Recentadvancesincarbon‐basedmaterials for solar‐driven interfacial photothermal conversion water evaporation:Assemblies,structures,applications,and prospective

The shortage of fresh water in the world has brought upon a serious crisis to human health and economic development.Solar‐driven interfacial photothermal conversion water evaporation including evaporating seawater,lake water,or river water has been recognized as an environmentally friendly process for obtaining clean water in a low‐cost way.However,water transport is restricted by itself by solar energy absorption capacity's limits,especially for finite evaporation rates and insufficient working life.Therefore,it is important to seek photothermal conversion materials that can efficiently absorb solar energy and reasonably design solar‐driven interfacial photothermal conversion water evaporation devices.This paper reviews the research progress of carbon‐based photothermal conversion materials and the mechanism for solar‐driven interfacial photothermal conversion water evaporation,as well as the summary of the design and development of the devices.Based on the research progress and achievements of photothermal conversion materials and devices in the fields of seawater desalination and photothermal electric energy generation in recent years,the challenges and opportunities faced by carbon‐based photothermal conversion materials and devices are discussed.The prospect of the practical application of solar‐driven interfacial photothermal conversion evaporation technology is foreseen,and theoretical guidance is provided for the further development of this technology.

Simulation-Guided Design of Bamboo Leaf-Derived Carbon-Based High-Efficiency Evaporator for Solar-Driven Interface Water Evaporation

Solar interface water evaporation has been demonstrated to be an advanced method for freshwater production with high solar energy utilization.The development of evaporators with lower cost and higher efficiency is a key challenge in the manufacture of practical solar interface water evaporation devices.Herein,a bamboo leaf-derived carbon-based evaporator is designed based on the light trace simulation.And then,it is manufactured by vertical arrangement and carbonization of bamboo leaves and subsequent polyacrylamide modification.The vertically arranged carbon structure can extend the light path and increase the light-absorbing area,thus achieving excellent light absorption.Furthermore,the continuous distribution of polyacrylamide hydrogel between these vertical carbons can support high-speed water delivery and shorten the evaporation path.Therefore,this evaporator exhibits an ultrahigh average light absorption rate of~96.1%,a good water evaporation rate of 1.75 kg m^(-2) h^(-1),and an excellent solar-to-vapor efficiency of 91.9%under one sun irradiation.Furthermore,the device based on this evaporator can effectively achieve seawater desalination,heavy metal ion removal,and dye separation while completing water evaporation.And this device is highly available for actual outdoor applications and repeated recycling.

Composite laminar membranes for electricity generation from water evaporation

Harvesting clean energy from water evaporation has been extensively investigated due to its sustainability.To achieve high efficiency,energy conversion materials should contain multiple features which are difficult to be simultaneously obtained from single-component materials.Here we use composite laminar membranes assembled by nanosheets of graphene oxide and mica,and find a sustained power density induced by water evaporation that is two orders of magnitude larger than that from membranes made by either of the components.The power output is attributed to selective proton transport driven by water evaporation through the interlayer nanochannels in the membranes.This process relies on the synergistic effects from negatively charged and hydrophilic mica surfaces that are important for proton selectivity and water transport,and the tunable electrical conductivity of graphene oxide that provides optimized internal resistance.The demonstrated composite membranes offer a strategy of enhancing power generation by combining the advantages from each of their components.

Hybrid hydrovoltaic electricity generation driven by water evaporation

Water evaporation is a ubiquitous natural process exploiting thermal energy from ambient environment.Hydrovoltaic technologies emerged in recent years offer one prospective route to generate electricity from water evaporation,which has long been overlooked.Herein,we developed a hybrid hydrovoltaic generator driven by natural water evaporation,integrating an“evaporation motor”with an evaporation-electricity device and a droplet-electricity device.A rotary motion of the“evaporation motor”relies on phase change of ethanol driven by water-evaporation induced temperature gradient.This motion enables the evaporation-electricity device to work under a beneficial water-film operation mode to produce output of~4 V and~0.2μA,as well as propels the droplet-electricity device to convert mechanical energy into pulsed output of~100 V and~0.2 mA.As different types of hydrovoltaic devices require distinctive stimuli,it was challenging to make them work simultaneously,especially under one single driving force.We here for the first time empower two types of hydrovoltaic devices solely by omnipresent water evaporation.Therefore,this work presents a new pathway to exploiting water evaporation-associated ambient thermal energy and provides insights on developing hybrid hydrovoltaic generators.

