We present a new approach to fabricate an integrated power pack by hybridizing energy harvest and storage processes. This power pack incorporates a series-wound dyesensitized solar cell (DSSC) and a lithium ion battery (LIB) on the same Ti foil that has double-sided TiO 2 nanotube (NTs) arrays. The solar cell part is made of two different cosensitized tandem solar cells based on TiO 2 nanorod arrays (NRs) and NTs, respectively, which provide an open-circuit voltage of 3.39 V and a short-circuit current density of 1.01 mA/cm 2 . The power pack can be charged to about 3 V in about 8 min, and the discharge capacity is about 38.89 μAh under the discharge density of 100 μA. The total energy conversion and storage efficiency for this system is 0.82%. Such an integrated power pack could serve as a power source for mobile electronics. KEYWORDS: Solar cell, lithium ion battery, TiO 2 nanotubes, mobile energy R ecently, nanostructures have been widely used in energy harvesting devices, such as dye-sensitized solar cells (DSSCs), nanogenerators, and fuel cells, due to their high efficiency and lightweight. 1−9 Among them, nanostructurebased DSSCs are likely to be low-cost, high efficiency, and simple in preparation, which is promising as a renewable energy resource for sustainable development of the future. 1,4,5,10 At the same time, nanostructures have been used in energy storage fields, such as lithium ion batteries (LIBs), due to their highenergy density and long cycle life. 11−14 These energy harvesting and storage approaches are developed as independent technologies but usually are used together as a power system. Traditionally, the power pack is based on a silicon solar panel and a solid-state lithium battery as the two independent parts, which is large, heavy, and inflexible. Therefore, in order to satisfy the special needs in some fields, hybridizing energy harvesting and storage units as an integrated power pack based on same nanostructured substrates may be an effective way to obtain a small size, lightweight, and high-density energy system.In this paper, we report a new integrated power system of DSSC and LIB to hybridize energy harvest and storage processes based on double-sided TiO 2 NTs grown on the same substrate. Double-sided TiO 2 NTs not only provide larger electrode area for DSSCs and LIBs but also can improve the electron transport properties of DSSCs and avoid irregular expansion when the insertion/removal of lithium along a specific orientation in anode material. 11,15 Compared with other integrated solar power supplies, 16,17 double-sided TiO 2 NTs with large area can be prepared by a simple, cost-effective, and controllable electrochemical process. Taking the advantages of the titanium (Ti) sheet substrate, the integrated power pack can be flexible and directly harvest and store energy by the electron conduction of the substrate. By using this hybird structure, the voltage of the power pack can be charged to ∼3 V in ∼8 min, and the discharge capacity is ∼38.89 μAh under the discharge densi...

Energy generation and energy storage are two distinct processes that are usually accomplished using two separated units designed on the basis of different physical principles, such as piezoelectric nanogenerator and Li-ion battery; the former converts mechanical energy into electricity, and the latter stores electric energy as chemical energy. Here, we introduce a fundamental mechanism that directly hybridizes the two processes into one, in which the mechanical energy is directly converted and simultaneously stored as chemical energy without going through the intermediate step of first converting into electricity. By replacing the polyethylene (PE) separator as for conventional Li battery with a piezoelectric poly(vinylidene fluoride) (PVDF) film, the piezoelectric potential from the PVDF film as created by mechanical straining acts as a charge pump to drive Li ions to migrate from the cathode to the anode accompanying charging reactions at electrodes. This new approach can be applied to fabricating a self-charging power cell (SCPC) for sustainable driving micro/nanosystems and personal electronics. KEYWORDS: Self-charging power cell, mechanical energy, piezoelectricity, lithium ion battery, electrochemistry E nergy conversion and storage 1−3 are the two most important technologies in today's green and renewable energy science, which are usually separated units designed on the basis of vastly different approaches. As for energy harvesting, depending on the nature of energy sources, such as solar, 4−7 thermal, 8 chemical, 9 and mechanical, 10,11 various mechanisms have been developed for effectively converting them into electricity. Take smaller scale mechanical energy as an example, piezoelectric nanogenerators (NGs) have been developed into a powerful approach for converting lowfrequency, biomechanical energy into electricity. 12−14 The mechanism of the NG relies on the piezoelectric potential created by an externally applied strain in the piezoelectric material for driving the flow of electrons in the external load. 12 As for energy storage, Li-ion battery 15−20 is one of the most effective approaches, in which the electric energy is stored as chemical energy through the migration of Li ions under the driving of an externally applied voltage source and the follow up electrochemical reactions occurring at the anode and cathode. 21 In general, electricity generation and energy storage are two distinct processes that are accomplished through two different and separated physical units achieving the conversions from mechanical energy to electricity and then from electric energy to chemical energy, respectively. Here, we introduce a fundamental mechanism that directly hybridizes the two processes into one, through which the mechanical energy is directly converted and simultaneously stored as chemical energy, so that the nanogenerator and the battery are hybridized as a single unit. Such an integrated self-charging power cell (SCPC), which can be charged up by mechanical deformation and vibration from the e...

