• Energy Research

A simple and scalable method has been developed to fabricate nanostructured MnO2-carbon nanotube (CNT)-sponge hybrid electrodes. A novel supercapacitor, henceforth referred to as "sponge supercapacitor", has been fabricated using these hybrid electrodes with remarkable performance. A specific capacitance of 1,230 F/g (based on the mass of MnO2) can be reached. Capacitors based on CNT-sponge substrates (without MnO2) can be operated even under a high scan rate of 200 V/s, and they exhibit outstanding cycle performance with only 2% degradation after 100,000 cycles under a scan rate of 10 V/s. The MnO2-CNT-sponge supercapacitors show only 4% of degradation after 10,000 cycles at a charge-discharge specific current of 5 A/g. The specific power and energy of the MnO2-CNT-sponge supercapacitors are high with values of 63 kW/kg and 31 Wh/kg, respectively. The attractive performances exhibited by these sponge supercapacitors make them potentially promising candidates for future energy storage systems.

Novel, noble-metal-free, solid-state all-titanium carbide (Ti3C2Tx) MXene microsupercapacitors are fabricated, which exhibit high areal capacitance, excellent rate-capability, and are transferable to any surface.

Abstract We report a versatile route for the preparation of metal phosphides using PH3 plasma for supercapacitor applications. The high reactivity of plasma allows rapid and low temperature conversion of hydroxides into monometallic, bimetallic, or even more complex nanostructured phosphides. These same phosphides are much more difficult to synthesize by conventional methods. Further, we present a general strategy for significantly enhancing the electrochemical performance of monometallic phosphides by substituting extrinsic metal atoms. Using NiCoP as a demonstration, we show that the Co substitution into Ni2P not only effectively alters the electronic structure and improves the intrinsic reactivity and electrical conductivity, but also stabilizes Ni species when used as supercapacitor electrode materials. As a result, the NiCoP nanosheet electrodes achieve high electrochemical activity and good stability in 1 M KOH electrolyte. More importantly, our assembled NiCoP nanoplates//graphene films asymmetric supercapacitor devices can deliver a high energy density of 32.9 Wh kg−1 at a power density of 1301 W kg−1, along with outstanding cycling performance (83% capacity retention after 5000 cycles at 20 A g−1). This activity outperforms most of the NiCo-based materials and renders the NiCoP nanoplates a promising candidate for capacitive storage devices.

Ultrasound is a source of ambient energy that is rarely exploited. In this work, a tissue-mimicking MXene-hydrogel (M-gel) implantable generator has been designed to convert ultrasound power into electric energy. Unlike the present harvesting methods for implantable ultrasound energy harvesters, our M-gel generator is based on an electroacoustic phenomenon known as the streaming vibration potential. Moreover, the output power of the M-gel generator can be improved by coupling with triboelectrification. We demonstrate the potential of this generator for powering implantable devices through quick charging of electric gadgets, buried beneath a centimeter thick piece of beef. The performance is attractive, especially given the extremely simple structure of the generator, consisting of nothing more than encapsulated M-gel. The generator can harvest energy from various ultrasound sources, from ultrasound tips in the lab to the probes used in hospitals and households for imaging and physiotherapy.

On-Chip energy storage is currently on high demand as its potentiality for compatible integration with flexible and miniaturized functional electronic devices. Conventional microfabrication has been the widely employed technique in fabricating interdigitated microsupercapacitor devices in a reliable manner. However, developing unconventional lithography techniques can be attractive interms of simplicity with minimal sophistication while not compromising the performance. Here, we propose a simple and versatile strategy to fabricate on-chip microsupercapacitors (MSCs) employing hand-written sacrificial marker ink patterns, both in lift-off and etching modes. As a prototype, this technique is demonstrated for the fabrication of conducting polymer MSCs involving poly(3,4-ethylenedioxythiophene), polyaniline and metal oxide electrode materials. Typical values of energy density in the range of 5-11 mWh/cm3 at power densities of 1-6 W/cm3 are achieved, that are comparable to thin film batteries and superior to the carbon and metal oxide based microsupercapacitors reported in the literature. Fabrication of microsupercapacitor devices on curved surfaces and multi-stack designs are additional assets of this technique. This innovative strategy may be broadened for scalable fabrication of a wide variety of on-chip energy storage devices.

