Maximum Output Power Density Research Articles

3D-Printed Flexible PVDF-TrFE Composites with Aligned BCZT Nanowires and Interdigital Electrodes for Piezoelectric Nanogenerator Applications

Piezoelectric nanogenerators based on piezoelectric nanocomposites have attracted much interest in recent decades owing to their excellent piezoelectric properties and application in self-powered systems and wearable sensors. As a promising piezoelectric ceramic filler in composite-based generators, one-dimensional (1D) piezoelectric nanowires were filled into a polymer matrix to enhance its dielectric and piezoelectric properties. In this paper, flexible PVDF-TrFE composite films containing highly aligned Ba0.85Ca0.15Ti0.9Zr0.1O3 (BCZT) nanowires (NWs) have been manufactured via a direct-ink writing method. The effect of BCZT NW content on the dielectric, ferroelectric, and piezoelectric properties was investigated using multiphysics modeling and detailed experiments. An optimum composite composition was discovered, and the piezoelectric composite film with 15 wt % BCZT NWs possessed the highest energy harvesting figure of merit of 5.3 × 10–12 m2/N. Interdigital electrodes were combined with the composite to fabricate a patterned piezoelectric nanogenerator, where the piezoelectric nanogenerator can produce an open-circuit output voltage of 17 V, and the maximum output power density could reach 5.6 μW/cm2. This work provides opportunities for the optimization and fabrication of piezoelectric materials for energy-harvesting and sensing applications.

Self-healable polymer complex with a giant ionic thermoelectric effect

In this study, we develop a stretchable/self-healable polymer, PEDOT:PAAMPSA:PA, with remarkably high ionic thermoelectric (iTE) properties: an ionic figure-of-merit of 12.3 at 70% relative humidity (RH). The iTE properties of PEDOT:PAAMPSA:PA are optimized by controlling the ion carrier concentration, ion diffusion coefficient, and Eastman entropy, and high stretchability and self-healing ability are achieved based on the dynamic interactions between the components. Moreover, the iTE properties are retained under repeated mechanical stress (30 cycles of self-healing and 50 cycles of stretching). An ionic thermoelectric capacitor (ITEC) device using PEDOT:PAAMPSA:PA achieves a maximum power output and energy density of 4.59 μW‧m−2 and 1.95 mJ‧m−2, respectively, at a load resistance of 10 KΩ, and a 9-pair ITEC module produces a voltage output of 0.37 V‧K−1 with a maximum power output of 0.21 μW‧m−2 and energy density of 0.35 mJ‧m−2 at 80% RH, demonstrating the potential for a self-powering source.

Effect of ZnO on the intermediate-temperature electrochemical properties of Gd0.1Ln0.1Ce0.8O2-α (Ln = Er, Yb) for solid oxide membrane fuel cells

In this study, Gd0.1Ln0.1Ce0.8O2-α (Ln = Er, Yb) was prepared by a glycine-nitrate combustion method. The influences of the calcining temperature, codoped ion and addition of sintering additive on the structures, grain sizes and intermediate-temperature electrochemical properties of the samples were investigated. The micromorphologies and crystal structures of the synthesized samples were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The relationship between the conductivity and oxygen partial pressure and the H2/O2 fuel cell was also studied. The XRD results showed that the samples were single-phase cubic fluorite structures after being calcined at 1350 °C and 1450 °C. The sintering additive of ZnO can significantly affect the morphology and density of the obtained ceria electrolytes. The conductivities of 1350-GEDC-ZnO and 1350-GYDC-ZnO reached 4.4 × 10−2 S cm−1 and 3.4 × 10−2 S cm−1 at 750 °C, respectively. The output performance of the intermediate-temperature thin film fuel cell was also studied by applying the electrolyte with the best electrical property. The maximum output power densities of the 1350-GEDC-ZnO membrane (15 μm) using Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) as the cathode were 296.2 mW cm−2, 406.2 mW cm−2 and 529.1 mW cm−2 at 650 °C, 700 °C and 750 °C, respectively.

Physiological and transcriptional studies reveal Cr(VI) reduction mechanisms in the exoelectrogen Cellulomonas fimi Clb-11.