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In the paper, we find that graphene has a strong dielectric loss, but exhibits very weak attenuation properties to electromagnetic waves due to its high conductivity. As polyaniline nanorods are perpendicularly grown on the surface of graphene by an in situ polymerization process, the electromagnetic absorption properties of the nanocomposite are significantly enhanced. The maximum reflection loss reaches À45.1 dB with a thickness of the absorber of only 2.5 mm. Theoretical simulation in terms of the Cole-Cole dispersion law shows that the Debye relaxation processes in graphene/ polyaniline nanorod arrays are improved compared to polyaniline nanorods. The enhanced electromagnetic absorption properties are attributed to the unique structural characteristics and the charge transfer between graphene and polyaniline nanorods. Our results demonstrate that the deposition of other dielectric nanostructures on the surface of graphene sheets is an efficient way to fabricate lightweight materials for strong electromagnetic wave absorbents.

Extraordinarily high reversible capacity of lithium-ion battery anodes is realized from SnO(2)/α-MoO(3) core-shell nanobelts. The reversible capacity is much higher than traditional theoretical results. Such behavior is attributed to α-MoO(3) that makes extra Li(2)O reversibly convert to Li(+).

We report a facile, solution-phase route to large-scale fabrication and characterization of single crystalline Cu 2 O nanowires with controllable diameter, different morphologies, and high aspect ratios. The synthesis of Cu 2 O nanowires is achieved by the reduction of cupric acetate with o-anisidine, pyrrole, or 2,5-dimethoxyaniline under hydrothermal conditions. The electrical properties of individual Cu 2 O nanowires have been examined by I−V characteristics. The output properties of Cu 2 O/poly(2,5-dimethoxyaniline) core/shell nanowires show n-type characteristics and improved conductivity, while those of Cu 2 O nanowires are linear. The results from this study provide a low-cost, naturally abundant nanostructured material for use in electronic devices.

The output of a piezoelectric nanogenerator (NG) fabricated using ZnO nanowire arrays is largely influenced by the density of the surface charge carriers at the nanowire surfaces. Adsorption of gas molecules could modify the surface carrier density through a screening effect, thus, the output of the NG is sensitive to the gas concentration. Based on such a mechanism, we first studied the responses of an unpackaged NG to oxygen, H2S and water vapor, and demonstrated its sensitivity to H2S to a level as low as 100 ppm. Therefore, the piezoelectric signal generated by a ZnO NWs NG can act not only as a power source, but also as a response signal to the gas, demonstrating a possible approach as a self-powered active gas sensor.

One-dimensional nanosized core/shell PN-junctions are formed from N-type SnO 2 nanorods (synthesized via a hydrothermal method; diameter ∼10 nm, length ∼100 nm) uniformly coated with P-type CuO nanoparticles (diameter ∼4 nm). Gas sensors are realized from these PN-junction nanorods, and their resistances greatly decrease upon exposed to H 2 S at room temperature. The sensitivity against 10 ppm H 2 S at 60 °C is up to 9.4 × 10 6 . At the same time, the sensors have very good selectivity against H 2 S. Such good performances are probably attributed to the destruction of PN-junctions and the small size effect of nanostructures. Our results imply that one-dimensional heterostructured nanomaterials are promising candidates for high-performance gas sensors.