Energy Harvesting Materials Research Articles

Materials for energy harvesting, conversion, storage, environmental engineering and sustainability

Materials for energy harvesting, conversion, storage, environmental engineering and sustainability

Self-healed inorganic phase change materials for thermal energy harvesting and management

• First report on giving self-healing property to inorganic phase change materials; • Phase segregation and supercooling were inhibited by hydrogel and graphite; • Low-grade thermal energy harvesting and management were achieved. Inorganic phase change materials, especially for salt hydrate, possess superior energy storage density and thermal conductivity compared with organic phase change materials in low-grade thermal energy harvesting and management fields. More importantly, inorganic phase change materials are safer than that of organic phase change materials in terms of flammability and toxicity. While, supercooling associated with phase segregation and stability of inorganic phase change materials have heavily hindered them from wide practical application. On the other hand, relatively poor shape flexibility is another key drawback that will limit the application scope of inorganic phase change materials. With the aim at making the use of advantages of inorganic phase change materials and avoiding the above-mentioned drawbacks, firstly, sodium acetate trihydrate was used as a thermal energy storage medium, acrylamide and aqueous starch worked corporately, for the first time, to render self-healing (efficiency reach to 75%) and flexible property to the phase change materials composite, and the latent heat of the composite could reach to 134 J/g. In addition, interestingly, we found the addition of carbon material, graphite, could not only efficiently solve the supercooling, but also enhance cyclability of the composite phase change materials. Thanks to the self-healing and flexibility, the as-prepared materials could be used uneventfully in low-grade thermal energy harvesting and management of electronic and wearable device.

Characterizing graphite-based pencil material for mechanical energy harvesting and sensing application

Characterizing graphite-based pencil material for mechanical energy harvesting and sensing application

Intelligent Control of SMART Materials for Energy Harvesting and Storage Devices

The investigation of innovative materials and intelligent control systems has been motivated by the desire to provide sustainable energy solutions, with the aim of improving the efficiency and adaptability of energy harvesting and storage devices. This study introduces an innovative methodology to tackle this issue by combining SMART (Self-Monitoring, Analysing, and Reporting Technology) materials with sophisticated intelligent control approaches. The system under consideration utilises the intrinsic material characteristics of SMART materials, including piezoelectric, thermoelectric, and shape memory alloys, with the objective of capturing and transforming ambient energy into electrical power that can be effectively utilised. In order to fully harness the capabilities of SMART materials, a novel control framework is proposed that integrates machine learning algorithms, real-time sensor data, and adaptive control procedures. The intelligent control system enhances the effectiveness and durability of energy harvesting and storage devices by effectively adjusting to different operational situations and optimising energy conversion and storage processes. The findings demonstrate significant enhancements in energy conversion efficiency as well as notable advancements in the longevity and dependability of energy systems utilising SMART materials. Furthermore, the capacity of the control system to adjust to various environmental circumstances and energy sources situates this research at the forefront of cutting-edge energy technology.

Perspectives on recent advancements in energy harvesting, sensing and bio-medical applications of piezoelectric gels.

The development of next-generation bioelectronics, as well as the powering of consumer and medical devices, require power sources that are soft, flexible, extensible, and even biocompatible. Traditional energy storage devices (typically, batteries and supercapacitors) are rigid, unrecyclable, offer short-lifetime, contain hazardous chemicals and possess poor biocompatibility, hindering their utilization in wearable electronics. Therefore, there is a genuine unmet need for a new generation of innovative energy-harvesting materials that are soft, flexible, bio-compatible, and bio-degradable. Piezoelectric gels or PiezoGels are a smart crystalline form of gels with polar ordered structures that belongs to the broader family of piezoelectric material, which generate electricity in response to mechanical stress or deformation. Given that PiezoGels are structurally similar to hydrogels, they offer several advantages including intrinsic chirality, crystallinity, degree of ordered structures, mechanical flexibility, biocompatibility, and biodegradability, emphasizing their potential applications ranging from power generation to bio-medical applications. Herein, we describe recent examples of new functional PiezoGel materials employed for energy harvesting, sensing, and wound dressing applications. First, this review focuses on the principles of piezoelectric generators (PEGs) and the advantages of using hydrogels as PiezoGels in energy and biomedical applications. Next, we provide a detailed discussion on the preparation, functionalization, and fabrication of PiezoGel-PEGs (P-PEGs) for the applications of energy harvesting, sensing and wound healing/dressing. Finally, this review concludes with a discussion of the current challenges and future directions of P-PEGs.

