Photothermal materials for efficient solar powered steam generation

Solar powered steam generation is an emerging area in the field o f energy harvest and sustainable technologies.The nano-structured photothermal materials are able to harvest energy from the full solar spectrum and convert it to heat with high efficiency.Moreover,the materials and structures for heat management as well as the mass transportation are also brought to the forefront.Several groups have reported their materials and structures as solutions for high performance devices,a few creatively coupled other physical fields with solar energy to achieve even better results.This paper provides a systematic review on the recent developments in photothermal nanomaterial discovery,material selection,structural design and mass/heat management,as well as their applications in seawater desalination and fresh water production from waste water with free solar energy.It also discusses current technical challenges and likely future developments.This article will help to stimulate novel ideas and new designs for the photothermal materials,towards efficient,low cost practical solar-driven clean water production.

Towards highly salt-rejecting solar interfacial evaporation:Photothermal materials selection,structural designs,and energy management

With the development of the industry,water pollution and shortage have become serious global problems.Owing to the abundance of seawater storage on earth,efficient solar-driven evaporation is a promising approach to relieve the freshwater shortage.The solar-driven evaporation has attracted tremendous attention due to its potential application in the seawater desalination and wastewater treatment fields.Also,the solar-driven evaporation efficiency can be enhanced by designing both solar absorbers and structures.Up to now,many strategies have been explored to achieve high solar-driven evaporation efficiency,mainly including the selection of photothermal conversion materials and structure optimization.In this review,the solar absorbers,structural designs,and energy management are proposed as the keys for high performance solar-driven evaporation systems.We report four kinds of solar absorbers based on different photothermal conversion mechanisms,substrate structure designs,and energy management methods for the purpose to achieve high conversion efficiency.And we also systematically investigate the available salt-rejections strategies for seawater desalination.This review aims to summarize the current development of efficient solar-driven evaporation systems and provide insights into the photothermal conversion materials,structural designs,and energy management.Finally,we propose the perspectives of the salt-rejection technologies for seawater desalination.

Nitrogen-doped microporous graphite-enhanced copper plasmonic effect for solar evaporation

Water scarcity is a global challenge,and solar evaporation technology offers a promising and eco-friendly solution for freshwater production.Photothermal conversion materials(PCMs)are crucial for solar evaporation.Improving photothermal conversion efficiency and reducing water evaporation enthalpy are the two key strategies for the designing of PCMs.The desired PCMs that combine both of these properties remain a challenging task,even with the latest advancements in the field.Herein,we developed copper nanoparticles(NPs)with different conjugated nitrogen-doped microporous carbon coatings(Cu@C–N)as PCMs.The microporous carbon enveloping layer provides a highly efficient pathway for water transport and a nanoconfined environment that protects Cu NPs and facilitates the evaporation of water clusters,reducing the enthalpy of water evaporation.Meanwhile,the conjugated nitrogen nodes form strong metal-organic coordination bonds with the surface of copper NPs,acting as an energy bridge to achieve rapid energy transfer and provide high solar-to-vapor conversion efficiency.The Cu@C–N exhibited up to 89.4%solar-to-vapor conversion efficiency and an evaporation rate of 1.94 kgm^(−2) h^(−1) under one sun irradiation,outperforming conventional PCMs,including carbon-based materials and semiconductor materials.These findings offer an efficient design scheme for high-performance PCMs essential for solar evaporators to address global water scarcity.

Boosting extraction of Pb in contaminated soil via interfacial solar evaporation of multifunctional sponge

Interfacial solar water evaporation is a reliable way to accelerate water evaporation and contaminant remediation.Embracing the recent advance in photothermal technology,a functional sponge was prepared by coating a sodium alginate(SA)impregnated sponge with a surface layer of reduced graphene oxide(rGO)to act as a photothermal conversion medium and then subsequently evaluated for its ability to enhance Pb extraction from contaminated soil driven by interfacial solar evaporation.The SA loaded sponge had a Pb adsorption capacity of 107.4 mg g^(-1).Coating the top surface of the SA sponge with rGO increased water evaporation performance to 1.81 kg m^(-2)h^(-1)in soil media under one sun illumination and with a wind velocity of 2 m s^(-1).Over 12 continuous days of indoor evaporation testing,the Pb extraction efficiency was increased by 22.0%under 1 sun illumination relative to that observed without illumination.Subsequently,Pb extraction was further improved by 48.9%under outdoor evaporation conditions compared to indoor conditions.Overall,this initial work shows the significant potential of interfacial solar evaporation technologies for Pb contaminated soil remediation,which should also be applicable to a variety of other environmental contaminants.

