Advances in Triboelectric Nanogenerators for Blue Energy Harvesting and Marine Environmental Monitoring

Blue energy,which includes rainfall,tidal current,wave,and water-flow energy,is a promising renewable resource,although its exploitation is limited by current technologies and thus remains low.This form of energy is mainly harvested by electromagnetic generators(EMGs),which generate electricity via Lorenz force-driven electron flows.Triboelectric nano genera tors(TENGs)and TENG networks exhibit superiority over EMGs in low-frequency and high-entropy energy harvesting as a new approach for blue energy harvesting.A TENG produces electrical outputs by adopting the mechanism of Maxwell’s displacement current.To date,a series of research efforts have been made to optimize the structure and performance of TENGs for effective blue energy harvesting and marine environmental applications.Despite the great progress that has been achieved in the use of TENGs in this context so far,continuous exploration is required in energy conversion,device durability,power management,and environmental applications.This review reports on advances in TENGs for blue energy harvesting and marine environmental monitoring.It introduces the theoretical foundations of TENGs and discusses advanced TENG prototypes for blue energy harvesting,including TENG structures that function in freestanding and contact-separation modes.Performance enhancement strategies for TENGs intended for blue energy harvesting are also summarized.Finally,marine environmental applications of TENGs based on blue energy harvesting are discussed.

Low-frequency blue energy harvesting for sustainable and active anticorrosion

Engineering materials serving in marine surroundings are inevitably corroded.The corrosive marine conditions can also be utilized to harvest kinetic ocean wave energy to solve this problem.Leveraging water–solid triboelectrification to harvest lowfrequency wave energy for active anticorrosion is promising.Existing techniques are efficient in harnessing environmental energy with frequencies higher than 3 Hz,whereas the dominated ocean waves with optimal wave spectral density fluctuate from 0.45 to 1.5 Hz.Herein,we proposed a highly efficient and sustainable blue energy-powered cathodic protection(BECP)strategy by fusing water–solid triboelectric nanogenerators and cathodic protection technology.Leveraging the highly efficient triboelectrification between the moving water and hydrophobic fluorinated ethylene propylene tube,we developed the built-in power module,enabling the harvest of ocean wave energy lower than 1.5 Hz.The generated volumetric current density is 28.9 mA·m^(-3),5–20 times higher than the values of the reported devices.Moreover,the proposed BECP performs comparably to conventional cathodic protection in corrosion inhibition.Significantly,the proposed approach can be easily applied to ships,buoys,and other offshore platforms to simultaneously realize blue energy harvesting and engineering material protection,providing an alternative to traditional active protection technology.

Viability of Harvesting Salinity Gradient (Blue) Energy by Nanopore-Based Osmotic Power Generation

The development of novel materials with ion-selective nanochannels has introduced a new technology for harvesting salinity gradient(blue)energy,namely nanopore power generators(NPGs).In this study,we perform a comprehensive analysis of the practical performance of NPG in both coupon-size and module-scale operations.We show that although NPG membrane coupons can theoretically generate ultrahigh power density under ideal conditions,the resulting power density in practical operations at a coupon scale can hardly reach 10 W·m^(-2) due to concentration polarization effects.For module-scale NPG operation,we estimate both the power density and specific extractable energy(i.e.,extractable energy normalized by the total volume of the working solutions),and elucidate the impact of operating conditions on these two metrics based on the interplay between concentration polarization and extent of mixing of the high-and low-concentration solutions.Further,we develop a modeling framework to assess the viability of an NPG system.Our results demonstrate that,for NPG systems working with seawater and river water,the gross specific extractable energy by the NPG system is very low(~0.1 kW?h?m?3)and is further compromised by the parasitic energy consumptions in the system(notably,pumping of the seawater and river water solutions and their pretreatment).Overall,NPG systems produce very low net specific extractable energy(<0.025 kW?h?m?3)and net power density(<0.1 W?m?2).Our study highlights the significant practical limitations in NPG operations,casting doubt on the viability of NPG as a technology for blue energy harvesting.

