Energy Harvesting Capability Research Articles

Optimization of Structural, Dielectric, and Electrical Properties in Lead-free Ba0.85Ca0.15Zr0.1Ti0.9O3 through site engineering for Biocompatible Energy Harvesting

Piezoelectric energy harvesting has recently gained attention due to its high power density and potential for self-powered sensor networks. This study investigates the effects of dopants on Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) ceramics, examining Strontium (Sr2+), Zinc (Zn2+), and praseodymium (Pr3+/4+) ions at different sites and their impact on structural, dielectric, and electrical properties. X-ray diffraction and Rietveld analysis reveal a coexistence of tetragonal and rhombohedral/orthorhombic phases, with a predominant tetragonal phase, confirmed by Raman analysis. Energy-dispersive X-ray spectroscopy ensures chemical homogeneity. The density measurements indicate a dense microstructure with a relative density of 90-95%. Dielectric analysis shows a relaxor-like behavior in AB-site doped BCZT ceramics, validated by polarization-electric field hysteresis loops. B-site doped BCZT ceramics exhibit ultra-low leakage currents, approximately 103 times lower than undoped BCZT. An optimized biocompatible flexible film-based energy harvester, incorporating A-site doped BCZT ceramic particles, demonstrated impressive energy harvesting capabilities. A simple finger tapping generated ~80.2V and ~18.2nA, with an average peak-to-peak power density of 7.6 µW-cm-3. These results highlight the significant potential of dopant inclusion in BCZT ceramics, marking a major advancement in doping strategies for piezoelectric energy harvesting in miniature electronics.

ZnO with Different Morphologies Sensitized by Metalloporphyrins as Catalysts for H2 Production by Water Splitting Under Sunlight.

In this work, zinc oxide with different morphologies and textural properties were prepared and sensitized with metalloporphyrins (MPs) aiming to improve its solar energy harvesting capability for H2 production by water splitting under sunlight (a 300 W Xe/Hg lamp). An anionic iron(III)porphyrin and a cationic manganese(III)porphyrin were immobilized on different ZnO solids predominantly by electrostatic interactions. In general, the prepared MP-free ZnO solid yielded modest catalytic results which had apparently no direct correlation with their textural properties or morphology. On the other hand, when these ZnO solids had iron or manganese porphyrin sensitizing them, their catalytic performances changed and a superior yield towards H2 production was observed in comparison to the pure ZnO solids, making evident the synergy achieved between these two components (ZnO and metalloporphyrins) for the prepared solids. It was also observed that the metalloporphyrins and the respective free-base ligand suffered redox reactions when used as homogenous catalyst in this reaction, which could influence their performances as catalysts. The same was not observed in the solids containing immobilized MP, suggesting some protective effect of the ZnO solids on the MP complexes upon immobilization probably due to interaction of the complexes with the ZnO matrix.

Boundary Layer Modelling of Flow Acceleration and Energy Transfer Effects in Smart Pavement Design

The integration of remote technology into the construction industry has advanced the emergence of smart, self-learning infrastructure across all levels of land transportation design and development. However, energy harvesting capabilities for smart road ventilation purposes have not yet been fully researched as the world gravitates towards energy sustainability. This study thus presents a mathematical investigation of the self-draining design potentials of road pavements, leveraging on energy absorption and conversion to accelerate conductive and convective ventilation of these pavements during wet conditions, as a means of ensuring the skid resistance and safety of such pavements are not compromised. Applying numerical methods with the aid of commercial software code MATLAB®, the classical physics of fluid-surface interaction was used to model accelerated drainage of microflood off paved surfaces through methodical modification of the thickness of the boundary layer associated with the flow regime over the flat road surface. Results indicate significant influences of energy exchange, thermal, and viscous diffusivity on flow acceleration. Alterations in parameters such as the slip factor, thermally induced Brownian motion or phoretic characteristics of the fluid particles at the boundary induce accelerated flow at the surface of the pavement. The findings contribute to the advancement of smart infrastructure by offering practical insights into the potential benefits of integrating energy-harvesting technologies into road pavement systems. By optimizing flow acceleration mechanisms, smart pavements can play a crucial role in improving road safety and sustainability in urban environments.