Light harvesting hexamolybdenum cluster integrated with the 3D ordered semiconductor inverse opals for optoelectronic property

Solar energy-harvesting materials have significantly contributed to the development of energy-saving applications for several decades. We have mainly used a new concept composed of the electrophoretic deposition technique and photonic crystal structural engineering to understand the tunable light-absorption and electronic conduction properties. A hexamolybdenum cluster compound (denoted as the Mo6 cluster) was successfully functionalized on a tin pyrophosphate semiconductor integrated within an inverse opal photonic crystal. The size of the periodical pores, surface modification, and chemical composition of the infiltration material of the inverse opal film have been investigated to control the photonic bandgap in the visible range and the efficiency of the deposited Mo6 cluster. The photoactive Mo6 clusters act as a visible light harvester and generate an efficient photo-induced current upon light absorption that is enhanced by a slow photon effect occurring at the photonic stopband edges. The electron and proton are transferred in the inorganic-organic network via hydrogen bonds by a hopping mechanism to generate a rapid photoconductivity response during light irradiation. Specific attention focused on the role of humidity and temperature regarding the reproducibility of the experiments and the photosensitivity of the nanocomposite. The suitable tunable photo-induced conduction property in organic-inorganic materials opens a new opportunity for the applicability of cluster-based compounds in visible optoelectronic devices.

Halide double perovskite-based efficient mechanical energy harvester and storage devices for self-charging power unit

With the rapid development of portable/wearable electronic devices, the demand for highly efficient and sustainable self-powered systems to support their off-grid operation has risen considerably. Recently, metal halide perovskites (MHPs) have been suggested as promising materials for energy harvesting and storage devices because of their excellent optoelectronic, ferro/piezoelectric, and ion migration properties. However, the high toxicity and poor physicochemical stability of MHPs hamper their practical application. Herein, for the first time, the potential of methylammonium tin halide (MA2SnX6; X = Cl, Br, and I) double perovskite thin films for high-efficiency self-charging power units (SPUs) is elucidated by virtue of their high stability in air. To this end, the integration of an MA2SnCl6-based piezoelectric nanogenerator (PENG) with a lithium metal battery (LMB), which also uses an MA2SnCl6-based thin film as the cathode, is demonstrated. The MA2SnCl6-based PENG exhibited a high output power density of 7.33 μW cm−2 and an excellent mechanical durability. Furthermore, MA2SnCl6 as a cathode in LMB recorded the highest specific capacity of 589.98 mAh g−1. A 1 nm-thick Al2O3 coating on the MA2SnCl6 surface improved the capacity retention from 16.9 % to 75.1 % for 100 cycles, indicating its stable performance. The MA2SnCl6-based LMB is charged by the MA2SnCl6-based PENG and utilized as an SPU for operating various small-scale electronics (humidity meter, calculator, and LED). This work not only demonstrates the feasibility of MHPs toward high-capacity batteries and energy harvesters but also provides insights into the general design principles of MHP-based devices.

Rational Design of Advanced Triboelectric Materials for Energy Harvesting and Emerging Applications

The properties of materials play a significant role in triboelectric nanogenerators (TENGs). Advanced triboelectric materials for TENGs have attracted tremendous attention because of their superior advantages (e.g., high specific surface area, high porosity, and customizable macrostructure). These advanced materials can be extensively applied in numerous fields, including energy harvester, wearable electronics, filtration, and self-powered sensors. Hence, designing triboelectric materials as advanced functional materials is important for the development of TENGs. Herein, the structural modification methods based on electrospinning to improve the triboelectric properties and the latest research progress in this kind of TENGs are systematically summarized. Preparation methods and design trends of nanofibers, microspheres, hierarchical structures, and doping nanomaterials are highlighted. The factors influencing the formation and properties of triboelectric materials are considered. Furthermore, the latest progress on the applications of TENGs is systematically elaborated. Finally, the challenges in the development of triboelectric materials are discussed, thereby guiding researchers in the large-scale application of TENGs.

