Jiewu Cui

A facile synthesis of mesoporous Co3O4/CeO2 hybrid nanowire arrays for high performance supercapacitors

The development of porous yet densely packed nanomaterials with high ion-accessible surface area and long cycling life is critical to the realization of high-density electrochemical capacitive energy storage. In this paper, we report a facile hydrothermal method to fabricate Co3O4/CeO2 hybrid nanowire arrays (NWAs). Supercapacitors based on the as-prepared mesoporous Co3O4/CeO2 hybrid NWAs exhibit excellent pseudocapacitive performance with a capacitance of 4.98 F cm−2 at 10 mA cm−2 (1037.5 F g−1 at 2.08 A g−1) and only a small capacitance loss of 5.6% after 5000 charge/discharge cycles. The remarkable pseudocapacitance and superior stability suggest that mesoporous Co3O4/CeO2 hybrid NWAs are promising candidates for supercapacitor applications.

Integration of a highly ordered gold nanowires array with glucose oxidase for ultra-sensitive glucose detection.

A highly sensitive amperometric nanobiosensor has been developed by integration of glucose oxidase (GO(x)) with a gold nanowires array (AuNWA) by cross-linking with a mixture of glutaraldehyde (GLA) and bovine serum albumin (BSA). An initial investigation of the morphology of the synthesized AuNWA by field emission scanning electron microscopy (FESEM) and field emission transmission electron microscopy (FETEM) revealed that the nanowires array was highly ordered with rough surface, and the electrochemical features of the AuNWA with/without modification were also investigated. The integrated AuNWA-BSA-GLA-GO(x) nanobiosensor with Nafion membrane gave a very high sensitivity of 298.2 μA cm(-2) mM(-1) for amperometric detection of glucose, while also achieving a low detection limit of 0.1 μM, and a wide linear range of 5-6000 μM. Furthermore, the nanobiosensor exhibited excellent anti-interference ability towards uric acid (UA) and ascorbic acid (AA) with the aid of Nafion membrane, and the results obtained for the analysis of human blood serum indicated that the device is capable of glucose detection in real samples.

Enhanced visible-light photoelectrochemical behaviour of heterojunction composite with Cu2O nanoparticles-decorated TiO2 nanotube arrays

Heterojunction composites based on n-type TiO2 nanotubes arrays (TNAs) coupled with p-type Cu2O nanoparticles were synthesized using a square wave voltammetry deposition method for in situ deposition of Cu2O nanoparticles onto the inner surfaces and interfaces of TNAs. The prepared samples were characterized by field-emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and UV-vis spectroscopy. When compared with pure TNAs, the Cu2O–TNAs heterojunction composites exhibit considerably higher photocurrent density under visible-light irradiation and enhanced photocatalytic activity for the visible-light-driven photodegradation of methyl orange. Moreover, the photocurrent densities and photocatalytic activity of the Cu2O–TNAs heterostructures largely depend on the deposition potential which determines the content of the Cu2O nanoparticles. The Cu2O–TNAs prepared by the deposition potential of −1.0 V showed the highest photocurrent density (0.91 mA cm−2) and the largest photodegradation rate of methyl orange (88.8%) at the applied potential of 0.5 V under visible light irradiation. The enhanced photoelectrocatalytic activity can be attributed to reducing the recombination rate of the photoexcited electron–hole pairs in TNAs when coupled with Cu2O nanoparticles.

Flow-through TiO2 nanotube arrays: a modified support with homogeneous distribution of Ag nanoparticles and their photocatalytic activities