Fire safety performance of functional vegetated green building systems: A comprehensive review

The rapid growth of the urban population and the increasing energy consumption of buildings due to global urbanization have led to a significant environmental impact. Therefore, energy conservation, emission reduction, and the adoption of green and low-carbon practices have become the focus of the transformation of construction industry in response to energy shortages and greenhouse gas emissions. This paper focuses on the use of functional green building technologies, specifically the integration of plant microbial fuel cell (PMFC) systems into green building systems, to regulate the indoor and outdoor thermal environment, mitigate the negative effects of urbanization, and enhance building energy efficiency. However, the incorporation of vegetation structures in green building systems significantly increases the risk of fire, necessitating a thorough evaluation of the fire safety system. This paper introduces the working mechanism of functional green building systems with energy harvesting capabilities by PMFC technique, the benefits they bring to the residential environment, and their impact in regulating indoor and outdoor thermal environments while improving building energy performances. Moreover, this paper discusses potential fire hazards caused by vegetation, electrical wire, curtain wall glass, and system layout in PMFC systems. It proposes methods and future research directions to improve safety levels. The paper presents ideas for developing resource-saving and environmentally friendly functional green building systems based on the principles of sustainable development and energy harvesting technology.

Phase transformation enabled textile triboelectric nanogenerators for wearable energy harvesting and personal thermoregulation

The practical applications of environmentally friendly wearable textile triboelectric nanogenerators (t-TENGs) are constrained by inadequate heat dissipation, moisture permeability, and outdoor durability, particularly in humid and high-temperature environments. This study introduces a novel passive cooling strategy by integrating super-hydrophilic titanium dioxide solvent-free TiO2 nanofluids (TiO2 nfs) into cellulose acetate (CA) fibrous membranes (TiO2 nfs@CA) to achieve human comfort and efficient energy harvesting. Interestingly, the phase transformation of TiO2 nfs around boy temperature range (32–38 °C) effectively regulates the surface temperature of TiO2 nfs@CA fibrous membranes. In comparison with pristine CA fabric, TiO2 nfs@CA textile demonstrates exceptional solar reflectance (93.43 %), high infrared emissivity (85 %), excellent water vapor transport rate (12.6 g m−2 h−1), and a significant cooling effect of 4–8 ℃ for both human skin and indoor environments. TiO2 nfs significantly enhances their ultraviolet resistance as well as mechanical properties and dielectric properties while improving triboelectric output performance with output voltage (66 V), current (2.7 μA), and power density (82 mW m−2). And TiO2 nfs@CA t-TENGs exhibit superior multifunctionality in terms of energy harvesting capabilities along with pressure sensing abilities for real-time movement monitoring including foot movements assessment as well as recovery evaluation for human body health maintenance purposes. Overall, TiO2 nfs@CA t-TENGs with the skin-friendly, dyeable, and recyclable properties provides a novel approach towards comfortable self-powered wearable devices that enable practical foot movement prediction alongside health monitoring.

In-situ cured gel polymer/ecoflex hierarchical structure-based stretchable and robust TENG for intelligent touch perception and biometric recognition