Constructing central hollow cylindrical reduced graphene oxide foams with vertically and radially orientated porous channels for highly efficient solar-driven water evaporation and purification

Although solar steam generation is an eco-friendly approach for desalinating seawater and purifying wastewater,there are still issues on how to improve the efficiency of solar energy utilization and accelerate the water and heat transport inside the solardriven water evaporators.Herein,we design a central hollow cylindrical reduced graphene oxide(RGO)foam with vertically and radially orientated channels as a solar steam generation device for efficient water evaporation and purification.The vertically aligned porous channels accelerate upward transport of water to the top evaporation surface,while the radially aligned porous channels facilitate water transport and heat transfer along the radial directions for fully utilizing the heat accumulated inside the central cylindrical hole of the foam.The central hole of the foam plays a highly positive role in accumulating more heat for accelerating the water evaporation,the newly generated inner sidewall resulted from the central hole can gain extra thermal energy from surrounding environment in the same way as the outer sidewall of the foam due to the surface cooling effect of the water evaporation.As a result,the vertically and radially aligned RGO foam evaporator with central hollow cylinder achieves a high solar steam generation rate of 2.32 kg·m^(−2)·h^(−1)with an exceptional energy conversion efficiency of 120.9%under 1-sun irradiation,superior to the vertically aligned RGO foam without the central hole(1.83 kg·m^(−2)·h^(−1),96.9%)because of the enhanced water and heat transfer inside the porous channels,the efficient utilization of environmental energy.

Integrating reduced graphene oxides and PPy nanoparticles for enhanced electricity from water evaporation

Developing high-performance nanostructured materials is key to deliver the potential of hydrovoltaic technology into practical applications.As single-component materials have approached its limit in generating hydrovoltaic electricity,the development of multi-component hydrovoltaic materials has been necessary in continuously boosting the electricity output.Here,we report a hydrovoltaic material by integrating reduced graphene oxides and polypyrrole nanoparticles(rGO/PPy),where the rGO contributes improved conductivity and large specific surface area while PPy nanoparticles enable enhanced interaction with water.The device fabricated with this material generates a short-circuit current of 6μA as well as a maximum power density of over 1μW/cm3 from natural evaporation of water.And the substantial ion-PPy interaction enables robust voltage generation from evaporation of various salt solutions.Moreover,an outstanding scaling ability is demonstrated by connecting 10 devices in series that generate a sustainable voltage of up to~2.5 V,sufficing to power many commercial devices,e.g.LED bulb and LCD screen.

Facile preparation of multifunctional Cu_(2−x)S/S/rGO composite for all-round residual water remediation during interfacial solar driven water evaporation process

Presently,interfacial solar water evaporation(ISWE)is now injecting new vitality into the field of water remediation.However,during the ISWE process,the nonvolatile pollutants might be concentrated in residual water,and further contaminate the environment.Preparing advanced photothermal materials is in need to get comprehensive purification of various pollutants in residual water.Herein,we report a facile laser thermal method to prepare Cu_(2−x)S/sulfur/reduced graphene oxide(Cu_(2−x)S/S/rGO)nanocomposites for realizing all-round residual water remediation during the ISWE process.The as-prepared Cu2−xS/S/rGO nanocomposites demonstrated excellent photothermal and photocatalytic properties.Through blending with GO nanosheets having excellent adsorption capacity,the synergetic effect of photothermal,photocatalytic,and adsorption properties resulted in highly efficient purification of rhodamine B,bacterial,and heavy metal ions in residual water during the ISWE process.The experimental results also showed that,increasing solar light intensity can promote the residual water remediation,but ultrafast water evaporation under high light intensity may deteriorate the purifying effect.This report may pave a new way to prepare multifunctional materials for water remediation through the ISWE technology.

