Applications In Energy Devices Research Articles

Effect of design of assisting devices on the lower body muscular activities during gait with crutch executed by amputees

Chemical sensing is an important yet less developed part of Internet of things technology as it generates chemical information that is highly relevant in environment monitoring, public health, and industrial safety. To this end, nano-electronic sensory and signal transmission devices have the best technological and commercial potential for its compatibility with the existing electronic devices. The search for suitable and high-performance sensing materials and their proper incorporations into the micro-/nano-electronic platforms hold the key. For materials, nanocomposites based on graphitic carbon nanomaterials and other functional building blocks, one for signal transduction and one for molecular recognition, respectively, have achieved tremendous success in the application of chemical sensors and energy devices due to their tunable complexity and functionality. Here we summarize the design, synthesis, and device fabrication of nanocomposite materials based on single-walled carbon nanotubes and graphene, with functional building blocks including conducting polymers, metal, metal oxide, etc. Novel chemical approaches have been developed for the assembly of different building blocks, as well as their applications in chemical sensing, breath diagnostics, and energy applications. Based on the fundamental working principles of nano-electronic chemical sensing, we further demonstrate an on-chip nano-electronic-based chemical signaling technique for the investigation and improvement of sustainable energy technologies. Through the development of a novel on-chip electrical transport spectroscopy approach, we demonstrate that the electrical properties of ultrafine platinum nanowires are highly sensitive and selective to the electrochemical surface states, enabling an in situ nano-electronic signaling pathway that reveals electrochemical interface information in various energy conversion reactions. Through the new insights and newly identified nano-electronic indicators, we further demonstrate the rationally designed strategies for enhanced performance (activity, poisoning resistance, and lifetime) of energy conversion devices. Furthermore, systematic on-chip nano-electronic investigations of bioelectrochemical systems help to elucidate the complex basis of electrical conductivity of both individual microbial cells and biofilms, which will accelerate our basic understanding of earth’s microbiomes and harness the capabilities of microbial ecosystems.

Optoelectronic and thermoelectric properties of double perovskite Rb2PtX6 (X = Cl, Br) for energy harvesting: First-principles investigations

The double perovskite materials have attracted broad interest of researchers in recent years because of their potential applications in renewable energy. This work comprehensively explore optoelectronic and thermoelectric properties of Rb2PtCl6 and Rb2PtBr6 of double perovskite for renewable energy applications. The structural and thermodynamic stabilities are ensured by calculating their tolerance factor, formation energy and phonon dispersion. The Rb2PtCl6 and Rb2PtBr6 exhibited bandgaps of magnitude 2.62 and 2.10 eV. Maximum absorption occurred in the visible range for Rb2PtBr6, which shifted to the ultraviolet region when Br is replaced with Cl that ensures their effective utilization for solar cells and other optoelectronic applications. Furthermore, the thermoelectric behavior of these materials by semi-classical Boltzmann theory-based BoltzTraP code. The trends of thermoelectric parameters of Rb2PtBr6 deviate from the trends of Rb2PtCl6 at above 300 K. The figure of merit (ZT) reveals reasonable thermoelectric performance in the low-temperature zone. Our present study is believed to open an avenue of research for the potential applications in next-generation renewable energy devices.

Bismuth and zinc co-modified Mn1·1Co1·5Fe0·4O4 negative temperature coefficient sensitive ceramics: Structural and electrical characterization

Manganese-based spinel oxides (Mn1·1Co1·5Fe0·4O4) are gaining widespread attention due to their extensive applications in sensors and energy devices. A drawback is their high synthesis temperature and difficult regulation of electrical parameters. As a remedy, Bi2O3–ZnO dual-additives were used. Eventually, the Bi2O3–ZnO co-modified Mn1·1Co1·5Fe0·4O4 ceramics were successfully fabricated with a lower sintering temperature at 1060 °C. More importantly, the incorporation of Zn ions can effectively adjust the electrical properties of the Mn1·1Co1·5Fe0·4O4 ceramics, especially the resistivity and B constant. The resulting ρ25 and B25/50 were 880–1694 Ω cm and 3697–3989 K, respectively. The potential cation distributions and hopping conduction mechanism are clarified clearly in combination with X-ray photoelectron spectroscopy analysis.