Gel-based sensors for next generation touch panels have been acknowledged for their exceptional sensitivity and flexibility. However, these sensors typically depend on a metal grid connection, which is susceptible to structural deformation under heavy stress applications and necessitates external power. Here, we report a novel in-situ cured gel polymer electrode-based triboelectric nanogenerator (GPE-TENG) that is stretchable, semi-transparent, and durable, designed to enable a self-powered touch panel for intelligent touch perception. The in-situ curing of the hierarchical structure of the ionic polymer gel encapsulated within the ecoflex ensures robust adhesion of the ionic conductive polymer gel (PEO/LiTFSI) to the ecoflex layers, addressing the issue of delamination in TENG components under mechanical stress. As a result, the GPE-TENG demonstrates high durability, enduring under stretching of approximately 375 % and sustaining heavy mechanical deformations (under folding, twisting, and rolling) over a long period (approximately 2 months) without loss of functionality. Remarkably, the GPE-TENG exhibits outstanding energy harvesting capabilities with a peak power density of 0.36 W m-2. Notably, the GPE-TENG generates electrical signals through simple device stretching, thus serving as a self-powered wearable sensor for human activity monitoring. Moreover, a 9-digital arrayed (3 × 3) flexible, semi-transparent, and self-powered touch panel based on the GPE-TENG shows multifunctionality, including touch track/pattern recognition (i.e. touch and sliding mode) and a highly accurate (∼98 %) deep learning assisted smart biometric system for user identification.

Topological modes, vibration attenuation, and energy harvesting in electromechanical metastructures

The dynamics of topological boundary modes in both periodic and quasi-periodic electromechanical metastructures is investigated, with a focus on their applications to energy harvesting and vibration reduction. The metastructure analyzed in this study is based on a shunted array of piezoelectric patches, with electrical parameters modulated according to the 1D Aubry–André–Harper model. As a result of this modulation, a fractal spectrum is generated near the central frequency of the resonators, a hallmark of nontrivial topology that enables the emergence of digitally controllable edge states and ensuing localization phenomena at subwavelength frequencies. In this framework, a detailed analysis of the metastructure spectral characteristics is conducted to investigate the influence of the modulation parameters on mode localization, both at the boundaries and within the interior of the beam. Such localization effects are then studied in relation to the energy harvesting, attenuation, and wave transport capabilities of the system. These functionalities point toward the realization of self-powered structures with low frequency and digitally controllable vibration attenuation capabilities, and are considered of significant technological interest in applications involving elastic waves and vibrations, where the ability to precisely control and harness these phenomena could lead to innovative solutions in energy-efficient and adaptive systems.

Dual-Functional Cs3Bi2Br9 for stable all-solid-state photo-rechargeable batteries

In light of the immense potential solid-state photo-rechargeable batteries hold in the efficient utilization of renewable solar energy, there is a rapidly growing demand for materials that possess both energy harvesting and storage capabilities. In this study, a solid-state photo-rechargeable battery has been designed based on the FTO(Fluorine-doped SnO2 transparent conductive glass)/TiO2/Cs3Bi2Br9/Pt/FTO system, which achieves dual functions of photoelectric conversion and energy storage. The inorganic bismuth-based material employed in these batteries exhibits commendable cyclic stability. Under photo-rechargeable conditions, a single cell can maintain an open-circuit voltage as high as 0.45 V in the absence of illumination. By connecting multiple cells in series, we succeed in powering an LED (Light-emitting diode) continuously for 1 min without light exposure. The findings of this research open new avenues for the design and development of novel materials that could enable highly efficient solid-state photo-rechargeable batteries.

Design and experimentation of width tapered meandered array structure for low frequency broadband vibration energy harvesting

A novel 6DoF Tapered beam energy harvester, capable of operating across a broad and low frequency range, is proposed in this work. The hybrid structure incorporates regular beam array and zig-zag sections, enhancing deformation and bending. Width tapering with constant thickness optimizes the structural performance and energy harvesting capabilities of the beam. Tapering ensures even strain distribution, reducing the risk of structural failure. The proposed structure demonstrates wide band characteristics at low frequencies, delivering higher power output compared to an array of cantilevers for a given area. FEM analysis is conducted to optimize proof mass, aiming for closely spaced resonance frequencies and high-power output. Experimental validation on a prototype confirms the accuracy of the frequency response predicted by the models. Under harmonic base excitation of 0.4 g, the harvester yields an average DC power of 2497 μW, accounting for signal conditioning losses, within the frequency range of 9–20 Hz. The suggested structure offers excellent design flexibility, allowing adjustment of resonant frequencies by varying the number of beams, the slope and the proof mass of individual beams. The geometry of the proposed structure provides versatility, mechanical resilience, uniform strain distribution make it suitable for developing MEMS energy harvesters.

