyrolysis in conjuction with hydrothermal method. The NiFe2O4 possessing cubic hollow structure contributes to a huge accessible surface area, meanwhile alleviates large volume expansion/contraction effect, which facilitates suffcient permeation of the electrolyte and rapid ion/charge transport, and results in high cycling stability. The introduction of layered NiCo-LDH results in hierarchical structure and thus offers maximum contact areas with electrolyte, which heightens the specific capacitance of obtained composite and enhances the electro-catlytic activity towards oxidation of glucose. Furthermore, rGO layer greatly improves the electrical conductivity and ion diffusion/transport capability of composite. Benefiting from the unique structure and individual components of NiFe2O4-NiCo-LDH@rGO composite, the electrode delivers a high specific capacitance (750 C g−1) and superb durability. Simultaneously, the asymmetrical device based on NiFe2O4-NiCo-LDH@rGO as positive electrode delivers remarkable energy density (50 Wh kg−1). Moreover, NiFe2O4-NiCo-LDH@rGO exhibits good sensing performance with a sensitivity of 111.86 µA/µM cm−2, the wide linear range of 3.500 × 10−5 − 4.525 × 10−3 M, and the detection limit of 12.94 × 10−6 M with a signal to noise ratio of 3. Consequently, the NiFe2O4-NiCo-LDH@rGO could provide a prospective notion constructing bifunctional materials with hollow-cube hierarchical structure in the field of supercapacitors and electrochemical sensors.

A three-dimensional (3D) hollow CoWO

Binary transition metal oxides as electroactive materials have continuously aroused grumous attention due to their high theoretical specific capacitance, high valtage window, and multiple oxidation states. However, the tiny specific surface area, poor conductivity and unsatisfactory cycle stability limit their practical application. Hence, a synthetic strategy is designed to fabricate a dual-tasking hollow cube nickel ferrite (NiFe

The use of high electrochemical active binary nickel-cobalt sulfides/phosphides/selenides (Ni-Co-X, X = S, P, Se) as electrochemical energy storage materials still has a space for improvement because they become electrochemically unstable during long-term use. Herein, a facile and cost-effective dual-ligand synergistic modulation tactic is described to substantially improve the durability of Ni-Co-X (X = S, P, Se) at the atomic level by partially substituting S, P, and Se ligands into the nickel-cobalt hydroxide precursor, respectively. Remarkably, the dual-ligand electrodes on Ni-foam achieve superior durability and high electrochemical activity when used as positive electrodes in supercapacitors. Impressively, the density functional theory calculations demonstrate that the OH ligand in NiCo

In order to enhance the accountability of certification authorities (CAs), certificate transparency (CT) is proposed to record CA-signed certificates in public logs. A certificate is accepted by CT-compliant browsers only if it is recorded in the logs, so that any fraudulent certificate will be detected by the domain owner in the public-visible logs. In practice, third-party monitors fetch certificates in the public logs to provide certificate search services, and the domain owner regularly searches all certificates issued for its domain from the third-party monitors to watch for suspicious ones among them. In this paper, we study the links of the CT framework among CAs, browsers, domain owners (or websites), third-party monitors, and log servers, and then analyze the security designs of each link. As an essential link of the CT framework which is proposed against TLS man-in-the-middle (MitM) attacks, the services of a thirdparty monitor shall be protected well against such attacks. We explore the TLS/HTTPS configurations of 8 well-known monitors and find that there are vulnerabilities of TLS MitM attacks. Thus, the attackers might first launch the MitM attacks on the very limited number of third-party monitors on the Internet and return manipulated certificate search results to domain owners, to conceal fraudulent certificates. The overall security guarantees of CT are jeopardized due to the weak protections of third-party monitors.

Single sign-on (SSO) is becoming more and more popular in the Internet. An SSO ticket issued by the identity provider (IdP) allows an entity to sign onto a relying party (RP) on behalf of the account enclosed in the ticket. To ensure its authenticity, an SSO ticket is digitally signed by the IdP and verified by the RP. However, recent security incidents indicate that a signing system (e.g., certification authority) might be compromised to sign fraudulent messages, even when it is well protected in accredited commercial systems. Compared with certification authorities, the online signing components of IdPs are even more exposed to adversaries and thus more vulnerable to such threats in practice. This paper proposes ticket transparency to provide accountable SSO services with privacy-preserving public logs against potentially fraudulent tickets issued by a compromised IdP. With this scheme, an IdP-signed ticket is accepted by the RP only if it is recorded in the public logs. It enables a user to check all his tickets in the public logs and detect any fraudulent ticket issued without his participation or authorization. We integrate blind signatures, identity-based encryption and Bloom filters in the design, to balance transparency, privacy and efficiency in these security-enhanced SSO services. To the best of our knowledge, this is the first attempt to solve the security problems caused by potentially intruded or compromised IdPs in the SSO services.

