The design and fabrication of efficient and inexpensive electrodes for oxygen evolution reaction (OER) is essential for energy-conversion technologies. Herein, high OER activity is achieved using hollow mesoporous NiCo2O4 nanocages synthesized via a Cu2O-templated strategy combined with coordination reaction. The NiCo2O4 nanostructures with a hollow cavity, large roughness and high porosity show only a small overpotential of ∼0.34 V at the current density of 10 mA cm−2 and a Tafel slope of 75 mV per decade, which is comparable with the performance of the best reported transition metal oxide based OER catalysts in the literature. Meanwhile, the positive impacts of the nanocage structure and the Ni incorporation on the electrocatalytic performance are also demonstrated by comparing the OER activities of NiCo2O4 nanocages with Co3O4 nanocages, NiCo2O4 nanoparticles and 20 wt% Pt/C. Moreover, the NiCo2O4 nanocages also manifest superior stability to other materials. All these merits indicate that the hollow mesoporous NiCo2O4 nanocages are promising electrocatalysts for water oxidation.

We report a solar-assisted microbial fuel cell (solar MFC) that can produce electricity through coupling a microbial anode with flower-like CuInS2 (CIS) as the photocathode. Scanning electron microscopy images displayed a hierarchical structure of CIS, which would be beneficial to facilitate electron transfer in MFC. The electrochemical and photo-responsive activity of CIS was investigated by cyclic voltammetry, linear sweep voltammetry (LSV) and photocurrent tests. We propose a hypothesized mechanism of MFC operation that light-responsive CIS generated electron–hole pairs and triggered bioanodes for electricity generation. LSV curves and photocurrent data displayed the flower-like CIS and showed enhanced photocurrent generation under visible light irradiation. Based on the improved photoelectrochemical properties, the solar MFC achieved a maximum power density of 0.108 mW cm−2 and a current density of 0.62 mA cm−2. CIS as a photocathode presents a comparable power density to Pt/C in MFC.

Three-dimensional (3D) hierarchical porous Co-containing N-doped carbon materials (HP-Co-CNs) have been successfully prepared for the first time by using cyanamide as a nitrogen source and poly(vinyl alcohol) (PVA) hydrogel-based composites as in situ templates. Remarkably, the resulting HP-Co-CNs possess controllable nitrogen content, high surface area, hierarchical interconnected macro-/mesoporous structure, and a certain amount of Co-Nx moieties which could act as active sites in the oxygen reduction reaction (ORR). In studying the application of HP-Co-CNs for the ORR, the HP-Co-CNs showed excellent electrocatalytic performance for a four-electron ORR, and longer-term stability and higher methanol tolerance then the commercial Pt/C electrocatalyst in alkaline medium, highlighting the importance of macropores for diffusion and a sufficient amount of active sites related to high specific surface area for improving the ORR performance.

A facile strategy to synthesize the novel composite paper of graphene nanosheets (GNS) coated Co3O4 fibers is reported as an advanced anode material for high-performance lithium-ion batteries (LIBs). The GNS were able to deposit onto Co3O4 fibers and form the coating via electrostatic interactions. The unique hybrid paper is evaluated as an anode electrode for LIBs, and it exhibits a very large reversible capacity (∼840 mA h g–1 after 40 cycles), excellent cyclic stability and good rate capacity. The substantially excellent electrochemical performance of the graphene/Co3O4 composite paper is the result from its unique features. Notably, the flexible structure of graphenic scaffold and the strong interaction between graphene and Co3O4 fibers are beneficial for providing excellent electronic conductivity, short transportation length for lithium ions, and elastomeric space to accommodate volume varies upon Li+ insertion/extraction.Keywords: anode; Co3O4 fiber; graphene paper; lithium-ion batteries;

A facile and controllable strategy for preparing three-dimensionally quasi-ordered macroporous (3DOM) TiO2 has been developed through in situ hydrolysis on poly(vinyl alcohol) (PVA) gelated crystalline colloidal array (GCCA) photonic crystal films. The presence of PVA hydrogel in the PVA GCCA results in a non-close-packed structure and an increase in the hydrophilic character of the template, which contribute to a more uniform wetting of the template during the infiltration process. The resulting 3DOM TiO2 as an anode material for lithium-ion batteries (LIBs) exhibits a high rate capability and excellent cycle performance. The method presented in this paper is versatile and can be expanded for preparing various quasi-order macroporous materials.