A facultative exoelectrogen, Cellulomonas fimi strain Clb-11, was isolated from polluted river water. This strain could generate electricity in microbial fuel cells (MFCs) with carboxymethyl cellulose (CMC) as the carbon source, and the maximum output power density was 12.17 ± 2.74 mW·m-2. In addition, Clb-11 could secrete extracellular chromate reductase or extracellular electron mediator to reduce Cr(VI) to Cr(III). When the Cr(VI) concentration was less than 0.5 mM in Luria-Bertani (LB) medium, Cr(VI) could be completely reduced by Clb-11. However, the Clb-11 cells swelled significantly in the presence of Cr(VI). We employed transcriptome sequencing analysis to identify genes involved in different Cr(VI) stress responses in Clb-11. The results indicate that 99 genes were continuously upregulated while 78 genes were continuously downregulated as the Cr(VI) concentration increased in the growth medium. These genes were mostly associated with DNA replication and repair, biosynthesis of secondary metabolites, ABC transporters, amino sugar and nucleotide sugar metabolism, and carbon metabolism. The swelling of Clb-11 cells might have been related to the upregulation of the genes atoB, INO1, dhaM, dhal, dhak, and bccA, which encode acetyl-CoA C-acetyltransferase, myo-inositol-1-phosphate synthase, phosphoenolpyruvate-glycerone phosphotransferase, and acetyl-CoA/propionyl-CoA carboxylase, respectively. Interestingly, the genes cydA and cydB related to electron transport were continuously downregulated as the Cr(VI) concentration increased. Our results provide clues to the molecular mechanism of Cr(VI) reduction by microorganisms in MFCs systems.

Bio‐Physicochemical Dual Energy Harvesting Fabrics for Self‐Sustainable Smart Electronic Suits

AbstractDespite the rapid development of various wearable generators to harvest energy from human activity, they are limited to single or intermittent power generation. Here, stretchable and washable energy harvesting fabric is reported, which enables biomechanical and biochemical generation through co‐weaving triboelectric generator (TEG) and perspiration electric generator (PEG)‐based fibers. The two energy harvesting approaches can work individually or simultaneously, thereby combating humidity and increasing the electrical output. The maximum output power density of TEG‐ and PEG‐based fibers can achieve 166 and 5.4 µW cm−2, respectively. The woven‐structured patch‐type energy harvester is conformable with clothing. It can harvest energy from human movements and sweat to drive the wearable Internet of Things (IoT) without charging systems. This synergistic and complementary energy harvester can provide a viable standalone power source relying solely on human activity for wearable electronics.

Surface Textured Double Layer Triboelectric Nanogenerator for Autonomous and Ultra‐Sensitive Biomedical Sensing

AbstractTriboelectric nanogenerators (TENGs) have demonstrated great promise especially for the realization of self‐powered biomedical sensors. Nevertheless, developing TENG sensors able to detect the broad range of biomechanical movements experienced on the human body is still a challenge. Herein, a unique ridge‐structured device sensitive to wide range of forces is reported (i.e., low‐forced pulse monitoring to high‐forced gait monitoring). The device is composed of thermoplastic polyurethane layer sandwiched between two textured silicon elastomeric layers. Compared to non‐textured surface configurations, the proposed ridged‐structure provides an increased frictional contact area between the triboelectric materials, while also acting as a spacer between the triboelectric materials. The influence of ridge dimensions on the output performance is investigated by mechanical simulations and electromechanical experimental tests. The optimized device shows a maximum peak output power and current densities of 490 mW m−2 and 1750 µA m−2, respectively at 30 N and 7 Hz of compressive forces. The proposed device exhibits stable electrical output for 10000 cycles. As a proof of concept, the proposed device is used as wearable sensors for monitoring pulse rate, breath patterns, and gait movements. The study suggests the possibility of utilization of novel‐structured sandwich‐type elastomer ridge‐based TENG in different aspects of biomedical sensing and smart wearable application.