High-performance silver nanowire-based thermopolyurethane flexible conductive films

With the unique flexibility or ductility, and efficient low-cost manufacturing process, flexible electronic devices have attracted a growing interest in scientific research and industry with applications in wearable electronic devices, stretchable antennas, flexible displays, and energy devices. Flexible conductive film (FCF), which functionalizes in building connections between different components of the devices, is key constitutions in flexible devices. We prepared the flexible conductive film with a diameter of approximately 60 nm and a length of 20 μm of silver nanowires (AgNWs) as the fillers and thermopolyurethane (TPU) as the matrix by solution blending and tape casting method. Further, self-made fluorinated decyl polyhedral oligomeric silsesquioxane (F-POSS) as hydrophobic layer was deposited on the AgNWs-TPU conductive film by immersing method. We systematically studied the properties of electronic conductivity, electrothermal response and infrared radiation (IR) thermal response performances, and superhydrophobic performance of AgNWs-TPU conductive films. The experimental results reveal that as the mass content of AgNWs reaches 30 wt%, the film displays good conductivity, and the resistivity of the film with 40 wt% AgNWs is 0.07 Ω·mm. AgNWs-TPU conductive film has good electrothermal response and IR thermal response performances. The water contact angle of the AgNWs-TPU conductive film with superhydrophobic layer reaches 155.29° ± 1.03 and superhydrophobic AgNWs-TPU conductive film slightly improves the reliability and tensile strength of the AgNWs-TPU conductive film. Our experimental results indicate that the superhydrophobic flexible conductive films prepared in this experiment can be applied to wearable flexible devices.

Sandwiched Cu7S4@graphite felt electrode for high performance aqueous polysulfide/iodide redox flow batteries: Enhanced cycling stability and electrocatalytic dynamics of polysulfides

Aqueous polysulfide/iodide redox flow battery (RFB) with highly soluble active species are attractive candidates for scalable energy storage, offering noticeable reduced RFB cost. Though, poor reversibility and electrochemical activity of the redox reaction of polysulfide couples on graphite felt electrode restricts its energy efficiency. Herein, a facile method to improve the electrocatalytic activity by fabrication of skeletal Cu7S4 hollow nanocages with copper vacancies is presented. Cu7S4 nanoparticles can selectively boost the electrocatalytic activities of S2−/Sx2- redox reactions and suppress the hydrogen evolution side reaction. In addition, the hollow opening structure of skeletal Cu7S4 served as the catalytic active site (both the inner side and outer surface), accelerating the electrolyte transport and promoting the charge transfer process. A sandwiched electrode was constructed by coating Cu7S4 nanocages into the interlayer of graphite felt. The polysulfide/iodide flow battery with SKE-Cu7S4 sandwich structure electrode can generate high energy efficiency of 78.5% at 20 mA cm−2, power density of 30.6 mW cm−2 and a stable energy efficiency retention of 92% after approximately 200 continuous cycles suggesting their potential use for future scalable RFBs. The developing of highly efficient and stable electrocatalyst for the electro-conversion of polysulfides will boost the performance and application of polysulfide-based flow batteries and other energy devices involved with polysulfides such as, quantum dots sensitized solar cells, Li–S batteries.

Reversible Transformation between Bipolar Memory Switching and Bidirectional Threshold Switching in 2D Layered K-Birnessite Nanosheets.