Size-controlled synthesis and near-infrared photothermal response of Cp^(*)Rh-based metalla[2]catenanes and rectangular metallamacrocycles

A variety of research reports on novel supramolecular topologies have been published over the last years.However,it is still a great challenge to tap into the inner functional properties of these complexes.Herein,two tetranuclear metallamacrocycles 1 and 2 and four octonuclear[2]catenanes 3-6 were constructed successfully via a coordination-driven self-assembly strategy,by conscious design and use of the tetramethyl bidentate pyridine ligand L1,and the appropriate selection of six binuclear half-sandwich rhodium building units with different longitudinal dimensions.The complexes have been fully characterized by single crystal X-ray diffraction analysis and NMR spectroscopy.Furthermore,near-infrared photothermal studies of the obtained[2]catenanes reveal different photothermal response in solid and solution states,which may be attributed to a strong fluorescence quenching effect of the half-sandwich organometallic fragment and different conjugated effect of Cp^(*)Rh based building blocks in the interlocking structures.The photothermal conversion efficiencies of[2]catenanes 4-6 fall in the range 30.5%-16.5% respectively.This contribution aims to play a key role in the experimental development of Cp^(*)-based photothermal materials.

Simultaneous Solar-driven Steam and Electricity Generation by Cost-effective,Easy Scale-up MnO 2-based Flexible Membranes

Harvesting solar energy in an effective manner for steam and electricity generation is a promising technique to simultaneously cope with the energy and water crises.However,the construction of efficient and easy scale-up photothermal materials for steam and electricity cogeneration remains challenging.Herein,we report a facile and cost-effective strategy to prepare MnO_(2)-decorated cotton cloth(MCx).The wide adsorption spectrum and excellent photothermal conversion ability of the in situ-formed MnO_(2)nanoparticles make the MCx to be advanced photothermal materials.Consequently,the hybrid device integrated with MCx as the photothermal layer and the thermoelectric(TE)module for electricity power conversion exhibits an extremely high evaporation rate of 2.24 kg m^(−2)h^(−1)under 1 kW m^(−2)irradiation,which is ranked among the most powerful solar evaporators.More importantly,during solar evaporation,the hybrid device produces an open-circuit voltage of 0.3 V and a power output of 1.6 W m^(−2)under 3 Sun irradiation,and outperforms most of the previously reported solar-driven electricity generation devices.Therefore,the integrated device with synergistic solar-thermal utilization opens up a green way toward simultaneous solar vapor and electric power generation in remote and resource-constrained areas.

A cobalt oxide@polydopamine-reduced graphene oxide-based 3D photothermal evaporator for highly efficient solar steam generation

Improving the evaporation rate and energy efficiency of solar steam generation is very important to facilitate real-world applications for clean water production.In this work,Co_(3)O_(4)@polydopamine(PDA)nanoparticles were synthesized and combined with reduced graphene oxide(rGO)to fabricate a new Co_(3)O_(4)@PDA-rGO photothermal aerogel.The obtained pho-tothermal aerogel sheet was thereafter used to prepare both two-dimensional(2D)and three-dimensional(3D)photothermal evaporators for solar steam generation.Due to the excellent light absorption and hydrophilicity of the photothermal aerogel,a high evaporation rate of 1.60 kg·m^(−2)·h^(−1) was achieved for the 2D photothermal evaporator.While for the 3D evaporator,the evaporation rate was dramatically increased to 3.71 kg·m^(−2)·h^(−1) with a corresponding light-to-vapor energy efficiency of 107%.This was attributed to an increased evaporation surface area,decreased energy loss from the top evaporation surface to the environment,and energy gain from the environment on the side evaporation surface.The 3D evaporator also showed excellent practical performance in seawater desalination thus demonstrating great potential for real-world applications.

Four-birds-with-one-stone:A multifunctional Ti-based material for solar-driven water evaporation

Sustainable,environmentally friendly and low-energy desalination materials have important research value for the increasing demand of freshwater year by year.However,it is a huge challenge to maintain high heat energy transfer efficiency without reducing the heat conversion capacity of specific solar photothermal conversion materials.Moreover,their efficiency and durability are greatly limited by the problems of seawater corrosion,oil,and bacteria pollutions.Till now,no related work has been reported to solve all the aforementioned problems via a simple four-birds-with-one-stone strategy.Herein,a class of multifunctional porous photothermal silver(Ag)modified Ti foams(Tf-TA/Ag series materials)is prepared for the development of advanced solar water evaporation devices,and provides alternative materials for alleviating freshwater crisis and treating sewage.The oil contact angle(OCA)changes from 41°to 180°,which significantly reduces the adhesion of oil.In addition,Tf-TA2/Ag sample also shows an excellent and sustained antibacterial effect,which maintains above 99.9%of antibacterial rate after repeated 5 times.The surface temperature of the Tf-TA2/Ag sample reaches 52.5℃ after simulated sun irradiation for 20 min,which is significantly higher than that of the contact groups(water:36.4℃,Ti foam:38.2℃ and Tf-TA2:40.9℃).The capacity of seawater evaporation and salt removal is enhanced due to the excellent photothermal properties,low reflectance,and uniform heat dissipation pores.The water production efficiency of Tf-TA2/Ag sample is 1.41 kg·m^(-2)·h^(-1) in artificial seawater and 0.76 kg·m^(-2)·h^(-1) in oily sewage under simulated sun irradiation.Furthermore,the hydrophilic and oleophobic properties of Tf-TA2/Ag are critical to extracting water from oil/water mixture in diverse water environments.Ultimately,this four-birds-with-one-stone approach provides a new perspective for the improvement of solar seawater desalination performance.