Optimal Design of Wearable Micro Thermoelectric Generator Working in a Height-Confined Space

With the increasing development of self-powered wearable electronic devices, there is a growing interest in thermoelectric generators (TEGs). To achieve more comprehensive and reliable functionality of wearable devices, improving the power generation performance of thermoelectric devices will be the key. It has been shown that integrating a heat sink at the cold end of the TEG increases the effective temperature difference and, thus, maximizes the power output of the thermoelectric device. However, the space left for the power supply is often limited. How to optimize the integrated system of micro-thermoelectric generators and heat sinks in a height-confined space has become the key. In this study, we have established a corresponding model using a numerical calculation method, systematically studied the influence of TEG geometric size on the number of fins and fin height, and determined the optimal number of fins for the highest equivalent convective heat transfer coefficient corresponding to different fin heights. We also conducted the co-design of TEG and fin topological structure to study the effects of the ratio of leg height to fin height (l/H), the width of legs (w), and the number of thermoelectric leg pairs (N) on the maximum output power density per unit area (Pm1) and the maximum output power density per unit mass (Pm2) of the device. When N = 16, w = 0.3 mm, l/H = 2.5 (that is, l = 3.57 mm, H = 1.43 mm), and Pm1 reaches the maximum value of 30.5 μW/cm2; When N = 2, l/H = 0.25 and w = 0.3 mm, and Pm2 reaches a maximum value of 5.12 mW/g. The measured values of the open-circuit voltages of fabricated micro-TEGs with different thermoelectric leg heights (l = 0.49 mm, l = 1.38 mm, and l = 1.88 mm) are basically consistent with the simulated values. When N = 2, l = 0.49 mm, H = 3.74 mm, and w = 0.85 mm, and Pm2 reaches 0.44 mW/g. The results provide insights into the optimal design of wearable micro thermoelectric generator working in a height-confined space and highlight the importance of co-designing TEGs and fin topological structures for optimizing their performance.

Ultrafast and Cost-Effective Fabrication of High-Performance Carbon-Based Flexible Thermoelectric Hybrid Films and Their Devices.

Due to their cost-effectiveness and industry-scale feasibility, carbon-based composites have been considered to be promising thermoelectric materials for low-grade power generation. However, current fabrications for carbon-based composites are time-consuming, and their thermoelectric properties are still low. Herein, we develop an ultrafast and cost-effective hot-pressing method to fabricate a novel carbon-based hybrid film, which consists of ionic liquid/phenolic resin/carbon fiber/expanded graphite. This method only costs no more than 15 min. We found that the expanded graphite as the major component enables high flexibility and the introduction of phenolic resin and carbon fiber enhances the shear resistance and toughness of the film, while the ion-induced carrier migration contributes to a high power factor of 38.7 μW m-1 K-2 at 500 K in the carbon-based hybrid film. After the comparison based on the ratios between the power factor with fabrication time and cost among the current conventional carbon-based thermoelectric composites, our hybrid films show the best cost-effective property. Besides, a flexible thermoelectric device, assembled by the as-designed hybrid films, shows a maximum output power density of 79.3 nW cm-2 at a temperature difference of 20 K. This work paves a new way to fabricate cost-effective and high-performance carbon-based thermoelectric hybrids with promising application potential.

Parallel arrays of clay nanosheets sandwiched in two-dimensional nanofluidic membrane for enhanced ion transport properties

High ion selectivity and high structural stability have always been the pursuit of nanofluidic ion exchange membranes but they are often trade-offs. Herein, we built a sandwich structure by introducing parallel arrays of clay nanosheets in two-dimensional nanofluidic membrane to improve the ion transport performance. The introduction of an appropriate amount of clay nanosheets can not only redistributes internal stress and thereby increases the tensile strength but also provides higher surface charge density and thereby effectively increases ion selectivity of the membrane. The current density obtained from the sandwich structure membrane is ∼5 times than that of the homogeneous membrane and the cation mobility can reach a maximum of 0.98. When simulating the energy conversion of seawater and river water, the maximum output power density achieved through the membrane is 0.70 W m−2, which is increased by ∼6 times. Interestingly, it significantly weakens the internal resistance from 100 to 30 kΩ and the energy barriers from 4.56 to 2.13 kJ mol−1 of ion permeation in the entire regime although the clay nanosheets arrays increases the thickness of the membrane. This strategy of introducing negatively charged nanosheets of natural minerals to enhance ion transport properties provides a new idea for the enhancement and application of salinity gradient energy harvesting membranes.

