Thermogalvanic cells offer a cheap, flexible and scalable route for directly converting heat into electricity. However, achieving a high output voltage and power performance simultaneously from ...low-grade thermal energy remains challenging. Here, we introduce strong chaotropic cations (guanidinium) and highly soluble amide derivatives (urea) into aqueous ferri/ferrocyanide (Fe(CN)
/Fe(CN)
) electrolytes to significantly boost their thermopowers. The corresponding Seebeck coefficient and temperature-insensitive power density simultaneously increase from 1.4 to 4.2 mV K
and from 0.4 to 1.1 mW K
m
, respectively. The results reveal that guanidinium and urea synergistically enlarge the entropy difference of the redox couple and significantly increase the Seebeck effect. As a demonstration, we design a prototype module that generates a high open-circuit voltage of 3.4 V at a small temperature difference of 18 K. This thermogalvanic cell system, which features high Seebeck coefficient and low cost, holds promise for the efficient harvest of low-grade thermal energy.
Solar-enabled steam generation has attracted increasing interest in recent years because of its potential applications in power generation, desalination, and wastewater treatment, among others. ...Recent studies have reported many strategies for promoting the efficiency of steam generation by employing absorbers based on carbon materials or plasmonic metal nanoparticles with well-defined pores. In this work, we report that natural wood can be utilized as an ideal solar absorber after a simple flame treatment. With ultrahigh solar absorbance (∼99%), low thermal conductivity (0.33 W m–1 K–1), and good hydrophilicity, the flame-treated wood can localize the solar heating at the evaporation surface and enable a solar-thermal efficiency of ∼72% under a solar intensity of 1 kW m–2, and it thus represents a renewable, scalable, low-cost, and robust material for solar steam applications.
Sodium-ion batteries are a potentially low-cost and safe alternative to the prevailing lithium-ion battery technology. However, it is a great challenge to achieve fast charging and high power density ...for most sodium-ion electrodes because of the sluggish sodiation kinetics. Here we demonstrate a high-capacity and high-rate sodium-ion anode based on ultrathin layered tin(II) sulfide nanostructures, in which a maximized extrinsic pseudocapacitance contribution is identified and verified by kinetics analysis. The graphene foam supported tin(II) sulfide nanoarray anode delivers a high reversible capacity of ∼1,100 mAh g(-1) at 30 mA g(-1) and ∼420 mAh g(-1) at 30 A g(-1), which even outperforms its lithium-ion storage performance. The surface-dominated redox reaction rendered by our tailored ultrathin tin(II) sulfide nanostructures may also work in other layered materials for high-performance sodium-ion storage.
Converting body heat into electricity is a promising strategy for supplying power to wearable electronics. To avoid the limitations of traditional solid‐state thermoelectric materials, such as ...frangibility and complex fabrication processes, we fabricated two types of thermogalvanic gel electrolytes with positive and negative thermo‐electrochemical Seebeck coefficients, respectively, which correspond to the n‐type and p‐type elements of a conventional thermoelectric generator. Such gel electrolytes exhibit not only moderate thermoelectric performance but also good mechanical properties. Based on these electrolytes, a flexible and wearable thermocell was designed with an output voltage approaching 1 V by utilizing body heat. This work may offer a new train of thought for the development of self‐powered wearable systems by harvesting low‐grade body heat.
A flexible and wearable integrated thermocell based on gel electrolytes was designed. Utilizing body heat, an output voltage of almost 1 V was achieved, offering a new train of thought for self‐powered wearable systems that harvest low‐grade waste heat.
A low-cost high-performance solid-state flexible asymmetric supercapacitor (ASC) with α-MnO2 nanowires and amorphous Fe2O3 nanotubes grown on flexible carbon fabric is first designed and fabricated. ...The assembled novel flexible ASC device with an extended operating voltage window of 1.6 V exhibits excellent performance such as a high energy density of 0.55 mWh/cm3 and good rate capability. The ASC devices can find numerous applications as effective power sources, such as powering color-switchable sun glasses and smart windows.
The direct printing of microscale quantum dot light‐emitting diodes (QLEDs) is a cost‐effective alternative to the placement of pre‐formed LEDs. The quality of printed QLEDs currently is limited by ...nonuniformities in droplet formation, wetting, and drying during inkjet printing. Here, optimal ink formulation which can suppress nonuniformities at the pixel and array levels is demonstrated. A solvent mixture is used to tune the ejected droplet size, ensure wetting, and provoke Marangoni flows that prevent coffee stain rings. Arrays of green QLED devices are printed at a resolution of 500 pixels in.−1 with a maximum luminance of ≈3000 cd m−2 and a peak current efficiency of 2.8 cd A−1. The resulting array quality is sufficient to print displays at state‐of‐the‐art resolutions.
High‐resolution functional quantum dot pixels for displaying can be realized by inkjet printing. The ink formulation is the vital factor, in order to tune droplet formation, wetting, and pixel drying. The underlying mechanisms are discussed separately and combined to enable high‐resolution devices.