Nanoporous black silver film with high porosity for efficient solar steam generation

Given the challenges brought by the shortage of freshwater resources,solar water evaporation has been regarded as one of the most promising technologies for harnessing abundant sunlight to harvest clean water from the sea.Nanostructured metals have attracted extensive attention in solar water evaporation due to their localized surface plasmon resonance effect,but highly porous metallic films with high evaporation efficiency are challenging.Herein,a self-supporting black nanoporous silver(NP-Ag)film was fabricated by dealloying of an extremely dilute Al99Ag1 alloy.The choice of the dilute precursor guarantees the formation of the NP-Ag film with high porosity(96.5%)and low density(0.3703 g·cm^(-3),even smaller than the lightest metal lithium).The three-dimensional ligament-channel network structure and the nanoscale(14.6 nm)of ligaments enable the NP-Ag film to exhibit good hydrophilicity and broadband absorption over 200‒2,500 nm.More importantly,the solar evaporator based on the NP-Ag film shows efficient solar steam generation,including the efficiency of 92.6%,the evaporation rate of 1.42 kg·m^(-2)·h^(-1)and good cycling stability under one sun irradiation.Moreover,the NP-Ag film exhibits acceptable seawater desalination property with the ion rejection for Mg^(2+),Ca^(2+),K^(+)and Na^(+)more than 99.3%.Our findings could provide a new idea and inspiration for the design and fabrication of metal-based photothermal films in real solar evaporation applications.

Recent strategies for constructing efficient interfacial solar evaporation systems

Interfacial solar evaporation(ISE)is a promising technology to relieve worldwide freshwater shortages owing to its high energy conversion efficiency and environmentally sustainable potential.So far,many innovative materials and evaporators have been proposed and applied in ISE to enable highly controllable and efficient solar-to-thermal energy conversion.With rational design,solar evaporators can achieve excellent energy management for lowering energy loss,harvesting extra energy,and efficiently utilizing energy in the system to improve freshwater production.Beyond that,a strategy of reducing water vaporization enthalpy by introducing molecular engineering for water-state regulation has also been demonstrated as an effective approach to boost ISE.Based on these,this article discusses the energy nexus in two-dimensional(2D)and three-dimensional(3D)evaporators separately and reviews the strategies for design and fabrication of highly efficient ISE systems.The summarized work offers significant perspectives for guiding the future design of ISE systems with efficient energy management,which pave pathways for practical applications.

An Exceptional Broad-Spectrum Nanobiocide for Multimodal and Synergistic Inactivation of Drug-Resistant Bacteria

This study reports the fabrication of a novel photothermal material formed via the physical blending of excess lauric acid(LA)and cupric acetate,followed by efficient ligand exchange.Surprisingly,the copper–LA complex exhibited a 12-fold enhancement of the molar extinction coefficient in the nearinfrared(NIR)region relative to aqueous cupric acetate.Inspired by this interesting finding,we formulated these photothermal materials into colloidally dispersed nanoparticles via a technique that combined nanoprecipitation and in situ surface polymerization for antibacterial studies.The resultant nanoparticles exhibited rapid and stable photothermal responses to NIR irradiation,with a 4-fold enhanced photothermal conversion efficiency relative to aqueous cupric acetate.Since a positively charged monomer was incorporated during in situ surface polymerization,these positively charged nanoparticles were ingested efficiently and subsequently digested by drug-resistant bacteria.By combining the LA-mediated membrane-damaging effect,copper-mediated Fenton-like reaction,as well as the photothermal effect of the copper–LA complex,a broad-spectrum,multimodal,and synergistic antibacterial effect was achieved both in vitro and in vivo,with the killing efficiency up to 99.99%for ampicillin-resistant Escherichia coli(Ampr E.coli)and 99.9999%for methicillinresistant Staphylococcus aureus(MRSA).Our newly developed nanobiocide represents a class of exceptional broad-spectrum antibacterial materials,holding great potential for treating drug-resistant infections in clinical settings.