Birnessite-related manganese dioxides (MnO2) have recently been studied owing to their diverse low-dimensional layered structures and potential applications in energy devices. The birnessite MnO2 possesses a layered structure with edge-shared MnO6 octahedra layer stacked with interlayer of cations. The unique layered structure may provide some distinct electrical properties for the 2D layered nanosheets. In this work, layered K-birnessite MnO2 samples are synthesized by a hydrothermal method. The resistive switching (RS) devices based on single K-birnessite MnO2 nanosheets are fabricated by transferring the nanosheets onto SiO2/Si substrates through a facile and feasible method of mechanical exfoliation. The device exhibits nonvolatile memory switching (MS) behaviors with high current ON/OFF ratio of ∼2 × 105. And more importantly, reversible transformation between the nonvolatile MS and volatile threshold switching (TS) can be achieved in the single layered nanosheet through tuning the magnitude of compliance current (Icc). To be more specific, a relatively high Icc (1 mA) can trigger the nonvolatile MS behaviors, while a relatively low Icc (≤100 μA) can generate volatile TS characteristics. This work not only demonstrates the memristor based on single birnessite-related MnO2 nanosheet, but also offers an insight into understanding the complex resistive switching types and relevant physical mechanisms of the 2D layered oxide nanosheets.

(Invited) 2D Tellurene for Novel Electronics and Sensors

In this talk, I will discuss our recent progress in controllable synthesis of tellurene for electronics and sensor applications. The solution-synthesized tellurene crystals exhibit process-tunable thickness from a monolayer to tens of nanometers, lateral sizes ~ 100 mm, and can be transferred to designer substrates. I will further discuss our findings in 2-D tellurene’s material properties, as well as our efforts in the prototypical device explorations with the acquired fundamental understandings of tellurene’s properties. Our results show that the air-stable tellurene, as an emerging 2-D material, exhibits a plethora of intriguing physical properties appealing for applications in electronics, optoelectronics, energy, sensors, and quantum devices.

Rapid thermal annealing assisted facile solution method for tungsten-doped vanadium dioxide thin films on glass substrate

Abstract Vanadium dioxide VO2 is an important thermochromic material with useful applications in smart energy devices. This paper describes the synthesis of high-quality vanadium dioxide thermochromic thin films directly on glass substrate without any barrier layer prepared using a simple solution method. We demonstrate that 50 nm thick VO2 films display excellent visible transmittance (76.9% on glass, 69.4% on fused silica) and a large NIR switching efficiency (33.8% on glass, 44.3% on fused silica) at 1600 nm. It is found that the metal to semiconductor phase transition temperature Tc of undoped films can be reduced from a theoretical value of 68 °C to 49.4 °C by rapid thermal annealing. With W doping a continuous drop in the Tc is observed and for VO2 with 2% W doping, a Tc of 25.8 °C is achieved. These good optical properties and the near room-temperature phase transition temperature suggest that solution processing with the rapid thermal annealing process is a feasible method to obtain this promising material on glass substrate for practical application in thermochromic smart windows.

Design and tailoring of inks for inkjet patterning of metal oxides.

Inkjet printing has become a promising, efficient, inexpensive, scalable technique for materials deposition, mask-less and digital patterning in many device applications. Meanwhile, the ink preparation remains a challenge especially for printing functional oxide materials. Based on the principles of inkjet printing (especially relevant for piezoelectric drop-on-demand inkjet printer) and the process of the conversion of liquid ink into solid thin films of oxide materials, we present two approaches to the design and tailoring of inks: (i) oxide particle suspensions (e.g. SiO2, TiO2, Fe3O4) and (ii) metal-acetates precursor solutions for directly printing oxide thin films (e.g. ZnO, MgO, ITO and so forth). The solution inks are stable and produce tunable oxide films with high density and smooth surface. For some of the inks containing multi-type acetates with possible phase separation even before calcinations, we have developed a chelating procedure in order to tailor the films into single-phase homogeneity. The work lays a foundation for inkjet printing of oxides films for functional applications in electronic, photonic and energy devices.