Silver decorated TiO2 nanotube arrays (TNTAs) show great potential applications for photocatalysis and gas sensors. In this work, we report an improved strategy to modify the morphology of flow-through TiO2 nanotube arrays (f-TNTAs) for homogeneous Ag nanoparticle loading, and their photocatalytic activities are also investigated. Firstly, TNTAs were fabricated by potentiostatic anodization in fluoride-containing electrolytes. Subsequently, a high voltage was immediately exerted, and then a low potential was applied at the end of anodization process. The as-prepared f-TNTAs with improved bottom morphologies were finally obtained. This new kind of support was immersed in AgNO3 solution, and then the absorbed silver ions were reduced to metallic Ag0 by UV light. Compared with conventional TiO2 nanotube arrays (c-TNTAs), the modified f-TNTAs show a better ability for the dispersion of Ag nanoparticles (Ag NPs) in different regions (upper, central and bottom region) of the nanotubes. A series of testing measures (XPS, EDX, SEM and XRD) were adopted to confirm this facile process. Ag decorated f-TNTAs were used as photocatalysts for the degradation of Methyl Orange (MO) under UV light. The degradation rate could reach 54% in 10 min, and the complete degradation of MO was observed after 30 min. These results were much better than that of Ag decorated c-TNTAs. The modified f-TNTAs via our method can also be used to couple with other noble metals or compound semiconductors. These composite structures are expected to find potential applications in photoelectric devices, gas sensors, and photocatalysis.

Supercapacitive performance of electrochemically doped TiO2 nanotube arrays decorated with Cu2O nanoparticles

Highly ordered TiO2 nanotube arrays (TNAs) with enhanced electronic conductivity treated by introducing oxygen vacancies have been considered to be a promising electrode material for supercapacitors. In this work, we fabricated electrochemically doped TiO2 nanotube arrays (ED-TNAs) through a facile cyclic voltammetry method, and then deposited the uniformly dispersed Cu2O nanoparticles onto ED-TNAs to synthesise a high performance electrode for a supercapacitor. The ED-TNAs electrode exhibited a high specific capacitance of 5.42 mF cm−2 at a scan rate of 10 mV s−1, which was about 59 times higher than for the pristine TNAs electrode. Moreover, the ED-TNAs were demonstrated to be an appropriate support for Cu2O nanoparticles. The highest specific capacitance of the Cu2O/ED-TNAs electrode could reach 198.7 F g−1 at the current density of 0.2 A g−1, and approximately 88.7% of the initial capacitance was retained after 5000 cycles of galvanostatic charge–discharge.

Supercapacitive performance of hydrogenated TiO2 nanotube arrays decorated with nickel oxide nanoparticles

Highly ordered self-organized TiO2 nanotube arrays (TNTAs) could not only be used as current collectors, but also adopted as highly ion-accessible and charge transfer-channels for the construction of supercapacitors. In this paper, hydrogenated TNTAs were obtained and then nickel oxide (NiOx) nanoparticles were successfully deposited onto the inner surface and interface of HTNTAs through a cyclic voltammetry electrochemical deposition process (NiOx/HTNTAs). The FESEM images of the samples showed that the diameter of the NiOx nanoparticles ranged from 7 to 60 nm. The as-fabricated NiOx/HTNTAs exhibited an obviously pseudocapacitive performance with a specific capacitance of 689.28 F g−1 at a current density of 1.5 A g−1 and 91.9% of the initial capacitance remaining after 5000 charge/discharge cycles at a current density of 3 A g−1 in 1 M KOH. This work reveals a feasible and green method for the fabrication of TNTAs modified with electroactive metal oxide nanoparticles as functional electrode materials for supercapacitors.

Integration of mesoporous nickel cobalt oxide nanosheets with ultrathin layer carbon wrapped TiO2 nanotube arrays for high-performance supercapacitors

Decorated TiO2 nanotube array-based electrodes for supercapacitors are successfully fabricated by a facile and green process in this paper. Firstly, TiO2 nanotube arrays are modified with ultrathin carbon layers by in situ pyrolysis with residual ethylene glycol from anodization as a carbon resource, then electroactive materials, nickel cobalt oxides with different stoichiometric nickel and cobalt contents, are synthesized by chemical bath deposition and a controlled post-calcination process. The sample demonstrates a superb specific capacitance of 934.9 F g−1 at a current density of 2 A g−1 and a better rate capability of 865.8 F g−1 at 20 A g−1 while maintaining 92.6% capacity after 5000 cycles at a high current density of 10 A g−1. The outstanding supercapacitive performance is attributed to the unique hierarchical mesoporous architectures and the desirable design of the nanocomposites, and it also suggests that carbon modified TiO2 nanotube arrays decorated with nickel cobalt oxides are promising candidates for supercapacitor applications.