We describe the preparation and characterization of a novel type of core–shell hybrid material for application in a novel hydrogen peroxide biosensor, where the structure consists of a continuous gold shell that encapsulates the silica fiber. The SiO2@Au nanofibers had been synthesized by electrospinning silica sol, and then golden seeds were in situ grown on the fiber, lastly the gold-seeded silica fibers were further coated by continuous gold shells. The above nanocomposites had satisfactory chemical stability, excellent biocompatibility and efficient electron transfer property, which may have potential application for the highly sensitive chemical or biological sensors. Cyclic voltammetry (CV) was used to evaluate the electrochemical performance of the SiO2@Au nanocomposites at indium tin oxide (ITO). The biosensor showed high sensitivity and fast response upon the addition of H2O2 and the linear range to H2O2 was from 5 × 10−6 to 1.0 × 10−3 M with a detection limit of 2 μM (S/N = 3). The apparent Michaelis–Menten constant of the biosensor was 1.11 mmol L−1. These results indicated that SiO2@Au nanocomposites have potential for constructing of a variety of electrochemical biosensors.Highlights► We describe the preparation and characterization of SiO2@Au fibers for application in a novel hydrogen peroxide biosensor. ► The SiO2@Au hybrid fibers have high electron transport capacity and biocompatibility due to the perfect network and high surface-to-volume ratio. ► The designed HRP biosensor shows high sensitivity and fast response upon the addition of H2O2.

In this paper, we investigated the use of polyamidoamine (PAMAM) dendrimer-encapsulated platinum nanoparticles (Pt-DENs) as a promising type of cathode catalyst for air-cathode single chamber microbial fuel cells (SCMFCs). The Pt-DENs, prepared via template synthesis method, have uniform diameter distribution with size range of 3–5 nm. The Pt-DENs then loaded on to a carbon substrate. For comparison, we also electrodeposited Pt on carbon substrate. The calculation shows that the loading amount of Pt-DENs on carbon substrate is about 0.1 mg cm−2, which is three times lower than that of the electrodeposited Pt (0.3 mg cm−2). By measuring batch experiments, the results show that Pt-DENs in air-cathode SCMFCs have a power density of 630 ± 5 mW m−2 and a current density of 5200 ± 10 mA m−2 (based on the projected anodic surface area), which is significantly better than electrodeposited Pt cathodes (power density: 275 ± 5 mW m−2 and current density: 2050 ± 10 mA m−2). Additionally, Pt-DENs-based cathodes resulted in a higher power production with 129.1% as compared to cathode with electrodeposited Pt. This finding suggests that Pt-DENs in MFC cathodes is a better catalyst and has a lower loading amount than electrodeposited Pt, and may serve as a novel and alternative catalyst to previously used noble metals in MFC applications.Graphical abstractHighlights► Dendrimer-encapsulated platinum nanocomposites (Pt-DENs) and electrodeposited Pt nanoparticles are prepared as cathodic catalyst of MFCs. ► Compared to electrodeposited Pt- based cathode, the Pt-DENs/carbon paper cathode shows better electrochemical performance and catalytic activity. ► Pt-DENs has improved the oxygen reduction reaction in cathodes and increased the power output to 630 mW m−2.

The design and fabrication of efficient and inexpensive electrodes for oxygen evolution reaction (OER) is essential for energy-conversion technologies. Herein, high OER activity is achieved using hollow mesoporous NiCo2O4 nanocages synthesized via a Cu2O-templated strategy combined with coordination reaction. The NiCo2O4 nanostructures with a hollow cavity, large roughness and high porosity show only a small overpotential of ∼0.34 V at the current density of 10 mA cm−2 and a Tafel slope of 75 mV per decade, which is comparable with the performance of the best reported transition metal oxide based OER catalysts in the literature. Meanwhile, the positive impacts of the nanocage structure and the Ni incorporation on the electrocatalytic performance are also demonstrated by comparing the OER activities of NiCo2O4 nanocages with Co3O4 nanocages, NiCo2O4 nanoparticles and 20 wt% Pt/C. Moreover, the NiCo2O4 nanocages also manifest superior stability to other materials. All these merits indicate that the hollow mesoporous NiCo2O4 nanocages are promising electrocatalysts for water oxidation.

Three-dimensional (3D) hierarchical porous Co-containing N-doped carbon materials (HP-Co-CNs) have been successfully prepared for the first time by using cyanamide as a nitrogen source and poly(vinyl alcohol) (PVA) hydrogel-based composites as in situ templates. Remarkably, the resulting HP-Co-CNs possess controllable nitrogen content, high surface area, hierarchical interconnected macro-/mesoporous structure, and a certain amount of Co-Nx moieties which could act as active sites in the oxygen reduction reaction (ORR). In studying the application of HP-Co-CNs for the ORR, the HP-Co-CNs showed excellent electrocatalytic performance for a four-electron ORR, and longer-term stability and higher methanol tolerance then the commercial Pt/C electrocatalyst in alkaline medium, highlighting the importance of macropores for diffusion and a sufficient amount of active sites related to high specific surface area for improving the ORR performance.