Analysis of evaporation of high-salinity phreatic water at a burial depth of 0 m in an arid area

High-salinity phreatic water refers to which with total dissolved solids（TDS）>30 g/L. Previous studies have shown that high salinity phreatic water evaporation is different at different depths. High salinity phreatic water evaporation under 0 m depth is the basis of the high salinity phreatic water evaporation studies. In this study, evaporation of high-salinity phreatic water at a burial depth of 0 m in arid area was investigated. New insights were gained on evaporation mechanisms via experiments conducted on high-salinity phreatic water with TDS of 100 g/L at 0 m at the study site at Changji Groundwater Balance Experiment Site, Xinjiang Uygur Autonomous Region in China, where the lithology of the vadose（unsaturated zone） was silty clay. Comparison was made on the data of high-salinity phreatic water evaporation, water surface evaporation(EΦ20) and meteorological data obtained in two complete hydrological years from April 1, 2012 to March 31, 2014. The experiments demonstrated that when the lithology of the vadose zone is silty clay, the burial depth is 0 m and the TDS is 100 g/L, intra-annual variation of phreatic water evaporation is the opposite to the variation of atmospheric evaporation EΦ20 and air temperature. The salt crust formed by the evaporation of high-salinity phreatic water has a strong inhibitory effect on phreatic water evaporation. Large volumes of precipitation can reduce such an inhibitory effect. During freezing periods, surface snow cover can promote the evaporation of high-salinity phreatic water at 0 m; the thicker the snow cover, the more apparent this effect is.

In situ Reduction of Silver Nanoparticles on Chitosan Hybrid Copper Phosphate Nanoflowers for Highly Efficient Plasmonic Solar-driven Interfacial Water Evaporation

The development of water purification device using solar energy has received tremendous attention.Despite extensive progress,traditional photothermal conversion usually has a high cost and high environmental impact.To overcome this problem,we develop a low cost,durable and environmentally friendly solar evaporator.This bilayered evaporator is constructed with a thermal insulating polyvinylidene fluoride(PVDF)membrane as a bottom supporting layer and plasmonic silver nanoparticles decorated miero-sized hybrid flower(Ag/MF)as a top light-to-heat conversion layer.Compared with the sample with a flat silver film,the two-tier Ag/MF has a plasmonic enrichment property and high efficiency in converting the solar light to hcat as cach flower can gencrate a microscale hotspot by enriching the absorbed solar light.On the other hand,the PVDF membrane on the bottom with porous structure not only improves the mechanicalstability of the entire structure,but also maintains a stable water supply from the bulk water to the evaporation interface by capillarity and minimizes the thermal conduction.The combination of excellent water evaporation ability simple operation,and low cost of the production process imparts this type of plasmonic enhanced solar-driven interfacial water evaporator with promising prospects for potable water purification for point-of-use applications.

Effects of mixed-based biochar on water infiltration and evaporation in aeolian sand soil

Aeolian sandy soil in mining areas exhibits intense evaporation and poor water retention capacity.This study was designed to find a suitable biochar application method to improve soil water infiltration and minimize soil water evaporation for aeolian sand soil.Using the indoor soil column method,we studied the effects of three application patterns(A(0-20 cm was a mixed sample of mixed-based biochar and soil),B(0-10 cm was a mixed sample of mixed-based biochar and soil and 10-20 cm was soil),and C(0-10 cm was soil and 10-20 cm was a mixed sample of mixed-based biochar and soil)),four application amounts(0%(control,CK),1%,2%,and 4%of mixed-based biochar in dry soil),and two particle sizes(0.05-0.25 mm(S1)and<0.05 mm(S2))of mixed-based biochar on water infiltration and evaporation of aeolian sandy soil.We separately used five infiltration models(the Philip,Kostiakov,Horton,USDA-NRCS(United States Department of Agriculture-Natural Resources Conservation Service),and Kostiakov-Lewis models)to fit cumulative infiltration and time.Compared with CK,the application of mixed-based biochar significantly reduced cumulative soil water infiltration.Under application patterns A,B,and C,the higher the application amount and the finer the particle size were,the lower the migration speed of the wetting front.With the same application amount,cumulative soil water infiltration under application pattern A was the lowest.Taking infiltration for 10 min as an example,the reductions of cumulative soil water infiltration under the treatments of A2%(S2),A4%(S1),A4%(S2),A1%(S1),C2%(S1),and B1%(S1)were higher than 30%,which met the requirements of loess soil hydraulic parameters suitable for plant growth.The five infiltration models well fitted the effects of the treatments of application pattern C and S1 particle size(R2>0.980),but the R2 values of the Horton model exceeded 0.990 for all treatments(except for the treatment B2%(S2)).Compared with CK,all other treatments reduced cumulative soil water infiltration,except for B4%(S2).With the same application amount,cumulative soil water evaporation difference between application patterns A and B was small.Treatments of application pattern C and S1 particle size caused a larger reduction in cumulative soil water evaporation.The reductions in cumulative soil water evaporation under the treatments of C4%(S1),C4%(S2),C2%(S1),and C2%(S2)were over 15.00%.Therefore,applying 2%of mixed-based biochar with S1 particle size to the underlying layer(10-20 cm)could improve soil water infiltration while minimizing soil water evaporation.Moreover,application pattern was the main factor affecting soil water infiltration and evaporation.Further,there were interactions among the three influencing factors in the infiltration process(application amount×particle size with the most important interaction),while there were no interactions among them in the evaporation process.The results of this study could contribute to the rational application of mixed-based biochar in aeolian sandy soil and the resource utilization of urban and agricultural wastes in mining areas.