Simultaneous low-frequency vibration isolation and energy harvesting via attachable metamaterials

In this study, we achieved energy localization and amplification of flexural vibrations by utilizing the defect mode of plate-attachable locally resonant metamaterials, thereby realizing compact and low-frequency vibration energy suppression and energy harvesting with enhanced output performance. We designed a cantilever-based metamaterial unit cell to induce local resonance inside a periodic supercell structure and form a bandgap within the targeted low-frequency range of 300–450 Hz. Subsequently, a defect area was created by removing some unit cells to break the periodicity inside the metamaterial, which led to the isolation and localization of the vibration energy. This localized vibration energy was simultaneously converted into electrical energy by a piezoelectric energy harvester coupled with a metamaterial inside the defect area. Consequently, a substantially enhanced energy harvesting output power was achieved at 360 Hz, which was 43-times higher than that of a bare plate without metamaterials. The proposed local resonant metamaterial offers a useful and multifunctional platform with the capability of vibration energy isolation and harvesting, while exhibiting easy handling via attachable designs that can be tailored in the low-frequency regime.

Rod-type handheld hybrid nanogenerator for mechanical energy harvesting and self-powered speed sensing applications

Nanogenerators offer a promising solution for converting mechanical movements into electricity with significant implications for portable electronics. Herein, we propose a novel approach using magnesium (Mg)-doped zinc oxide (ZMO) nanoflakes (NFs) embedded in polydimethylsiloxane (PDMS) composite films, which serve as the negative tribo-layer in a triboelectric/piezoelectric hybrid nanogenerator (HNG) operating in contact-separation mode. The ZMO NFs, with an optimized Mg concentration for a high dielectric constant, are mixed into PDMS, and their concentration is further optimized to achieve the highest electrical output from the HNG. The optimized device generates a voltage, current, and power density of approximately 186 V, 5.23 μA, and 1.56 W/m2, respectively while also exhibiting high stability. The electricity generated by this HNG is successfully utilized to power commercial portable electronics. To further enhance its practicality, six similar HNGs were fabricated and integrated into a 3D printed structure, forming a rod-type handheld HNG (RTH-HNG). The energy-harvesting capability of the RTH-HNG is systematically investigated under applied external forces. Additionally, the speed-sensing ability of the RTH-HNG during hand-shaking motions is assessed, with the system demonstrating an accuracy of up to 94 % when compared to a commercially available infrared sensor. Moreover, the real-time vibrational energy harvesting capability of the RTH-HNG was demonstrated by attaching it to a bicycle. Therefore, the proposed RTH-HNG can function not only as a mechanical energy harvester for powering small portable electronics but also as a self-sufficient speed sensor for various real-time applications.

Impact of Ca2+ and Zr4+ substitution on mechanical energy harvesting response of lead-free BaTiO3 piezoceramics with thermally stable storage density and efficiency

The Ba1-xCaxZryTi1-yO3 (BCZT; x = 0.18, y = 0.08; x = 0.15, y = 0.10; x = 0.12, y = 0.12; x = 0.09, y = 0.14; both x and y are in mol. %) piezoceramics were prepared by solid-state reaction method and investigated their energy storage and harvesting responses. The composition x = 0.15, y = 0.10 ( i.e. BCZT-2) reveals the morphotropic phase boundary (MPB) near room temperature with enhanced piezoelectric properties such as piezoelectric charge coefficient (d33) ∼ 380 pC/N, piezoelectric strain coefficient (d33*) ∼ 583.71 pm/V, piezoelectric voltage coefficient (g33) ∼ 14.09 ×10−3Vm/N, figure of merits (d33×g33) ∼ 5.35 ×10−12m2/N and the electromechanical coupling coefficient (kp) ∼ 0.291. The harvested peak-to-peak open circuit AC voltage is 30 V and the calculated current is in the range of 0.02–0.14 mA with varied load resistance and the maximum obtained power density is 13.38 μW/mm3 for BCZT-2 ceramics. The DC output signal of BCZT-2 ceramics successfully lit up the 'FCLNT' panel consisting of 53 red LEDs. At room temperature, BCZT ceramics have a recoverable energy storage density (Wrec) and storage efficiency (η) in the range between 506.46 and 257.49 mJ/cm3 and 50.53 – 64.93 % respectively. The composition x = 0.12, y = 0.12 (i.e. BCZT-3) revealed the highest energy storage efficiency (η) ∼ 64.93 % at room temperature. Nonetheless, the temperature-dependent (till its Curie temperature) maximum obtained Wrec of all BCZT ceramics is found in the range between 238.41 and 446.49 mJ/cm3 with an η of 66.98–79.67 %. Thus, compositionally tuned BCZT ceramics exhibit considerable piezoelectric properties, including energy storage and harvesting capabilities.