Paper electronics offer an environmentally sustainable option for flexible and wearable systems and perfectly fit the available printing technologies for high manufacturing efficiency. As the heart ...of energy‐consuming devices, paper‐based batteries are required to be compatible with printing processes with high fidelity. Herein, hydrogel reinforced cellulose paper (HCP) is designed to serve as the separator and solid electrolyte for paper batteries. The HCP can sustain higher strain than pristine papers and are biodegradable in natural environment within four weeks. Zinc‐metal (Ni and Mn) batteries printed on the HCP present remarkable volumetric energy density of ≈26 mWh cm–3, and also demonstrate the feature of cuttability and compatibility with flexible circuits and devices. As a result, self‐powered electronic system could be constructed by integrating printed paper batteries with solar cells and light‐emitting diodes. The result highlights the feasibility of hydrogel reinforced paper for ubiquitous flexible and eco‐friendly electronics.
Hydrogel reinforced cellulose paper presents enhanced mechanical and conductivity properties that make them suitable as the separator and quasi‐solid electrolyte for paper batteries. The printed zinc batteries (Mn–Zn and Ni–Zn) are flexible, cuttable, and potentially integrable with other paper electronics.
Thermogalvanic cells (TGC) are promising devices for directly converting heat into a stable electric output. The practical applications of TGCs are presently significantly hindered by the low voltage ...(millivolt level) generated from a limited temperature difference. One general strategy for improving the voltage is to alternately connect n-type and p-type redox units in series. However, the number of the possible redox species is limited, hindering the optimization of the series stacking of devices. In this work, we report a novel concept that enables p-n conversion for the iodide/triiodide (I-/I3-) redox couple induced by poly (N-isopropylacrylamide) (PNIPAM) thermo-sensitive nanogels, with the Seebeck coefficient changing from 0.71 mV K−1 to − 1.91 mV K−1. The results prove that the nanogels enable selective capture of I3- at the hot side followed by the release of I3- at the cold side, yielding a concentration gradient of the free I3-, resulting in the p-n inversion. Furthermore, we designed a wearable device consisting of alternating I-/I3- and I-/I3-/nanogels unites in series that generated the open-circuit voltage of approximately 1 V and output power of approximately 9 μW by utilizing body heat. This work developed a new method for inverting the Seebeck effect of redox couples and is highly important for extending the library of possible redox species in TGCs.
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•The p-n conversion for the iodide/triiodide (I-/I3-) redox couple induced by thermo-sensitive nanogels.•The Seebeck coefficient for I-/I3- redox couple was inverted from 0.71 mV K−1 to − 1.91 mV K−1 induced by nanogels.•A wearable device consisting of alternating I-/I3- and I-/I3-/nanogels unites in series can harvest body.
With the proliferation of microelectronic devices, the need for portable power supplies is evidently increasing. Possible candidates for micro energy storage devices are Li-ion batteries and ...supercapacitors. Among them, the flexible solid-state supercapacitors combined with exceptionally long cycle life, high power density, environmental friendliness, safety, flexibility and stability, afford a very promising option for energy storage applications. This paper reviews flexible solid-state electrochemical supercapacitors and the performance metrics. A better practice by calculating released energy to evaluate material and device performance is proposed. In addition, an overview is given of the electrolyte and various electrode materials that are suitable for flexible solid-state supercapacitors. The review summarizes the recent research focusing on novel configurations of flexible solid-state supercapacitors for energy storage and applications, such as freestanding, asymmetric, interdigitated, and fiber-based supercapacitors. Lastly, some discussions on future research are presented.
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•A better practice by calculating released energy to evaluate material and device performance is proposed.•The review discussed electrode materials of solid-state supercapacitors.•The review emphasized novel configurations for high performance flexible solid-state supercapacitors.
Water distillation with solar thermal technology could be one of the most promising way to address the global freshwater scarcity, with its low cost and minimum environmental impacts. However, the ...low liquid water productivity, which is caused by the heat loss and inadequate heat utilization in solar‐thermal conversion process, hinders its practical application. Here, a compact solar‐thermal membrane distillation system with three structure features: highly localized solar‐thermal heating, effective cooling strategy, and recycling the latent heat, is proposed. The steam generation rate is 0.98 kg m−2 h−1 under solar illumination of 1 kW m−2 in the open system, while the liquid water productivity could be 1.02 kg m−2 h−1 with the solar efficiency up to 72% with a two‐level device. The outdoor experiments show a water productivity of 3.67 kg m−2 with salt rejection over 99.75% in one cloudy day. These results demonstrate an easy and high‐efficiency way for water distillation, especially suitable for household solar water purification.
A compact solar thermal membrane distillation system for highly efficient collecting liquid water from saline is presented. The device can achieve liquid water productivity of 1.02 kg m−2 h−1 with the solar efficiency up to 72% under solar illumination of 1 kW m−2.
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