Estimation of evaporation losses based on stable isotopes of stream water in a mountain watershed

Water stable isotopes(δ^(2) H andδ^(18)O)can record surface water evaporation,which is an important hydrological process for understanding watershed structure and function evolution.However,the isotopic estimation of water evaporation losses in the mountain watersheds remains poorly explored,which hinders understanding spatial variations of hydrological processes and their relationships with the temperature and vegetation.Here we investigatedδ^(2) H,δ^(18)O,and d-excess values of stream water along an altitude gradient of 2130 to 3380 m in Guan’egou mountain watershed at the east edge of the Qinghai-Tibet Plateau in China.The meanδ^(2) H(-69.6‰±2.6‰),δ^(18)O(-10.7‰±0.3‰),and dexcess values(16.0‰±1.4‰)of stream water indicate the inland moisture as the major source of precipitation in study area.Water stable isotopes increase linearly with decreasing altitudes,based on which we estimated the fractions of water evaporation losses along with the altitude and their variations in different vegetations.This study provides an isotopic evaluation method of water evaporation status in mountain watersheds,the results are useful for further understanding the relationship between hydrological processes and ecosystem function under the changing climate surrounding the Qinghai-Tibet Plateau.

Stable Isotopes and Chloride Applied as Soil Water Tracers for Phreatic Evaporation Experiment

A phreatic water evaporation experiment,without rainfall influence,was designed to study the mechanisms of soil water movement through groundwater recharge to the unsaturated zone. Soil moisture content,chloride concentration,and δD and δ~18 O values of soil water were measured. Results showthat with decreasing soil moisture content,the chloride concentration of leachate( ρ_f(Cl)) in the capillary water layer decreases,whereas the ρ_f(Cl) value of the hanging and film water layers above the capillary water layer increases. With the combined δD and δ~18 O values,the soil water in the hanging and film water layers is influenced by evaporation,although a dry sand layer of 39 cm exists above the wet sand layer. The highest evaporation rate and the largest salt accumulation occur at a depth of about 39 cm in columns d,e,and f(Six polyvinyl chloride columns were assigned as column a,b,c,d,e,and f). We deduce that soil water migrates in the form of liquid water above the capillary water layer. In the experiment,a part of phreatic water consumed is used for the movement of soil water,whereas the other part is lost to evaporation. Soil water could continue migrating upward with prolonged experiment duration.

Evaporation of nanoscale water on solid surfaces

The evaporation of water is essential in the macroscopic world.Recent researches show that,on solid surfaces,the evaporation of nanoscale water is quite different from that on bulk water surfaces.In this review,we show the theoretical progress in the study of nanoscale water evaporation on various solid surfaces:the evaporation rate of nanoscale water does not show a monotonic decrease when the solid surface changes from hydrophobic to hydrophilic;the evaporation of nanoscale water on hydrophobic-hydrophilic patterned surfaces is unexpectedly faster than that on uniform surface;the evaporation of nanoscale water on patterned graphene oxide is faster than that on homogeneous one;how temperature affects the evaporation of nanoscale water on solid surface;how ions affect the evaporation of nanoscale water on graphene oxide.