In this account, elm seeds are employed to prepare oxygen enriched porous carbon materials with three-dimensional honeycomb-like structure (HLPC). The HLPC demonstrates favorable specific capacitance of 501 F/g at 1 A/g. Moreover, the assembled HLPC//HLPC symmetrical device delivers 18.6 Wh/kg at 1310 W/kg and maintains 8.36 Wh/kg at 13090 W/kg, which is regarded as competitive electrode compared with the previously reported biomass carbon-based materials. The outstanding performance is attributed to exceptional oxygen content, which could significantly enhance the overall capacitance and improve the wettability of the electrode. This work holds great potential to realize high-efficient, eco-friendly and industrial-grade production of biomass-derived carbon materials for advanced energy storage applications.

Intense efforts have been made to design and prepare hierarchical porous electrode materials because of high specific surface area and fast ions transport. In this work, a facile strategy for the polyvinyl pyrrolidone (PVP)-induced assembly of two-dimensional NiCo-LDHs nanosheets into three-dimensional flower-like microspheres is developed. The multilevel NiCo-LDHs microspheres possess high specific surface area and sufficient porosity. Electrochemical analysis manifests that the multilevel NiCo-LDHs is rather outstanding, which shows a comparatively high specific capacity of 622 C/g at 1 A/g, favorable rate performance and excellent long-term stability. Moreover, an optimized asymmetrical supercapacitor using flower-like NiCo-LDHs as positive electrode yields a maximum energy density of 63.4 Wh/kg at 934 W/kg. This work draws a promising way for the assembly of multidimensional configurations with immense prospect in energy-storage fields.

Constructing the porous graphitic carbon materials based on the renewable biomass-derived raw materials has raised widely attention in recent years. Herein, this work proposes a cost-effective and eco-friendly approach for fabricating the highly graphitic porous carbon (HGPC) materials using leaves of viburnum sargenti for the first time. The as-prepared carbon sample exhibits a moderate specific surface area of 762.3 m2/g, a high oxygen content of 16.75 at.%, which could contribute additional pseudocapacitance during electrochemical reaction process. And the doping of nitrogen atom (0.53 at.%) could availably improve the conductivity. Consequently, the HGPC electrode delivers an excellent specific capacitance of 612.8 F/g at 0.5 A/g and a remarkable cycling stability with 96.02% capacitance retention over 10,000 cycles. Additionally, the assembled HGPC//HGPC symmetric supercapacitor presents an ultrahigh energy density of 25.6 Wh/kg at the power density of 450 W/kg. This facile technique holds great promise to offer an effective and universal methodology for fabricating renewable biomass-derived carbon materials for high-performance supercapacitors.

Nickel cobalt selenides derived from metal organic framework have allured a lot of attention in energy storage areas. Herein, Nickel cobalt selenides (H-Ni-Co-Se) nanoarrays with hollow structure from pentagon-like Ni/Co-ZIF are successfully assembled on Ni-foam by employing sequential chemical etching and selenylation strategy. The hollow configuration grown on Ni-foam could offer rich electroactive region, shorten charge/ion diffusion length and enhance mass/electrons transfer. The as-prepared H-Ni-Co-Se delivers a favorable specific capacitance of 1175 F/g at 1 A/g, fast charge/discharge rate and excellent long-term stability. This versatile strategy can be extended to construct other transition metal compounds with outstanding electrochemical performance.

Apperceive to the environment is the basic attribute of Agent. Different environment requires Agent to adopt different perception methods. In this paper, we aim at publish/subscribe message environment, regard event as perceptive object, advance a reticulate event composition mechanism, construct a model of the perception body which is suitable for asynchronous cooperation of Agents, give the definition, mechanism of realization and evaluation of application of this model.