Trace N-doped manganese dioxide cooperated with Ping-pong chrysanthemum-like NiAl-layered double hydroxide on cathode for improving bioelectrochemical performance of microbial fuel cell

Trace N-doped manganese dioxide (MnO2) nanoparticles were attached to NiAl-layered double hydroxide (LDH) nano sheets by a simple two-step hydrothermal reaction, and N-MnO2@NiAl-LDH was successfully prepared as cathode catalyst of microbial fuel cell (MFC). N-MnO2@NiAl-LDH was Ping-pong chrysanthemum-like structure formed by overlapping lamellar structures, with spherical MnO2 particles attached on. The unique Ping-pong chrysanthemum-like structure and pore size distribution provided large number of electrochemical active sites. The recombination of trace N and MnO2 reduced the charge transfer resistance, accelerated the electron transfer rate, and N-MnO2@NiAl-LDH showed high oxygen reduction reaction (ORR) capability. The maximum output power density of N-MnO2@NiAl-LDH-MFC was 698 mW/m2, about 4.59 times of NiAl-LDH (152.1 mW/m2). The maximum voltage was about 320 mV, and the stability was good for about 7 d. This would provide technical reference for the utilization of cathode catalyst for fuel cells.

Enhancing the output of triboelectric nanogenerator by embedding SrTiO3 nanoparticles into polydimethylsiloxane films

To improve the output power of polydimethylsiloxane (PDMS)-based triboelectric nanogenerators (TENGs), SrTiO3 (STO), which is a high-k material, nanoparticles (NPs) was embedded into the PDMS films because the relative permittivity of triboelectric films is proportional to the output power. The STO NPs/PDMS composite films showed a maximum output power density of approximately 3.6 W m−2 at the content of the STO NPs of 20 vol%. To further boost the output power, we measured the output power at a contact/separation tapping frequency of 5 Hz. The maximum output power density was approximately 32.4 W m−2. This method is expected to be applicable to various material combinations for TENGs.

Theoretical prediction of time-related performance of GaN-based p–n junction betavoltaic battery

Betavoltaic batteries can meet long-term energy supply needs. However, due to the decay of the radioactive source, the output performance of battery will change over time, and the laws of this change require elucidation to aid the battery engineer. In this study, the influences of time on the apparent power density and β-energy spectrum of the 63 Ni source were clarified. Moreover, the structural parameters, including the p-region, n-region doping concentrations, and junction depth of GaN-based (hexagonal) p–n junction, were optimized, which are 2 × 1017 cm–3, 1014 cm–3, and 0.1 μm, respectively. In particular, the time-related performance trends were analyzed, and a formula for the maximum output power density deterioration was obtained, which can be used to evaluate the performance of 63 Ni GaN-based p–n junction betavoltaic battery within 200 years. The simulation results showed that the maximum output power density of battery after 50 years is 0.243 μW cm−2, which is only 60% of the initial value. In addition, the other output performances, namely, the short-circuit current density, open-circuit voltage, fill factor, and conversion efficiency are 0.096 μA cm−2, 2.67 V, 94.3%, and 20.5%, respectively.

More than the interface: Synergistic engineering of the interfacial and its subjacent layers followed by self-triggering for high efficient bioelectricity harvesting

The practical application of microbial fuel cell (MFC) is severely impeded by its low output power density stemming from the low bacterial loadings and the sluggish extracellular electron transfer (EET) kinetics. Thus, the current collector designed to greatly enhance the electrocatalytic performance of microbial electrodes ought to possess both high hydrophilicity and high conductivity, which are, however, often mutually incompatible. Herein, to resolve this dilemma, a composite bioelectrode consisting of the poly(ionic liquid) functionalized single-walled carbon nanotube bundles (SWCNT-PIL) layer at the biotic-electrode interface and its subjacent hydrophilic graphene oxides (GO) layer is prepared. Bacterial adhesion is significantly enhanced, resulting from the positive charges of SWCNT-PIL and the hydrophilic GO. After self-reduction of GO by attached electricigens, the as-prepared mrGSP bioelectrode exhibits a maximum output power density of 4.808 W m−2, which is more than one order of magnitude larger than that of conventional carbon-based electrode (0.319 W m−2), because the SWCNT-PIL layer is capable of not only accelerating the flavin-based mediated electron transfer (MET), but also upregulating the membrane protein expression from 14.64% to 18.01% induced by the enhanced electric field, promoting the outer membrane c-type cytochromes-based direct electron transfer (DET). This work provides a new concept of synergistic engineering the interfacial and its subjacent layers to solve the dilemma between high hydrophilicity and high conductivity of the current collector surface for microbial electrocatalysis.