Self-Healing Hydrophilic Porous Photothermal Membranes for Durable and Highly Efficient Solar-Driven Interfacial Water Evaporation

It is highly desirable to develop a solar-driven interfacial water evaporatorwith a self-healing ability and high-efficiency water evaporation performance for water distillation and desalination;however,this process is considerably challenging.Herein,by exploiting the advantages of a self-healing hydrophilic polymer,a self-healing hydrophilic porous photothermal(SHPP)membrane was fabricated by curing a mixture of the polymer,carbon black,and NaCl,followed by removal of the NaCl from water.Since the SHPP membrane could serve as a photothermal layer and water transportation channel simultaneously,a solar-driven interfacial evaporator could be fabricated readily by assembling the SHPP membrane with polyethylene foam.We have shown that the SHPP membrane-based evaporator exhibited a water evaporation rate of 1.68 kg m^(−2) h^(−1) and an energy efficiency of 97.3%.These values are superior to those obtained using solar-driven interfacial evaporators with self-healing capability.Notably,by hydrogen bonds reformation between the fracture surfaces,the SHPP membrane could regain its structural integrity after breaking,making the SHPPmembrane-based evaporator the first to heal entirely and repeatedly from physical damage to sustain itswater evaporation capacity.Therefore,the potential of using SHPP membranes to develop stable,long-last ing,andhigh-efficiency solar-driven interfacial water evaporators is highlighted.

Janus membrane with enhanced interfacial activation for solar evaporation

Low solar spectrum coverage,high evaporation enthalpy,and undesired salt deposition severely limited the solar-driven interfacial evaporation technology for further sewage purification and seawater desalination.To overcome these problems,we designed an amphiphilic Janus-structured polyaniline(PANI)/ZrC/cellulose acetate(CA)(J-PZCA) membrane.Firstly,the interfacial interaction between PANI and ZrC enhances the photoabsorption and photothermal conversion efficiency.Secondly,low thermal conductivity reduces the heat lost at the interface.Most importantly,ZrC could facilitate interfacial activation,which weakens the intermolecular forces of water by affecting the hydrogen bond.Under 1 solar irradiation(1 sun),the composite membrane exhibits a high evaporation rate of 1.31 kg m^(-2)h^(-1) and an excellent efficiency of 79.4%.In addition,the sewage purification and seawater desalination experiments reveal a remarkable purification capability of J-PZCA membrane.Especially for the treatment of high-concentration salt solution,it realizes a long-term stable evaporation performance due to the excellent salt deposition resistance.Therefore,the J-PZCA membrane constructed in this study provides a new perspective for the design of efficient interfacial evaporation devices.

Effect of climate change on the trends of evaporation of phreatic water from bare soil in Huaibei Plain, China

When the soil condition and depth to water table stay constant, climate condition will then be the only determinant of evaporation intensity of phreatic water from bare soil. Based on a series of long-term quality-controlled data collected at the Wudaogou Hydrological Experiment Station in the Huaibei Plain, Anhui, China, the variation trends of the evaporation rate of phreatic water from bare soil were studied through the Mann-Kendall trend test and the linear regression trend test, followed by the study on the responses of evaporation to climate change. Results indicated that in the Huaibei Plain during 1991-2008, evaporation of phreatic water from bare soil tended to increase at a rate of 5% on monthly scale in March, June and July while in other months the increase was minor. On the seasonal basis, the evaporation saw significant increase in spring and summer. In addition, annual evaporation tended to grow evidently over time. When air temperature rises by 1 °C, the annual evaporation rate increases by 7.24–14.21%, while when the vapor pressure deficit rises by 10%, it changes from-0.09 to 5.40%. The study also provides references for further understanding of the trends and responses of regional evapotranspiration to climate change.

A hierarchical salt-rejection strategy for sustainable and high-efficiency solar-driven desalination

Solar steam generation(SSG)is widely regarded as one of the most sustainable technologies for seawater desalination.However,salt fouling severely compromises the evaporation performance and lifetime of evaporators,limiting their practical applications.Herein,we propose a hierarchical salt-rejection(HSR)strategy to prevent salt precipitation during long-term evaporation while maintaining a rapid evaporation rate,even in high-salinity brine.The salt diffusion process is segmented into three steps—insulation,branching diffusion,and arterial transport—that significantly enhance the salt-resistance properties of the evaporator.Moreover,the HSR strategy overcomes the tradeoff between salt resistance and evaporation rate.Consequently,a high evaporation rate of 2.84 kg m^(-2) h^(-1),stable evaporation for 7 days cyclic tests in 20 wt%NaCl solution,and continuous operation for 170 h in natural seawater under 1 sun illumination were achieved.Compared with control evaporators,the HSR evaporator exhibited a>54%enhancement in total water evaporation mass during 24 h continuous evaporation in 20 wt%salt water.Furthermore,a water collection device equipped with the HSR evaporator realized a high water purification rate(1.1 kg m^(-2) h^(-1)),highlighting its potential for agricultural applications.