Carbon Quantum Dot Incorporated Nickel Pyrophosphate as Alternate Cathode for Supercapacitors

AbstractIn spite of its large theoretical capacitance, the crystal structure of transition metal pyrophosphates frequently endures sluggish charge transfer and volume expansion leading to severe structural instability which may be ascribed to low power density and constant intercalation and deintercalation of ions in the matrix. Due to the stated facts, it resulted in quick capacity degradation and limited the overall performance of the energy device. To overcome the stated facts, we report the electrochemical charge storage performances of Nickel pyrophosphate/Carbon quantum dot (Ni2P2O7/CQD) nanocomposites. Here, we adopted a facile technique to prepare biowaste derived CQD and composited it with transition metal (Nickel) pyrophosphate. Incorporation of carbon quantum dots not only increased the specific capacitance than bare, besides, it also provides a long‐run cyclability. The addition of CQDs to the matrix favors rapid charge transfer and buffered the mechanical stress of nanocomposite. Using power law, the capacitance contribution from diffusion‐controlled and capacitive type mechanisms to the total specific capacitance was also elucidated. Hence the cost‐effective, facile synthesis method and favorable redox reaction empowered with voltage would have a potential application in high energy devices.

Advanced Exfoliation Strategies for Layered Double Hydroxides and Applications in Energy Conversion and Storage

AbstractAlong with the increasing aggravation of energy and environmental problems, the demand and utilization of renewable energy have increased. The rational design of advanced functional materials serves as a critical point for the improvement of performance and the practical application in renewable energy devices. Layered double hydroxides (LDHs) with 2D layered structures are promising energy materials for their unique physical and chemical properties. Nevertheless, the applications are limited by the structure of stacking with irrational electronic structure, sluggish mass transfer, and low activity. The exfoliation of LDHs into single‐ or few‐layered nanosheets appears to be a promising approach to overcome the above disadvantages. Herein, the recent progress on the development of exfoliation strategies for LDHs including liquid phase exfoliation, plasma‐induced exfoliation, and other advanced exfoliation strategies is highlighted and the applications in energy conversion and storage are systematically introduced.

A Review of Dry Spun Carbon Nanotube Yarns and Their Potential Applications in Energy and Mechanical Devices

A Review of Dry Spun Carbon Nanotube Yarns and Their Potential Applications in Energy and Mechanical Devices

Plasma-digital nexus: plasma nanotechnology for the digital manufacturing age

Digital transformation in manufacturing is one of the key megatrends in the development of the global economy and society. Three-dimensional (3D) printing is a transformative digital technology poised to disrupt manufacturing and supply chains across major industries. Here we critically examine relevant insights into current and emerging applications of plasma nanotechnology in printing, including 3D printing. Plasma devices operated at atmospheric pressure coupled with printing processes may help strengthen 3D printing as an emerging fabrication technology that morphs diverse metal powders, polymers, plastics and other materials into digitally designed 3D shapes and patterns. We discuss how plasma applications may help overcome current limitations of 3D printing in various fields, e.g., limitations of sculpting composite materials, lack of mechanical strength and the need for post-processing. Our key focus is on the challenges, opportunities and physical mechanisms of the use of 3D printing in nano-manufacturing, defined as the fabrication of nanoscale building blocks, such as nanoparticles and nanomaterials; their assembly into higher-order (microscale) structures; and the integration of these structures into larger (macro-) scale devices and systems by controlling energy and matter at the nanoscale. Moreover, we discuss the physico-chemical mechanisms that result in highly-conformal deposition of nanostructured materials onto 3D surfaces with microscopic (and possibly nanoscale) control of textures and inter-layer crosslinking, without the need for additional heating. We further highlight the opportunities that arise for plasma nanotechnology to synergize with the emerging digital transformation platforms in surface micro- and nano-structuring using polymers, metals, metallic alloys, and other materials. These new findings in plasma-digital nanoscale fabrication may lead to a new digital manufacturing platform suitable for a number of cutting-edge applications in electronic, sensing and energy devices.

Electronic properties of bare and functionalized two-dimensional (2D) tellurene structures.