Theoretical analysis of betavoltaic cells based on pDSBD structure

Based on the interaction between β particles and matter and the physical properties of semiconductor devices, the Monte Carlo method was used to simulate the self-absorption effect of β radiation sources and their transport process in different metal/diamond devices. A theoretical calculation model of a p-diamond Schottky barrier diode (pDSBD) betavoltaic cell using an isotropic cuboid source (63Ni) is proposed. The results show that the optimal thickness of the 63Ni radiation source is 2 µm. For the metal materials Al, Au, Cu, Ni and Pt used in the preparation of Schottky contacts, the metal work function significantly affects the output of the pDSBD cells. Among them, the maximum output power density, filling factor, energy conversion efficiency and total energy conversion efficiency of the Al/pDSBD cell are 0.224 µW/cm2, 0.933, 14.53% and 2.06%, respectively.

A two-stage sodium converter coupled to a two-stage TEG: Parametric optimization

The aim of this study is to deeply study and analysis of energetic performance of the novel coupled system composed of a two-stage sodium thermal electrochemical converter and a two-stage thermoelectric generator. The main methods are to establish the model of the coupling system by considering the main irreversibilities, and obtain the analytical expressions of the power outputs and efficiencies of two subsystems and coupling system. The main novelties are to obtain the optimum ranges of critical parameters of the coupled system and give the reasonably matching conditions between the subsystems. The main contents of this study include that the influences of the intermediate and condenser temperatures of the sodium thermal electrochemical converter and current density of the first stage sodium thermal electrochemical converter as well as the electric current of the two-stage thermoelectric generator on the efficiency and power output density are discussed and the maximum power output density and efficiency of the system are calculated and compared with those of the single two-stage sodium thermal electrochemical converter and the existing coupling models. Results show that the maximum efficiency and maximum power output density of the coupled system attain 0.413 and 68.7×103 W m−2 and exhibit an improvement of about 14.1% and 66.7% than those of the standalone two-stage sodium thermal electrochemical converter respectively, and the maximum efficiency of the whole system increase 37.7% compared with that of the existing coupling system. The results obtained indicate that the performance of the proposed system is greatly improved by efficient the exhaust heat utilization. In addition, the multi-objective and multi-parametric optimization analyses are adopted to search for the global optimization profile and validate the obtained findings.

Investigation on Thermal and Electrical Performance of Late-Model Plate-and-Tube in Water-Based PVT-PCM Collectors

A large amount of redundant energy gained from incident solar energy is dissipated into the environment in the form of low-grade heat, which significantly reduces and limits the performance of photovoltaic cells, so removing or storing redundant heat and converting it back into available thermal energy is a promising way to improve the utilization of solar energy. A new combined water-based solar photovoltaic-thermophotovoltaic system embedded in the phase change material (PCM) mainly is proposed and designed. The effects of the water flow rate, cell operating temperature, the presence of PCM, and the thickness of the PCM factor on the overall module performance are explored comprehensively. The maximum thermal power output and the corresponding efficiency of the combined-system-embedded PCM are calculated numerically, The results obtained are compared with those of the PV (photovoltaic) and PVT(photovoltaic-thermal) cells with the same solar operating conditions. In addition, the PVT-PCM system possesses a higher power output and overall efficiency in comparison with the PVT and PV system, and the maximum cell temperature reduction of 12.54 °C and 42.28 °C is observed compared with PVT and PV systems. Moreover, an increased average power of 1.13 W and 4.59 in PVT-PCM systems is obtained compared with the PVT system and the PV system. Numerical calculation results illustrate that the maximum power output density and efficiency of the PVT-PCM are 3.06% and 16.15% greater than those of a single PVT system and PV system in the working time range, respectively. The obtained findings show the effectiveness of using PCM to improve power output and overall efficiency.