Nanostructured and mesoporous cobalt oxide (Co3O4) nanowire in flower-like arrangements have been directly grown over flexible carbon cloth collectors using solvothermal synthesis for supercapacitor applications. Changes in the morphology and porosity of the nanowire assemblies have been induced by manipulating the calcination temperature (200–300 °C) of the one-dimensional (1-D) structures, resulting in significant impact on their surface area and pseudocapacitive properties. As the calcination temperature increases from 200 to 250 °C, the flower morphology gradually modifies to the point where the electrolyte could access almost all the nanowires over the entire sample volume, resulting in an increase in specific capacitance from 334 to 605 Fg−1, depending on the nanowire electrode morphology. The 300 °C calcination results in the breakdown of the mesoporous morphology and decreases the efficiency of electrolyte diffusion, resulting in a drop in pseudocapacitance after 300 °C. A peak energy density of 44 Wh kg−1 has been obtained at a power density of 20 kW kg−1 for the 250 °C calcined sample.

The materials that are used to make electrodes and their internal structures significantly affect microbial fuel cell (MFC) performance. In this study, we describe a carbon nanotube (CNT)–sponge composite prepared by coating a sponge with CNTs. Compared to the CNT-coated textile electrodes evaluated in prior studies, CNT–sponge electrodes had lower internal resistance, greater stability, more tunable and uniform macroporous structure (pores up to 1 mm in diameter), and improved mechanical properties. The CNT–sponge composite also provided a three-dimensional scaffold that was favorable for microbial colonization and catalytic decoration. Using a batch-fed H-shaped MFC outfitted with CNT–sponge electrodes, an areal power density of 1.24 W m−2 was achieved when treating domestic wastewater. The maximum volumetric power density of a continuously fed plate-shaped MFC was 182 W m−3. To our knowledge, these are the highest values obtained to date for MFCs fed domestic wastewater: 2.5 times the previously reported maximum areal power density and 12 times the previously reported maximum volumetric power density.

Abstract Organometal trihalide perovskite solar cells have recently attracted lots of attention in the photovoltaic community due to their escalating efficiency and solution processability. The most efficient organometallic mixed-halide sensitized solar cells often employ 2,2′7,7′-tetrakis-( N , N -di- p -methoxyphenyl-amine)-9,9′-spirobifluorene (spiro-MeOTAD) as the hole-transporting material. In this work, we investigated the effect of different atmospheric storage conditions, particularly vacuum, dry nitrogen, and dry air, on the photovoltaic performance of TiO 2 –CH 3 NH 3 PbI 3− x Cl x –spiro-MeOTAD solar cells. We found that spin coating of spiro-MeOTAD in an oxygen atmosphere alone was not adequate to functionalize its hole-transport property completely, and our systematic experiments revealed that the device efficiency depends on the ambient atmospheric conditions during the drying process of spiro-MeOTAD. Complementary incident photon to current conversion efficiency (IPCE), light absorption and photoluminescence quenching measurements allowed us to attribute the atmosphere-dependent efficiency to the improved electronic characteristics of the solar cells. Furthermore, our Fourier transform infrared and electrical impedance measurements unambiguously detected modifications in the spiro-MeOTAD after the drying processes in different gas environments. Our findings demonstrate that proper oxidization and p-doping in functionalizing spiro-MeOTAD play a very critical role in determining device performance. These findings will facilitate the search for alternative hole-transporting materials in high-performance perovskite solar cells with long-term stability.