Fabrication of stable MWCNT bucky paper for solar-driven interfacial evaporation by coupling c-ray irradiation with borate crosslinking

Herein,we report a facile solution process for preparing multi-walled carbon nanotube(MWCNT)bucky paper for solar-driven interfacial water evaporation.This process involves vacuum filtrating a dispersion of MWCNTs that was modified by polyvinyl alcohol(PVA)under c-ray irradiation on a cellulose acetate microporous membrane,followed by borate crosslinking.Fourier transform infrared spectroscopy,Raman spectroscopy,and thermogravimetry confirmed the success of PVA grafting onto MWCNTs and borate crosslinking between modified MWCNT nanoyarns.The as-prepared crosslinked MWCNT bucky papers(BBP membranes)were used as a solar absorber,by placing them on a paper-wrapped floating platform,for interfacial water evaporation under simulated solar irradiation.The BBP membranes showed good water tolerance and mechanical stability,with an evaporation rate of 0.79 kg m^(-2)h^(-1)and an evaporation efficiency of 56%under 1 sun illumination in deionized water.Additionally,the BBP membranes achieved an evaporation rate of 0.76 kg m^(-2)h^(-1)in both NaCl solution(3.5 wt%)and sulfuric acid solution(1 mol L-1),demonstrating their impressive applicability for water reclamation from brine and acidic conditions.An evaporation rate of 0.70 kg m-2 h-1(very close to that from deionized water)was obtained from the solar evaporation of saturated NaCl solution,and the BBP membrane exhibited unexpected stability without the inference of salt accumulation on the membrane surface during long-term continuous solar evaporation.

Evaporation Retardation by Monomolecular Layers: An Experimental Study at the Aji Reservoir (India)

It is an established fact that huge quantities of water are lost from lakes, reservoirs and soils by evaporation. This assumes greater significance in arid and semi-arid regions around the globe when a general scarcity of water is compounded by high evaporation loss from the open water surfaces of lakes and reservoirs. The use of surface covering by a monomolecular film to reduce evaporation loss from large open water surfaces offers the greatest promise among all currently available techniques. This is the only system that retains the water surface in a state that does not interfere with other uses of the body of water such as boating, navigation recreation, fish, and wildlife propagation. Various experiments and field trials worldwide have proven conclusively that the fatty alcohols and their emulsions effectively retard water evaporation and result in saving to the tune of about 20% to 50%. An experiment was carried out at the Aji Reservoir (India) using a mixture of Cetyl and Stearyl alcohol that confirmed 19.26% saving in evaporation loss. During this six-month trial, about 0.18 mcum of water was saved which otherwise might have evaporated.

Designing high-efficiency light-to-thermal conversion materials for solar desalination and photothermal catalysis

Light-to-thermal conversion materials(LTCMs)have been of great interest to researchers due to their impressive energy conversion capacity and wide range of applications in biomedical,desalination,and synergistic catalysis.Given the limited advances in existing materials(metals,semiconductors,π-conjugates),researchers generally adopt the method of constructing complex systems and hybrid structures to optimize performance and achieve multifunctional integration.However,the development of LTCMs is still in its infancy as the physical mechanism of light-to-thermal conversion is unclear.In this review,we proposed design strategies for efficient LTCMs by analyzing the physical process of light-tothermal conversion.First,we analyze the nature of light absorption and heat generation to reveal the physical processes of light-to-thermal conversion.Then,we explain the light-to-thermal conversion mechanisms of metallic,semiconducting andπ-conjugated LCTMs,and propose new material design strategies and performance improvement methods.Finally,we summarize the challenges and prospects of LTCMs in emerging applications such as solar water evaporation and photothermal catalysis.