A novel ultrasensitive phosphate amperometric nanobiosensor based on the integration of pyruvate oxidase with highly ordered gold nanowires array.

A novel phosphate amperometric nanobiosensor, based on an intimate integration of pyruvate oxidase (PyOx) and its cofactors, thiamine pyrophosphate (TPP) and flavin adenine dinucleotide (FAD), with a highly ordered gold nanowires array (AuNWA) has been developed. The successful integration of PyOx and the co-factors, via crosslinking with bovine serum albumin (BSA) and glutaraldehyde (GLA), onto the AuNWA was confirmed by cyclic voltammetry and amperometry. The resulting nanobiosensor achieved a detection limit of 0.1 µM, a linear concentration range of 12.5-1000 µM, and a sensitivity of 140.3 µA mM(-1)cm(-2). Notably, the incorporation of the AuNWA reduced the required PyOx concentration by 70-120 fold and the presence of common interferants, such as chloride, sulfate, fluoride, nitrite and nitrate ions did not interfere with phosphate detection. Furthermore, the nanobiosensor demonstrated a very high stability with repeated use over two weeks and was successfully used for the determination of phosphate in water samples with an average recovery of 96.6 ± 4.9%.

Electrochemical hydrogenated TiO2 nanotube arrays decorated with 3D cotton-like porous MnO2 enables superior supercapacitive performance

Highly ordered TiO2 nanotube arrays (TNTAs) have shown great promise to serve as an efficient current collector as well as an outstanding support for the application of constructing high performance supercapacitor electrode materials. In this study, a novel-structured MnO2/EH-TNTAs electrode with superior supercapacitive performance was developed by galvanostatic electrodeposition of MnO2 nanoflakes onto both the outer and inner walls of electrochemically hydrogenated TNTAs (EH-TNTAs). The as-fabricated MnO2/EH-TNTAs electrode could achieve a specific capacitance of up to 650.0 F g−1 at 1.0 A g−1 with 86.9% of the initial capacitance remaining after 5000 charge/discharge cycles at 5 A g−1, outperforming other reported TNTAs-based electrodes. The prominent supercapacitive performance of MnO2/EH-TNTAs electrode could be attributed to the unique 3D cotton-like porous structure and high specific surface area of MnO2 deposit as well as the remarkably improved electrical conductivity and electrochemical performances of EH-TNTAs induced by the introduction of oxygen vacancies during the electrochemical hydrogenation process. This work offers theoretical insight and practical guidelines for TNTAs-based electrodes applied for high-performance supercapacitors as well as other energy storage devices.

Hierarchical three-dimensional MnO2/carbon@TiO2 nanotube arrays for high-performance supercapacitors

Highly ordered TiO2 nanotube arrays (TNAs) modified by other materials with enhanced conductivity and capacitance have been considered to be promising anode materials for supercapacitors. In this work, carbon@TiO2 nanotube arrays (CTNAs) were firstly synthesized through a calcination process under an Ar atmosphere. Then the hierarchical three-dimensional MnO2/carbon@TiO2 nanotube arrays (CMTNAs) were further developed via hydrothermal deposition of uniformly dispersed MnO2 nanoparticles with the help of the in situ reduction effect of the as-obtained carbon layers. The CTNA electrode exhibited a high area capacitance of 5.58 mF cm−2 at a scan rate of 100 mV s−1, which is about 11 times higher than that of the TiO2 nanotube arrays annealed under an air atmosphere (ATNAs). The highest gravimetric capacitance 521.4 A g−1 was achieved with the CMTNAs at a current density of 2 A g−1, and 88.6% of the initial capacitance could be maintained at a current density of 5 A g−1 up to 2000 cycles via a galvanostatic charge–discharge test.