Piezoelectric ceramic materials on transducer technology for energy harvesting: A review

Recently, energy harvesting through the means of piezoelectric transducer technology has increasingly attracted the attention of engineers and scientists in producing/generating electricity for human consumption. However, understanding of piezoelectric materials for application in piezoelectric transducer devices in energy harvesting remains important in today’s energy systems engineering. Thus, the present review study is centered on piezoelectric materials for a better understanding of the properties of different piezoelectric materials (ceramic) when placed under mechanical stress or vibration and electrical field during energy harvesting using transducer devices. With the available literature, lead zirconate titanate materials showed to be the most common piezoelectric material with a high energy-generating performance but possessed more mechanical failure and also compromised in a harsh environment compared to lead-free piezoelectric materials. As such, the authors conclude that lead-free piezoelectric materials, such as zinc oxide and barium titanate, remain the best conducive piezoelectric material over lead zirconate titanate, which basically affects the human environment due to its toxicity. Thus, to widen the use of lead-free piezoelectric materials in energy harvesting, owing to their improved properties and environment-friendly nature, the authors recommend further enhancement of the lead-free piezoelectric material properties via nanodielectric filler incorporations using the spark plasma sintering technique.

The Effect of Electrospinning Parameters on Piezoelectric PVDF-TrFE Nanofibers: Experimental and Simulation Study

Polyvinylidene fluoride and its copolymers can be used as active materials for energy harvesting and environmental sensing. Energy harvesting is one of the most recent research techniques for producing stable electrical energy from mechanical sources. Polyvinylidene fluoride–trifluoroethylene (PVDF-TrFE) is applicable for sensors and self-powered devices such as medical implants and wearable electronic devices. The preparation of electrospun P(VDF-TrFE) nanofibers is of great interest for the fabrication of sensors and self-powered devices, nanogenerators, and sensors. In this regard, it is necessary to investigate the effects of various parameters on the morphology and piezoelectric output voltage of such nanofibers. In this study, we have examined the effect of concentration and feed rate on the nanofiber diameter. It has been found that by increasing the concentration and feed rate of the polymer solution, the diameter of the nanofibers increases. The experimental results and the finite element method (FEM) simulation have also shown consistency; when the nanofiber diameter increases, the output voltage of the nanofibers decreases. This behavior can be related to the strain reduction in the deformed nanofibers.

Using Photonic Glasses as Colored Covers for Solar Energy Harvesting

AbstractThe increasing demand for renewable energy is promoting technologies that integrate solar energy harvesting materials with the human living environment, such as building‐integrated photovoltaics. This places requirements on developing colored covers with a trade‐off between efficiency and aesthetics, providing a new stage for the large‐scale application of structural color technologies. This study investigates the theoretic feasibility of employing the photonic glass, a random packing of monodisperse dielectric microspheres, as the colored cover for solar energy harvesting. Based on numerous optical simulations, the color and average solar transmissivity of the photonic glasses with varying parameters are evaluated. Results show that using non‐absorbing microspheres with relatively high refractive index, about 3 µm thick photonic glasses can enable colors with lightness over 50 while keeping average solar transmissivity over 80%. Due to the short‐range structural correlation, it is demonstrated that photonic glasses can generate purple, blue, cyan, light green, and gray colors, but cannot help with yellow and red hues. Finally, the effects of several enhancement methods are clarified, and possible ways for expanding the color range are demonstrated. These results provide a comprehensive guide to the practical implementations of structural color using photonic glasses, particularly in the colorization of solar energy materials.

Piezoelectric energy harvesters: A critical assessment and a standardized reporting of power-producing vibrational harvesters

