查看更多>>摘要：Flexible devices operated at a cryogenic temperature are required for significant applications, such as sensors in thermal imaging and infrared and nuclear particle detectors. Hence, in this study, comprehensive temperature dependence was performed on flexible GaN thin films from 225 K to 325 K under 0.0-0.3% strains to investigate the piezotronic and piezophototronic effects. The GaN thin-film device strongly depends on the applied temperature, and the piezotronic effect is enriched by above 360% under 0.3% applied strain at a low chamber temperature. This type of behavior is caused by the increased essential piezocharges at the interface/surface, which results from the less screening effect of the reduced charge carriers in the GaN thin film. To support this behavior, we investigate the piezophototronic effect in a GaN thin film at various temperatures under different strains. The study results will provide an in-depth understanding of the piezotronic and piezo-photonic effects and pave the way for forthcoming device applications in various fields, including human-machine interface, health monitoring, artificial intelligence, and surgical robotic operations.
查看更多>>摘要：Electrocatalytic CO2 reduction to value-added chemicals is of great potential in maintaining carbon balance and alleviating energy shortage. Stabilizing and accelerating the formation of *OCHO intermediate is the key to achieve high-selectivity formate production. Herein, Bi nanoparticles embedded in pyrrolic-N-dominated doped carbon nanosheets (similar to 10 nm) (PNCB) delivered a maximum formate selectivity of 94.8% (-1.05 V) and a partial current density of - 22 mA cm(-2) in H-type electrolyzers. According to theoretical calculation results, the critical pyrrolic-N doping in carbon nanosheets promoted electron transfer from N to Bi atoms, which facilitates stabilizing *OCHO intermediate and boosting formate formation. The rechargeable Zn-CO2 batteries applying PNCB as anode catalysts displayed the maximum power density of 1.43 mW cm(-2) with CO emission below 11%. For coupled CO2 reduction (catalyzed by PNCB) and oxygen evolution (catalyzed by 10 wt% Ir/C), a large current density up to 180 mA cm(-2) in flow cells was also achieved. This work provides an effective strategy to regulate the support components and electron accumulation towards electrocatalytic CO2 reduction to formate as well as related clean energy devices.
查看更多>>摘要：By introducing phenylethylammonium cation (PEA(+)) as steric hindrance, the two-dimensional (2D) Ruddlesden- Popper (RP) (PEA)(2)(Cs)(n-1)PbnI3n+1 (n <= 5) exhibits much stronger phase stability than 3D CsPbI3 . However, uncontrollable crystallization process leads to poor coverage and unfavorable phase management in the final (PEA)(2)(Cs)(n-1)PbnI3n+1 film, resulting in low power conversion efficiency (PCE < 10%) and poor stability of the related perovskite solar cells (PSCs). Here, we propose an underlying surface engineering (USE) method, which improves the wettability of the substrate and promotes the diffusion of the precursor solution to fabricate a highquality film with high coverage and low defect density. Further characterizations confirm that this method enables a more uniform phase distribution and achieves an orderly arrangement of small-n and large-n phases from bottom to surface in film, which contributes to effective charge transfer to enhance photocurrent transmission and extraction. As a result, the PCE of (PEA)(2)(Cs)(n-1)PbnI3n+1 PSCs was boosted from initial 9.03% to a record value of 15.92%, accompanied by enhanced stability. Encouragingly, this method also has versatility in other RP and Dion-Jacobson (DJ) types of 2D CsPbI3 PSCs, paving a broad road for its commercial application in the future.
查看更多>>摘要：A novel textile-based triboelectric nanogenerator (TENG) with woven structure operating in freestanding triboelectric-layer mode, defined as a woven-TENG, has been developed. Whereas most woven-structured TENGs operate in contact-separation mode and consist of one type of triboelectric material, this woven-TENG comprises woven electrodes and woven strips of positive and negative triboelectric material, which form a checker-like pattern over the electrodes with matching periodicity. The implementation of the positive and negative triboelectric material significantly improves the performance of the woven-TENG. Furthermore, in contrast to the conventional grating-structured and woven-structured TENG, which are designed to operate only in one moving direction, this new design also allows the woven-TENG to harvest energy from all-planar directions of movement. The woven-TENG with woven strips of nylon and polytetrafluoroethylenevinyl (PTFE) fabric can generate a root mean square (RMS) open-circuit voltage of 62.9 V, an RMS short-circuit current of 1.77 mu A and a maximum RMS power of 34.8 mu W at a load resistance of 50 M ohm, a mechanical oscillation of 2 Hz and a contact force of 5 N. This corresponds to a maximum RMS power density of 5.43 mW/m2.
查看更多>>摘要：Flexible and wearable electronics have presented a wide range of advantages to non-invasive real-time human health monitoring. However, its remarkable energy consumption during continuous and long-time operation brings essential, practical challenges, which lead to growing recognition of exploring new and efficient energy strategies for wearables. Here, inspired by human joints as a biomechanical energy source that shows an ideal option for sustainable powers, we design a battery-free sweat sensing system integrated with sweat resistant selfsustainable energy supply and wireless communication interface, where piezoelectric nanogenerators (PENGs) efficiently converting biomechanical energy from freely movable joints (finger, cubital fossa and popliteal space) into electricity serving as the self-powering module. Physiological relevant parameters in sweat, including Na+ , K+ and pH, are sensed and wirelessly transmitted to the user interface via Bluetooth communication. This system shows a paradigm of wearable electronics driven by human joints that demonstrated efficient self-sustainable energy supply and multiplexed physiological detection.