The Blue Stragglers and the Integrated Spectral Energy Distribution of Single Stellar Populations

Blue stragglers are a common observational fact for the Galactic clusters. Single Stellar Populations (SSPs) are basic to the studies of galaxy structre and evolution. SSPs are mainly based either on the observation of the integrated properties of star clusters, or on the theoretical understandings of single star evolution. Both of the two ways of making SSPs suffer from either observational uncertainties concerning field contaminations or lack of good models for close binary systems. Based on the photometry of the classical open cluster M67 and the thorough membership survey, we made a color-magnitude diagram (CMD) of high membership stars for the cluster. We will show that by including the contributions of the bright blue stragglers that is common to open clusters, the integrated properties of the clusters are quite different from tranditional SSP models. We further conclude that these blue light contributors are very important to SSP models, and may cast new lights on its applications in the studies of galaxies.

Triboelectric nanogenerators:the beginning of blue dream

Wave energy is inexhaustible renewable energy.Making full use of the huge ocean wave energy resources is the dream of mankind for hundreds of years.Nowadays,the utilization of water wave energy is mainly absorbed and transformed by electromagnetic generators(EMGs)in the form of mechanical energy.However,waves usually have low frequency and uncertainty,which means low power generation efficiency for EMGs.Fortunately,in this slow current and random direction wave case,the triboelectric nanogenerator(TENG)has a relatively stable output power,which is suitable for collecting blue energy.This article summarizes the main research results of TENG in harvesting blue energy.Firstly,based on Maxwell’s displacement current,the basic principle of the nanogenerator is expounded.Then,four working modes and three applications of TENG are introduced,especially the application of TENG in blue energy.TENG currently used in blue energy harvesting is divided into four categories and discussed in detail.After TENG harvests water wave energy,it is meaningless if it cannot be used.Therefore,the modular storage of TENG energy is discussed.The output power of a single TENG unit is relatively low,which cannot meet the demand for high power.Thus,the networking strategy of large-scale TENG is further introduced.TENG’s energy comes from water waves,and each TENG’s output has great randomness,which is very unfavorable for the energy storage after large-scale TENG integration.On this basis,this paper discusses the power management methods of TENG.In addition,in order to further prove its economic and environmental advantages,the economic benefits of TENG are also evaluated.Finally,the development potential of TENG in the field of blue energy and some problems that need to be solved urgently are briefly summarized.

Scalable rolling-structured triboelectric nanogenerator with high power density for water wave energy harvesting toward marine environmental monitoring

In the context of advocating a green and low-carbon era,ocean energy,as a renewable strategic resource,is an important part of planning and building a new energy system.Triboelectric nanogenerator(TENG)arrays provide feasible and efficient routes for large-scale harvesting of ocean energy.In previous work,a spherical rolling-structured TENG with three-dimensional(3D)electrodes based on rolling motion of dielectric pellets was designed and fabricated for effectively harvesting low-frequency water wave energy.In this work,the external shape of the scalable rolling-structured TENG(SR-TENG)and internal filling amount of pellets were mainly optimized,achieving an average power density of 10.08 W∙m^(−3)under regular triggering.In actual water waves,the SR-TENG can deliver a maximum peak power density of 80.29 W∙m^(−3)and an average power density of 6.02 W∙m^(−3),which are much greater than those of most water wave-driven TENGs.Finally,through a power management,an SR-TENG array with eight units was demonstrated to successfully power portable electronic devices for monitoring the marine environment.The SR-TENGs could promote the development and utilization of ocean blue energy,providing a new paradigm for realizing the carbon neutrality goal.

Chain-flip plate triboelectric nanogenerator arranged longitudinally under water for harvesting water wave energy

Triboelectric nanogenerator(TENG)is a new cost-effective blue energy harvesting technology for its great performance in low frequency.However,many related energy harvesters operate on water surface,ignoring the ocean’s depth.Herein,a chainflipped plate TENG(CFP-TENG),consisting of longitudinally arranged repeating units,is proposed to collect wave energy.The chain structure design allows the surface wave energy to act effectively on the underwater generator.The maximum output power per unit ocean area reaches 1.5 W·m^(-2) at a loading resistance of 30 MΩ.Optimization of device parameters and application demonstrations are explored.Compared with previous works,the utilization rate of wave energy has been significantly improved.This work not only provides a new method to optimize the output of TENG but also makes a crucial step in promoting practical applications of TENG in renewable blue energy.