First-principles study of optoelectronic and thermoelectric aspects of novel zintl phase SrAg2X2 (X = S, Se, Te) alloys for green energy applications

This work comprehensively investigates the solar energy harvesting and thermoelectric capabilities of innovative Zintl phase SrAg2X2 (X = S, Se, Te) alloys. Herein, the analysis of the structural, optoelectronic, and thermoelectric characteristics of Zintl SrAg2X2 (X = S, Se, Te) compounds has been conducted utilizing the WIEN2k code. The formation energy has been evaluated to elaborate the thermodynamic stability of Zintl compounds. The materials demonstrate characteristics of semiconductors, with anticipated band gap values of 1.78 eV for SrAg2S2, 1.63 eV for SrAg2Se2, and 1.50 eV for SrAg2Te2. The optical characteristics have been examined to assess the potential use of these phases in optoelectronic and photovoltaic systems. The standard Boltzmann transport theory has been used to analyze thermoelectric parameters concerning temperature and chemical potential. Thermoelectric features have also verified the p-type characteristics of these semiconductors. Considerably higher predicted values of the power factor and higher figure of merit demonstrate the capability of thermal energy conversion. Consequently, these outstanding optoelectronic and thermoelectric aspects values indicate that this class of materials may be highly suitable for use in solar and thermoelectric systems.

A Thermosensitive Ionic Hydrogel for Thermotropic Smart Windows With Integrated Thermoelectric Energy Harvesting Capability

AbstractHarvesting low‐grade waste heat into electrical energy is recognized as a promising solution for sustainable energy supply. In parallel, thermotropic smart windows have emerged as an efficient way to reduce building energy consumption. It is posit that thermotropic smart windows with inherent thermoelectric property may offer unique advantages for practical applications. Herein, the preparation and characterization of a series of ionic hydrogels that exhibit temperature‐sensitive phase transition behavior is reported, which are suitable for both thermotropic smart windows and thermoelectric generators. Notably, the lower critical solution temperature (LCST) of this ionic hydrogels can be feasibly modulated, and the thermoteopic phase transition also induces a sharp increase in their Seebeck coefficient, reaching up to 39.03 mV K−1 with a power factor (PFi) value up to 0.838 mW m−1 K−2. A prototype dual functional thermotropic smart window that simultaneously works as an ionic thermoelectric generator is further demonstrated, achieving both efficient phase transition driven by solar heat at ≈26 °C and an energy density up to 250 mJ m−2. This study offers new opportunity for the development of smart materials that can bridge the gap between thermal comfort and energy sustainability for energy harvesting and smart building applicat.