查看更多>>摘要：Triboelectric nanogenerator (TENG) is a new category of efficient technologies for energy harvesting applications. It has been shown as a promising method for converting low-frequency mechanical motions into electrical energy. The amount of power generated and its optimization are the most important criteria in the design of TENGs. However, some important factors influencing the performance of TENGs are not well known. Here, the TENG inherent capacitance optimization was fully studied, and its impact on the output performance of the energy harvester was assessed. The inherent capacitance of most TENGs varies over time, limiting effective power transfer to the electrical load. Thus, an optimal series capacitor was incorporated into the TENG to stabilize the variations in its inherent capacitance and improve power generation performance. Moreover, this study theoretically demonstrated that this solution increases the system figure of merit, which defines the peak output power in a single cycle. With the addition of the optimal series capacitor into the TENG, the stored energy in a 1000 mu F capacitor was increased up to 82.36%. According to the experiments, using a modified power management circuit can dramatically boost the harvested power. Compared to the direct usage of TENG without any interface circuit, using the proposed capacitance optimization method and modification of the power management circuit multiplied the stored energy in a 1000 mu F capacitor by 173.9 times. The findings of this study highlight the importance of optimizing the inherent capacitance of the TENG as well as the load resistance, which has important implications for the optimization of TENGs. This method is expected to broaden the applications of TENG devices.
查看更多>>摘要：Lithium metal batteries (LMBs) have great potential for next-generation rechargeable batteries due to the high theoretical capacity and ideal compatibility coupled with diverse cathode materials. However, the random Li deposition associated with the large local space charge caused by the anion depletion near the surface of anode, as well as the insufficient reduction of Li+ related to the suppressed Li+ solvation process induced by the electrostatic force between anion and cation hinder the development of high-energy-density LMBs. Herein, as evidenced theoretically and experimentally, we simultaneously eliminate the anion depletion region and promote the lithium salt dissociation by employing ZIF-67 with unsaturated metal sites as anionphilic additive to regulate anion distribution and weaken its bond with Li+. As a result, the short-circuit hazard is remitted in symmetrical cell with modified electrolyte at 3 mA cm-2 under capacity of 3 mAh cm-2 for more than 2000 h. As employed for the lithium-sulfur battery with high sulfur loading of 4.5 mg cm-2, the modulated electrolyte enables the battery delivering an initial capacity of 713 mAh g- 1 with decay rate of 0.05% per cycle over 100 cycles at 3 mA cm-2. This work demonstrates an efficient and scalable strategy for constructing dendrite-free LMBs via eliminating the anion depletion region and facilitating the Li+ solvation process.
查看更多>>摘要：Flexible triboelectric nanogenerators (TENGs) are sustainable energy sources to power a diverse range of intelligent sensing and monitoring devices and poly(vinylidene fluoride) (PVDF) is a common polymer incorporated in TENGs. To further enhance the electrical outputs of PVDF based TENGs, herein we present a technique for introducing liquid metal (LM) Galinstan nanodroplets into electrospun PVDF-co-hexafluoropropylene (PVDFHFP) nanofibers to enhance their triboelectric performance. Using the PVDF-HFP/2%LM nanofiber membrane as the negative tribo-layer and thermoplastic polyurethane as the positive tribo-layer, the peak open-circuit voltage and power density of the resultant TENG reached 1680 V and 24 W/m2, respectively, which are significantly higher than previous state-of-art values of existing PVDF based TENGs. This outstanding performance is attributed to multiple factors, including the improved surface potential, capacitance, charge trapping capability, and the secondary polarization inside PVDF-HFP nanofiber by the introduced LM nanodroplets. With the mechanical properties of PVDF-HFP nanofiber membranes weakened slightly after the increase of the LM content, the PVDF-HFP incorporating 2% LM showed the highest multifunctionality efficiency of mechanical performance and electrical generation. The LM modified PVDF-HFP nanofiber membranes can be promising materials in high performance TENGs as the negative tribo-layer.
查看更多>>摘要：Effectively utilize photogenerated holes (h+) of catalysts while blocking rapid recombination of photoinduced carriers are the two critical challenges for solar-to-hydrogen (STH) conversion. Here, an exquisite 2D/2D LaVO4/ g-C3N4 (LaVO4/CN) heterostructure is delicately designed and fabricated for efficient photocatalytic H2-evolution while producing high value-added furfural simultaneously. The abundant biomass furfuryl alcohol (FFA) is employed to substitute the traditional h+ sacrificial agents such as triethanolamine (TEOA) for the oxidation half reaction, which is very meaningful to balance the H2-evolution half reaction. The LaVO4/CN heterojunction enables 3-time increased H2-evolution and a high furfural-production rate (0.95 mmol g-1 h-1) than that of pristine graphite carbon nitride (g-C3N4, labeled as CN), and with a 22.16% H2-evolution apparent quantum efficiency (AQE) irradiated at 400 nm. This work provides an exquisite catalyst and a new strategy for efficient photocatalytic H2-evolution coupled with production of high valuable chemicals.
查看更多>>摘要：Harvesting low-grade heat as source of electrical power has emerged as a research frontier for self-powered wearable devices, as a promising route to overcome challenges associated with limited access to grid power. However, such promise is compromised by current attainable thermopowers and constraints of rigid or complicated thermoelectric systems. We report an ultrahigh thermopower of 19.32 mV K-1 on a stretchable thermoelectric module by the assembly of porous electrodes and hybrid hydrogel, containing 1-ethyl-3-methylimidazolium and tetrafluoroborate ions and polyethylene glycol. The anions act as charge carrier; for the first time, distinct ion mobilities are directly measured by 2D-diffusion-ordered nuclear magnetic resonance spectroscopy. By regulating ion transport via the synergy of selective ion-localization and thermo-osmotic mechanism, such design provides an effective strategy to increase thermopower, and our device is endowed with high output power density, tailorable architecture, and excellent stretchability, which is showcased in a thermoelectric wristband for body heat recovery.
NSTL
Elsevier