Energy harvesting devices have emerged as an auspicious sustainable energy source for low-power electronics, where delivering electricity using conventional means is not feasible nor desirable. This clear technological impact has drawn huge attention and driven research into energy harvesting materials and devices. Reports are often published, even in high-caliber journals claiming high-efficiency devices. However, these are typically based on poorly defined or even undefined metrics and lack the details needed for re-evaluation and comparing different devices for peer assessment. The enthusiasm to publish is pushing the field towards qualitative rather than quantitative research. Here, after introducing the basic concepts of energy harvesting, randomly selected research papers on piezoelectric energy harvesting devices published over the last two decades, have been assessed. It is shown that essential parameters which are needed for a quantitative evaluation of materials and devices are missing from nearly 90% of the reviewed papers, thus rendering them less reproducible (or even irreproducible) for peer assessment. Such a frequent occurrence of improper data reporting damages the credibility and reliability of the energy harvesting field. To enhance reproducibility and facilitate progress, we herein suggest a measurement and data reporting protocol that should be followed when reporting energy harvesting devices and concomitant performances. The standardized protocol can be further adapted for other vibrational harvesters based on other mechanisms such as triboelectricity.

Optical Properties of Novel Materials for Optoelectronic Applications

Abstract:Energy generation and utilization have always been a prerequisite for human society, however, in the 21st century and after the pandemic of COVID-19 situations, the importance and demand for energy storage devices have been stretched to the next level. Smart energy storage devices are required to cover this indispensable demand so that the desired energy can judiciously be delivered whenever required. For this immense effort, a variety of materials, viz. carbonaceous materials, transition metal composites, conducting polymers, etc., are being employed by the scientific community, which are equipped with advanced performance, flexibility, tunability, portability, and cost-effectiveness. Apart from these specific features, these energy harvesting materials are associated with inherent properties such as high electrical and optical conductivity, which place them as a potential contender to be used in energy harvest and storage devices. These energy storage devices can be based on the electrochemical, electrical, and optical properties of these conductive materials. To be particular, in this review, the study is targeted at optically conductive materials. The optical conductivity of a material depends upon the band gap present in the conductive material under investigation, the lower the band gap, the higher the chance of optical conductivity. This band gap of the material depends upon factors such as the material used, dopant, solvent applied, etc. This review brings the detail of optically conductive materials, understanding the factors affecting the optical conductivity and the methods to enhancing it so that the variety of applications such as solar cells, optoelectronics, photoelectronic, etc., can be improved.

A Critical Review on the Progress of Kesterite Solar Cells: Current Strategies and Insights

AbstractKesterite Cu2ZnSn(S,Se)4 (CZTSSe) with earth‐abundant and environmental‐benign constituents has been regarded as a promising solar energy harvesting material for green and cost‐effective photovoltaic applications. The record efficiency of CZTSSe solar cells has recently been refreshed twice after years‐long stagnation, keeping it in the spotlight. Nevertheless, the champion efficiency of 13.6% is still far behind its counterpart Cu(In,Ga)Se2 (CIGS) (23.35%) despite being endowed with a similar electronic structure and nearly‐identical device architecture. In fact, CZTSSe solar cells are more susceptible to non‐radiative recombination at bulk and interfaces, which must be improved for further efficiency advancement. In this review, the state‐of‐art strategies to enhance the power conversion efficiency of CZTSSe solar cells are summarized and discussed, with focus given to three critical device regions i) kesterite absorber, ii) buffer/kesterite interface, and iii) kesterite/back contact interface. With the further elucidation of the latest progress and disclosure of fundamental mechanisms, novel insights toward high‐efficiency kesterite solar cells are proposed.

Bioinspired ultra-stretchable dual-carbon conductive functional polymer fiber materials for health monitoring, energy harvesting and self-powered sensing

Highly stretchable and multifunctional wearable electronics have shown a desirable attraction recently. However, most fiber-based devices are hindered by the dilemma of stretchability and sensitivity, as well as the decline of performance due to delamination. Herein, a bis-condensed inspired ultra-stretchable dual-carbon fiber (MSSS fiber) is proposed based on the synergistic interaction and tunneling effect of multi-walled carbon nanotube (MWCNTs)-superconductive carbon black (SCCB)-poly[styrene-b-isoprene-b-styrene] (SIS) conductive polymer composite (CPC) and a strong interlocked layer-by-layer structure. The MSSS fiber is developed as a strain sensor with good electric conductivity and stability, ultra-stretchability, high sensitivity (GF = 1,096 at 1,100 %), and good durability (10,000 at 1,000 %) which shows excellent sensing for various motion applications. Simultaneously, the MSSS fiber is also exploited as a single-electrode fiber-based triboelectric nanogenerator (F-TENG) by triboelectric material coating. It demonstrates a significant output power, good durability over 25,000 cycles and stable electric output performance under high-level deformation (600 %), endowing its reliability as a power source supply and self-powered sensing device. This ultra-stretchable conductive fiber further explores the development of multifunctional subtle wearable electronics. The applications of healthcare sensing and energy harvesting also give promising potential in the field of smart wearable electronics, human–computer interaction, and artificial intelligence.