Mechanoluminescent hybrids from a natural resource for energy-related applications

Mechanoluminescent(ML)materials that directly convert mechanical energy into photon emission have emerged as promising candidates for various applications.Despite the recent advances in the development of both novel and conventional ML materials,the limited access to ML materials that simultaneously have the attributes of high brightness,low cost,self-recovery,and stability,and the lack of appropriate designs for constructing ML devices represent significant challenges that remain to be addressed to boost the practical application of ML materials.Herein,ML hybrids derived from a natural source,waste eggshell,with the aforementioned attributes are demonstrated.The introduction of the eggshell not only enables the preparation of the hybrid in a simple and cost-effective manner but also contributes to the homochromatism(red,green,or blue emission),high brightness,and robustness of the resultant ML hybrids.The significant properties of the ML hybrids,together with the proposed structural design,such as porosity or core–shell structure,could expedite a series of mechanic-optical applications,including the self-luminous shoes for the conversion of human motions into light and light generators that efficiently harvest water wave energy.The fascinating properties,versatile designs,and the efficient protocol of“turning waste into treasure”of the ML hybrids represent significant advances in ML materials,promising a leap to the practical applications of this flouring material family.

Development, applications, and future directions of triboelectric nanogenerators

Since the invention of the triboelectric nanogenerator （TENG） in 2012, it has become one of the most vital innovations in energy harvesting technologies. The TENG has seen enormous progress to date, particularly in applications for energy harvesting and self-powered sensing. It starts with the simple working principles of the triboelectric effect and electrostatic induction, but can scavenge almost any kind of ambient mechanical energy in our daily life into electricity. Extraordinary output performance optimization of the TENG has been achieved, with high area power density and energy conversion efficiency. Moreover, TENGs can also be utilized as self-powered active sensors to monitor many environmental parameters. This review describes the recent progress in mainstream energy harvesting and self-powered sensing research based on TENG technology. The birth and development of the TENG are introduced, following which structural designs and performance optimizations for output performance enhancement of the TENG are discussed. The major applications of the TENG as a sustainable power source or a self-powered sensor are presented. The TENG, with rationally designed structures, can convert irregular and mostly low-frequency mechanical energies from the environment, such as human motion, mechanical vibration, moving automobiles, wind, raindrops, and ocean waves. In addition, the development of self-powered active sensors for a variety of environmental simulations based on the TENG is presented. The TENG plays a great role in promoting the development of emerging Internet of Things, which can make everyday objects connect more smartly and energy- efficiently in the coming years. Finally, the future directions and perspectives of the TENG are outlined. The TENG is not only a sustainable micro-power source for small devices, but also serves as a potential macro-scale generator of power from water waves in the future.

Recent progress on the smart membranes based on two-dimensional materials

Inspired by the biosystems,the artificial smart membrane to control the mass transport and molecular conversion has attracted increasing attention in the fields of membrane separation,desalination,nanofiltration,healthcare and environmental remediation.However,the trade-off limitations in polymeric membranes greatly hinder the development of smart membranes with high permeability and manipulability.Recently,inspired by the unique physical/chemical properties of two-dimensional(2 D)materials,2 D materials-based smart membranes(2 DSMs)with the ability of intelligent regulation under different stimuli are highly suitable for membrane applications.According to the desired properties,the 2 DSMs with abundant functional groups can be designed through chemical modification to change the original properties and obtain tunable interlayer spacings under different external conditions.In this review,we summarize the recent progress on artificial smart membranes based on 2 D materials.The design concept and fabrication strategy of 2 DSMs are first introduced.Following that,the developed 2 DSMs are introduced and classified by the type of responsive stimuli,including p H,magnetic field,electric field,light and temperature.Then,the 2 DSMs exhibiting unique performances as membrane separation,pressure sensors,blue energy harvesting,photoelectrochemical sensors and biomimetic devices are presented.Finally,the perspectives and challenges in the developments of 2 DSMs are discussed.