Performance investigation and comparison of polypropylene to Nafion117 as the membrane of a dual-chamber microbial fuel cell

The high cost and recycling issues of common separators as the main components of Microbial fuel cells (MFCs) have slowed down the development of MFCs recently. In this paper, a polypropylene membrane is proposed as an inexpensive membrane that can be recycled with lower environmental impacts. An experiment is performed in a dual-chamber microbial fuel cell to investigate and compare the proposed membrane effectiveness to Nafion117. The dual-chamber MFC was used because of its ease of use. A mixture of microbes and glucose was fed to the cell during the experiment. The internal resistance and coulombic efficiency are calculated by measuring the circuit voltage, power density, and open-circuit voltage to monitor the performance. The maximum output voltage of 500 mV was attained at a resistance of 380 kΩ. Furthermore, the maximum output power density was 0.7 mW.m−2, which occurred for 3.3 mA.m−2.

Magnetosensory Power Devices Based on AlGaN/GaN Heterojunctions for Interactive Electronics

AbstractThe advances in biological magnetoreception and microelectronics have promoted the vigorous development of interactive electronic devices capable of noncontact interaction and control via magnetic fields. Here, a magnetosensory power device (MPD) that integrates a magnetic film ((Fe90Co10)78Si12B10) unit into a cantilever‐structured AlGaN/GaN‐based high‐electron‐mobility‐transistor is presented. The MPD is capable to not only sense external magnetic field, but also control device output power with the emulation of magnetoreception. Specifically, the device can achieve significant control of output power density (18.04 to 18.94 W mm−2) quasi‐linearly with magnetic field stimuli (0–400 mT) at a gate bias of −5 V. In addition, the maximum output power density of the MPD can reach 85.8 W mm−2 when a gate bias of 1 V is applied. The simulation and experimental results show that MPD has excellent orientation and magnetic field sensing functions under 0–400 mT magnetic fields. With the intelligent capabilities of magnetic sense and output power control, such interactive electronic devices will have broad application prospects in the fields of artificial intelligence, advanced robotics, and human‐machine interfaces.

A hybrid nanogenerator for collecting both water wave and steam evaporation energy

Water is an important resource for building different energy systems towards diversified applications. In this paper, a novel hybrid nanogenerator is proposed based on a water-wave triboelectric nanogenerator (TENG) and evaporation generator, which opens up a more effective approach to fully utilize the energy from water. This hybrid nanogenerator can solve the problem of insufficient output of water wave TENGs in calm water. The optimized peak power of water-wave TENG can reach 0.62 mW under simulated waves frequency of 2.5 Hz, while a capacitor of 0.33 µF can be charged to 15 V by TENG within 80 s in actual water waves. The evaporation generator based on wood block can continuously generate direct currents during the spontaneous evaporation of water. The solar-vapor conversion efficiency of evaporation generator can reach 84.2%, while the evaporation generator can provide a maximum current density of 3.2 μA·cm−2 and a maximum output power density of 1.4 mW·m−2 with a matching load of 10 kΩ (23 ℃, 30% RH). To demonstrate the application capability of the evaporation generator, we design a multi-stage boost circuit coupled with the pulse charging method, which can increase the voltage output and effectively reduce the charging time. The proposed hybrid nanogenerator provides a promising way for collecting both water wave and steam evaporation energy, effectively broadening methods for energy harvesting by TENGs.

Monodomain liquid crystal elastomer bionic muscle fibers with excellent mechanical and actuation properties

Monodomain liquid crystal elastomers (m-LCEs) exhibit large reversible deformations when subjected to light and heat stimuli. Herein, we developed a new method for the large-scale continuous preparation of m-LCE fibers. These m-LCE fibers exhibit a reversible contraction ratio of 55.6%, breaking strength of 162MPa (withstanding a load of 1 million times its weight), and maximum output power density of 1250J/kg, surpassing those of previously reported m-LCEs. These excellent mechanical properties are mainly attributed to the formation of a homogeneous molecular network. Furthermore, the fabrication of m-LCEs with permanent plasticity using m-LCEs with impermanent instability without external intervention was realized by the synergistic effects of the self-restraint of mesogens and the prolonged relaxation process of LCEs. The designed LCE fibers, which are similar to biological muscle fibers and can be easily integrated, exhibit broad application prospects in artificial muscles, soft robots, and micromechanical systems.