Recently, 2D tellurene (Te) structures have been experimentally synthesized. These structures possess high carrier mobility and stability which make them ideal candidates for applications in electronics, optoelectronics and energy devices. We performed density functional theory (DFT) and molecular dynamics (MD) simulations to investigate the stability and electronic structure of 2D α- and β-Te sheets, and hydrogen, oxygen, and fluorine functionalized counterparts, including spin-orbit coupling effects. Our calculations show that bare α and β-Te sheets are stable with band gaps of 0.44 eV and 1.02 eV respectively. When functionalized, α and β monolayers exhibit metallic properties, except for hydrogenated β-Te, which exhibits semiconducting properties with a band gap of 1.37 eV. We see that H, O and F destabilize the structure of α-Te. We also find that F and H cause β-Te layers to separate into functionalized atomic chains and O causes β-Te to transform into a Te3O2-like structure. We also studied single atom and molecule binding on the Te surface, the effects of adatom coverage, and the effects of functionalized Te on a GaSe substrate. Our results indicate that tellurene monolayers and functionalized counterparts are not only suitable for future optoelectronic devices, but can be used as metallic contacts in nanoscale junctions.

Pyridinic and graphitic nitrogen-enriched carbon paper as a highly active bifunctional catalyst for Zn-air batteries

Pyridinic and graphitic nitrogen are recognized as the most promising dopants for promoting oxygen reactions since they are beneficial to the formation of corresponding C–N bonds as efficient active sites. However, complete control of such efficient nitrogen-doping sites in carbon materials is difficult to realize in practice in a pyrolysis process. Here, we present maximized pyridinic and graphitic nitrogen-doped oxygen electrode via the precise use of nitrogen-containing precursors and carbonization temperature. The critical roles of pyridinic and graphitic nitrogen dopants in enhancing oxygen reaction activity are unraveled and this highly active material exhibits a remarkable half-wave potential of 0.89 V versus the reversible hydrogen electrode (vs. RHE) for oxygen reduction reaction (ORR) and a small potential gap of 0.78 V between ORR and oxygen evolution reaction (OER) in 0.1 M KOH, which is one of the best to date among metal-free bifunctional electrocatalysts. Both zinc-air batteries using liquid electrolytes and the all-solid-state batteries assembled with such air cathodes exhibit excellent cycle performance and reversibility, which can be expressly observed by in-situ X-ray diffraction (XRD) characterization. This nitrogen dopants engineering strategy gives an effective methodology to make full use of nanocarbon materials for their practical applications in next-generation powerful and durable energy devices.

High‐Performance Platinum‐Perovskite Composite Bifunctional Oxygen Electrocatalyst for Rechargeable Zn–Air Battery

AbstractConstructing highly active electrocatalysts with superior stability at low cost is a must, and vital for the large‐scale application of rechargeable Zn–air batteries. Herein, a series of bifunctional composites with excellent electrochemical activity and durability based on platinum with the perovskite Sr(Co0.8Fe0.2)0.95P0.05O3−δ (SCFP) are synthesized via a facile but effective strategy. The optimal sample Pt‐SCFP/C‐12 exhibits outstanding bifunctional activity for the oxygen reduction reaction and oxygen evolution reaction with a potential difference of 0.73 V. Remarkably, the Zn–air battery based on this catalyst shows an initial discharge and charge potential of 1.25 and 2.02 V at 5 mA cm−2, accompanied by an excellent cycling stability. X‐ray photoelectron spectroscopy, X‐ray absorption near‐edge structure, and extended X‐ray absorption fine structure experiments demonstrate that the superior performance is due to the strong electronic interaction between Pt and SCFP that arises as a result of the rapid electron transfer via the PtOCo bonds as well as the higher concentration of surface oxygen vacancies. Meanwhile, the spillover effect between Pt and SCFP also can increase more active sites via lowering energy barrier and change the rate‐determining step on the catalysts surface. Undoubtedly, this work provides an efficient approach for developing low‐cost and highly active catalysts for wider application of electrochemical energy devices.

Rich diversity of crystallographic phase formation in 2D RexMo1 – xS2 (x < 0.5) alloy

We report on the observation of the rich variety of crystallographic phase formation in a RexMo1 – xS2 alloy for x < 0.5. For x < 0.23, no low dimensional superstructural modulation is observed and inter cation hybridization remains discrete, forming dimers to tetramers with increasing Re concentration. For x > 0.23, superstructural modulation is observed. Depending on the Re concentrations (x = 0.23, 0.32, 0.38, and 0.45) and its distributions, various types of cation hybridization result in the rich variety of low dimensional superstructural modulation as directly revealed by high resolution transmission electron microscopy. These layered alloy systems may be useful for various energy and novel device applications.