Encapsulation of Nanoparticles into Preformed Block Copolymer Micelles Driven by Competitive Solvation: Experimental Studies and Molecular Dynamic Simulations

We investigate the encapsulation of polymer-tethered nanoparticles (NPs) inside block copolymer (BCP) micelles, which turns to the mutual stabilization of BCP micelles and NPs by each other. It has been demonstrated, for the first time, that in the presence of cosolvent, which is selective for the core-forming block, the encapsulation of polymer-tethered NPs into the core of preformed BCP micelles is feasible. Furthermore, interestingly, in a certain range of cosolvent volume fraction, NP/BCP hybrid micelles comprising a single NP in the micelle core could be obtained. Significantly, in the presence of cosolvent the NP-loaded hybrid micelles remain intact, whereas the NP-free (empty) micelles undergo further transformations. The experimental observations are additionally supported by the results obtained from the molecular dynamic simulation. In particular, our modeling recognizes mechanisms for the formation of NP/BCP hybrids, which include a one-by-one adsorption of individual BCP chains onto the NP surface, fusion of NP with the preformed BCP micelles, or a combination of both mechanisms. The present work provides new opportunities for the fabrication of BCP-based hybrid nanomaterials having potential applications in drug delivery, diagnostics, catalysis, energy harvesting materials, optical devices, etc.

Core‐Shell ZnO@Microporous Organic Polymer Nanospheres as Enhanced Piezo‐Triboelectric Energy Harvesting Materials

AbstractCore‐shell nanospheres were prepared by the homogeneous coating of piezoelectric ZnO nanorod aggregates with triboelectric microporous organic polymer (MOP). The small energy harvesting performance of ZnO@MOP was significantly enhanced, compared with those of ZnO and MOP, due to the piezoelectrification‐induced polarization of inner ZnO and the enhanced generation of tribopositive charges of MOP. Piezo‐triboelectric nanogenerators (PTENGs) fabricated with ZnO@MOP showed peak‐to‐peak voltages of up to 534 V and a maximum power density of 1.19 mW cm−2. In addition, the PTENGs showed excellent durability for 30 000 cycles, demonstrating as efficient power sources for charging electrolytic capacitors and for operating 200 green light emitting diode bulbs.

Core-Shell ZnO@Microporous Organic Polymer Nanospheres as Enhanced Piezo-Triboelectric Energy Harvesting Materials.

Core-shell nanospheres were prepared by the homogeneous coating of piezoelectric ZnO nanorod aggregates with triboelectric microporous organic polymer (MOP). The small energy harvesting performance of ZnO@MOP was significantly enhanced, compared with those of ZnO and MOP, due to the piezoelectrification-induced polarization of inner ZnO and the enhanced generation of tribopositive charges of MOP. Piezo-triboelectric nanogenerators (PTENGs) fabricated with ZnO@MOP showed peak-to-peak voltages of up to 534 V and a maximum power density of 1.19 mW cm-2 . In addition, the PTENGs showed excellent durability for 30 000 cycles, demonstrating as efficient power sources for charging electrolytic capacitors and for operating 200 green light emitting diode bulbs.

Advanced Bacterial Cellulose Ionic Conductors with Gigantic Thermopower for Low-Grade Heat Harvesting.

Ionic conductors such as polymer electrolytes and ionic liquids have high thermoelectric voltages several orders of magnitude higher than electronic thermoelectric materials, while their conductivity is much lower than the latter. This work reports a novel approach to achieve high-performance ionic conductors using calcium ion (Ca2+) coordinated bacterial cellulose (CaBC) through molecular channel engineering. Through the coordination of Ca2+ with cellulose molecular chain, the distance between the cellulose molecular chains is widened, so that ions can transport along the cellulose molecular chain. Therefore, we reported ionic thermoelectric (i-TE) material based on CaBC/NaCl with a relatively high ionic Seebeck coefficient of -27.2 mV K-1 and high ionic conductivity of 204.2 mS cm-1. This ionic hydrogel is promising in the design of high-thermopower i-TE materials for low-grade heat energy harvesting.