Multifunctional Thermochromic Dye‐Integrated Hybrid Nanogenerators for Mechanical Energy Harvesting and Real‐Time IoT Sensing

AbstractHybrid nanogenerators are advanced mechanical energy harvesters capable of simultaneously scavenging multiple types of energy. Additionally, thermochromic materials provide a practical and visually assessable method for real‐time temperature monitoring. In this report, a novel energy harvester and sensing patch (EHSP) is introduced, that utilizes combined piezoelectric and triboelectric effects to harvest mechanical energy efficiently. To optimize the EHSP, various energy harvester configurations are fabricated and tested, and the dielectric properties of triboelectric films are systematically investigated. These improvements are implemented to augment the overall energy harvesting capability. The thermochromic properties of the EHSP are also explored to enhance both the electrical performance and thermal responsiveness. The EHSP demonstrates the ability to generate maximum voltage and current outputs of 350 V and 20.4 µA, respectively. Moreover, it can detect temperature changes within seconds, making it suitable for both energy harvesting and sensing applications. The EHSP is tested in practical scenarios, proving its efficiency as an energy harvester and sensor for everyday human activities. Furthermore, its integration with multiple hybrid nanogenerators showcases its potential for industrial and wearable sensing applications.

Effect of stability state transition of variable potential well in tri-hybridized energy harvesters

Energy harvesting is a crucial technology for self-powering wireless sensor nodes and mobile terminals. In addressing this, we utilized a variable potential well to create a tri-hybrid energy harvester that integrates piezoelectric effect, electromagnetic induction, and triboelectric effect. The compression and stretching of a compressible magnet-spring oscillator alter the system’s potential well, thereby promoting the operation of the piezoelectric unit (PU), electromagnetic unit (EU), and triboelectric unit (TU). A coupled electromechanical model using Hamilton’s principle was established. By calculating the static potential energy and restoring force, we discussed the stability state transition, revealing that when the magnet distance is less than 38 mm, the system transitions from a mono-stable to a bi-stable state. The experimental study investigated the impact of excitation and structural parameters on voltage and power. A high excitation level enhances all three units. The TU demonstrates excellent electrical performance under high potential energy in the bi-stable state, while the PU performs best in mono- and bi-stable switching structure. The EU shows relatively balanced electrical performance across various conditions. These findings offer new insights into enhancing energy harvesting capabilities for external circuits.

Photo-annealed electrospun TiO2 nanofibers as ion-storage layer for self-rechargeable Zn-based electrochromic energy storage device

Developing a self-rechargeable transparent electrochromic energy storage device (EESD) is highly demanding for advancing electrochromic technology and energy harvesting capabilities. In this study, we introduce a room-temperature photo-annealing method to fabricate electrospun titanium oxide (TiO2) nanofibers, serving as an ion-storage layer (ISL) on the counter electrode. By monitoring the composition and morphology of the precursor before and after ultraviolet/ozone irradiation, we confirm the formation of oxide nanostructures in electrospun TiO2 nanofibers, which enhances ion transport in the fabricated EESDs. The structural and surface properties of the photo-annealed ISL are comprehensively analyzed using various characterization techniques. Enhanced electrochromic performances are evidenced through cyclic voltammetry, spectroelectrochemical measurements, and charge storage assessments. The Zn-based EESDs with ISL (ISL Zn-EESDs) display rapid electrochemical kinetics, high charge-storing capacities, and long lifespans, with open-circuit potential of 1.2 V, optical contrast of 77 %, discharge capacity of 92 mA h/g, coloration efficiency of 58.63 cm2/C, and 99.9 % efficiency retention up to 250 cycles in both flat and bent states. Furthermore, the practical viability of the ISL Zn-EESDs is demonstrated by powering an LED lamp for several minutes. This approach highlights the potential of ISL Zn-EESDs for developing flexible smart windows, opening up a range of promising applications.

Flexible ZIF-67@PVDF tree-like nanofiber membrane with high piezoelectric output for energy harvesting