Near-Field Electrospinning for Three-Dimensional Stacked Nanoarchitectures with High Aspect Ratios.

Near-field electrospinning (NFES) was developed to overcome the intrinsic instability of traditional electrospinning processes and to facilitate the controllable deposition of nanofibers under a reduced electric field. This technique offers a straightforward and versatile method for the precision patterning of two-dimensional (2D) nanofibers. However, three-dimensional (3D) stacked structures built by NFES have been limited to either micron-scale sizes or special shapes. Herein, we report on a direct-write 3D NFES technique to construct self-aligned, template-free, 3D stacked nanoarchitectures by simply adding salt to the polymer solution. Numerical simulations suggested that the electric field could be tuned to achieve self-aligned nanofibers by adjusting the conductivity of the polymer solution. This was confirmed experimentally by using poly(ethylene oxide) (PEO) solutions containing 0.1-1.0 wt% NaCl. Using 0.1 wt% NaCl, nanowalls with a maximum of 80 layers could be built with a width of 92 ± 3 nm, height of 6.6 ± 0.1 μm, and aspect ratio (height/width) of 72. We demonstrate the 3D printing of nanoskyscrapers with various designs, such as curved "nanowall arrays", nano "jungle gyms," and "nanobridges". Further, we present an application of the 3D stacked nanofiber arrays by preparing transparent and flexible polydimethylsiloxane films embedded with Ag-sputtered nanowalls as 3D nanoelectrodes. The conductivity of the nanoelectrodes can be precisely tuned by adjusting the number of 3D printed layers, without sacrificing transmittance (98.5%). The current NFES approach provides a simple, reliable route to build 3D stacked nanoarchitectures with high-aspect ratios for potential application in smart materials, energy devices, and biomedical applications.

Highly-defective Fe-N-C catalysts towards pH-Universal oxygen reduction reaction

The defect engineering of nonprecious metal catalysts (NPMCs) is of significance to advance the oxygen reduction reaction (ORR) catalysts for the application of electrochemical energy devices. Herein, a facile H2O2-etching strategy is proposed to design Fe and N co-doped carbon catalysts (Fe-N-C/H2O2). Thanks to the etching of C, the defective carbon (DC) is endowed with robust anchoring ability, which is conducive to the modulation of active sites and microstructures, and further improvement of their ORR performances. Due to the supporting effect, the effective 3D nanostructures can be constructed. Integrated with the composition and morphology features, the resultant Fe-N-C/H2O2 achieves remarkable ORR performance with onset potential of 0.93 V and super stability with a subtle negative shift of 13.1 mV after 20 000 cycles in 0.1 M HClO4. Meanwhile, superior ORR performances are also revealed in alkaline and neutral electrolytes. This work provides an effective strategy for the design of advanced electrocatalysts towards fuel cells.

Development of a SnS Film Process for Energy Device Applications

Tin monosulfide (SnS) is a promising p-type semiconductor material for energy devices. To realize the device application of SnS, studies on process improvement and film characteristics of SnS is needed. Thus, we developed a new film process using atomic layer deposition (ALD) to produce SnS films with high quality and various film characteristics. First, a process for obtaining a thick SnS film was studied. An amorphous SnS2 (a-SnS2) film with a high growth rate was deposited by ALD, and a thick SnS film was obtained using phase transition of a-SnS2 film by vacuum annealing. Subsequently, we investigated the effect of seed layer on formation of SnS film to verify the applicability of SnS to various devices. Separately deposited crystalline SnS and SnS2 thin films were used as seed layer. The SnS film with a SnS seed showed small grain size and high film density from the low surface energy of the SnS seed. In the case of the SnS film using a SnS2 seed, volume expansion occurred by vertically grown SnS grains due to a lattice mismatch with the SnS2 seed. The obtained SnS film using the SnS2 seed exhibited a large reactive site suitable for ion exchange.