(Keynote, Digital Presentation) Prussian Blue Analogues as Electrode Material of Batteries

Prussian blue analogues (PBA), which composed of cyano-bridged jungle-gym type framework and alkali metal ions, are promising material for electrode of batteries, because its framework is robust against electrochemical intercalation/deintercalation of alkali metal ions. In addition, the material consists of ubiquitous elements and is easily synthesized from aqueous solution. Thus, PBAs are promising electrode material for sodium ion secondary battery (SIB). We will introduce the overall features of PBAs as SIB electrode. Furthermore, PBAs are promising material for energy harvesting. We proposed a new type of battery (tertiary battery) that can be charged by the environmental heat using the difference in the thermal coefficient (α= dV/dT) of the redox potential (V) between the anode (αanode) and cathode (αcathode) materials. The tertiary battery can convert the environmental heat energy into electric energy during the thermal cycle, i.e., (i) heating to TH, (ii) discharge at TH, (iii) cooling to TL, and (iv) discharge at TL. In the (i) heating process, the V values of the anode and cathode change by αanodeΔTand αcathodeΔT, respectively. We expect a thermally induced change in the cell voltage (V cell) as large as (αcathode - αanode)ΔT. The stored electric energy can be extracted by the (ii) discharge process at TH. We fabricated several tertiary batteries made of PBA electrodes with different a and evaluated the thermal voltage (Vcell) and discharge capacity (Qcell). For example, NaxCo[Fe(CN)6]0.87/NaxNi[Fe(CN)6]0.94 tertiary battery exhibits Vcell = 24 mV and Qcell = 2.4 mAh/g per unit weight of total active material contains in the cathode and anode. We will correlate the observed Qcell values with the electrode parameters of the tertiary batteries. Y. Shimaura, T. Shibata, and Y. Moritomo, "Interrelation between discharge capacity and charge coefficient of redox potential in tertiary batteries made of transition metal hexacyanoferrate", Jpn. J. Appl. Phys. 61, 044004 (2022)I. Nagai, Y. Shimaura, T. Shibata, and Y. Moritomo, "Performance of tertiary battery made of Prussian blue analogues", Appl, Phys. Express. 14, 094004 (2021).Y. Moritomo, Y. Yoshida, D. Inoue, H. Iwaizumi, S. Kobayashi, S. Kawaguchi, and T. Shibata "Origin of the material dependence of the temperature coefficient of the redox potential in coordination polymers", J. Phys. Soc. Jpn. 90, 063801 (2021).T. Shibata, H. Iwaizumi, Y. Fukuzumi, and Y. Moritomo, "Energy harvesting thermocell with use of phase transition” Sci. Res., 10 1813 (2020)I. Takahara, T. Shibata, Y. Fukuzumi, and Y. Moritomo, " Improved thermal cyclability of tertiary battery made of Prussian blue analogues ", Chem. Select 4, 8558-8563 (2019)Y. Fukuzumi, K. Amaha, W. Kobayashi, H. Niwa, and Y. Moritomo, “Prussian blue analogues as promising thermal power generation materials”, Energy Technology, 6 (2018) 1 – 7.T. Shibata, Y. Fukuzumi, W. Kobayashi, and Y. Moritomo, “Thermal efficiency of a thermocell made of Prussian blue analogues”, Sci. Reps. Appl. Phys. Express. 8 (2018) 14784.T. Shibata, Y. Fukuzumi, W. Kobayashi, and Y. Moritomo, Thermal power generation during heat cycle near room temperature, Appl. Phys. Express. 11, 018101 (2018).M. Takachi, T. Matsuda, and Y. Moritomo, “Cobalt hexacyanoferrate as cathode material of Na+ secondary battery”, Appl. Phys. Express 6, 025802 (2013).M. Takachi, T. Matsuda, and Y. Moritomo, “Redox reaction in Prussian blue analogues with fast Na+ intercalation”, Jpn. J. Appl. Phys. 52, 092202 (2013).