Modern demands for efficient, environmentally friendly, and self-powered devices have led to growing interest in piezoelectric polymers in the scientific community. In this paper, a ZIF-67 functionalized polyvinylidene fluoride/ tetrabutylammonium hexafluorophosphate tree-like nanofiber membrane (ZIF-67@PVDF/TBAHP-TLNMs) was developed as piezoelectric nanogenerator for energy harvesting. The ZIF-67@PVDF/TBAHP-TLNMs was prepared by in-situ growth of ZIF-67 on the surface of PVDF TLNMs, which demonstrated remarkable energy harvesting capabilities. The results indicated that the β-phase content of the in-situ growth of ZIF-67 reached 86.94 %, augmented the fiber's rotation radius, and elevated the electromechanical conversion efficiency. Notably, the short circuit current reached 3.87 μA and the output voltage exceeded 9.78 V, which was 10.7 times and 5.9 times higher than the electrical signal output of pure PVDF nanofiber membrane, respectively. Furthermore, the ZIF-67@PVDF/TBAHP-TLNMs exhibited exceptional mechanical properties, with an elastic modulus as high as 1.13 GPa, outperforming other nanofiber membranes and catering to the diverse requirements of wearable devices. During a 500 s test cycle, its layered structure remained intact, without any discernible damage or interlayer separation of the nanofibers. At the same time, the device exhibited high electromechanical conversion efficiency and a sensitive sensing function, which made it have broad application prospects in human motion monitoring and intelligent wearable devices.

Hydrovoltaic Effects from Mechanical-Electric Coupling at the Water-Solid Interface.

The natural water cycle on the Earth carries an enormous amount of energy as thirty-five percent of solar energy reaching the Earth's surface goes into water. However, only a very marginal part of the contained energy, mostly kinetic energy of large volume bulk water, is harvested by hydroelectric power plants. Natural processes in the water cycle, such as rainfall, water evaporation, and moisture adsorption, are widespread but have remained underexploited in the past due to the lack of appropriate technologies. In the past decade, the emergence of hydrovoltaic technology has provided ever-increasing opportunities to extend the technical capability for energy harvesting from the water cycle. Featuring electricity generation from mechanical-electric coupling at the water-solid interface, hydrovoltaic technology embraces almost all dynamic processes associated with water, including raining, waving, flowing, evaporating, and moisture adsorbing. This versatility in dealing with various forms of water and associated energy renders hydrovoltaic technology a solution for fossil fuel-caused environmental problems. Here, we review the current progress of hydrovoltaic energy harvesting from water motion, evaporation, and ambient moisture. Device configuration, energy conversion mechanism mediated by mechanical-electric coupling at various water-solid interfaces, as well as materials selection and functionalization are discussed. Useful strategies guided by established mechanisms for device optimization are then covered. Finally, we provide an outlook on this emerging field and outline the challenges of improving output performance toward potential practical applications.

Phase evolution and piezoelectric properties of SnO2 doped KNN based piezoceramics

The present research focuses on the electrical properties of lead-free piezoceramics (0.985-x)(K0.485Na0.485Li0.03)(Nb0.96Sb0.04)O3-0.015(Bi0.5Na0.5)ZrO3-xSnO2 (KNNLS-BNZ-xSnO2, x = 0.003, 0.006, 0.009, 0.012, and 0.015). This study examines the influence of varying SnO2 doping levels on the microstructure and piezoelectric properties of the ceramics. All the ceramics prepared demonstrate pure perovskite structure without any secondary phases. The Rietveld refinement analysis of XRD data reveals the existence of multiphase evolution around room temperature. The tetragonality (c/a) and cell volume of the ceramics tend to rise with an increase in Sn4+ content, potentially leading to improved ferroelectric characteristics. The optimum values obtained were Curie temperature (Tc) = 395 oC, remnant polarization (Pr) = 21.07 μC/cm2, piezoelectric coefficient (d33)=357 pC/N, piezoelectric voltage constant (g33) = 24 × 10−3 Vm/N, and figure of merit (FOMoff) = 10.34 pm2/N, corresponding to the ceramic doped with x = 0.012 SnO2. The findings indicate that an optimal amount of Sn4+ in the host composition KNNLS-BNZ improves piezoelectric properties by constructing an R-O-T phase boundary near room temperature. This study suggests that the ceramic with x = 0.012 SnO2 exhibits a favorably high Tc coupled with an exceptional energy harvesting capability, making it a suitable candidate for energy harvesting applications.