Because it is able to produce desalinated water directly using solar energy with minimum carbon footprint, solar steam generation and desalination is considered one of the most important technologies to address the increasingly pressing global water scarcity. Despite tremendous progress in the past few years, efficient solar steam generation and desalination can only be achieved for rather limited water quantity with the assistance of concentrators and thermal insulation, not feasible for large-scale applications. The fundamental paradox is that the conventional design of direct absorber−bulk water contact ensures efficient energy transfer and water supply but also has intrinsic thermal loss through bulk water. Here, enabled by a confined 2D water path, we report an efficient (80% under one-sun illumination) and effective (four orders salinity decrement) solar desalination device. More strikingly, because of minimized heat loss, high efficiency of solar desalination is independent of the water quantity and can be maintained without thermal insulation of the container. A foldable graphene oxide film, fabricated by a scalable process, serves as efficient solar absorbers (>94%), vapor channels, and thermal insulators. With unique structure designs fabricated by scalable processes and high and stable efficiency achieved under normal solar illumination independent of water quantity without any supporting systems, our device represents a concrete step for solar desalination to emerge as a complementary portable and personalized clean water solution.graphene oxide | solar steam | 2D water path | solar desalination | heat localization A s water scarcity (1, 2) becomes one of most pressing global challenges of our time, efficient solar desalination could provide a promising solution to produce clean water directly out of solar energy without extra energy input, particularly urgent for developing countries and remote areas without basic infrastructures (3-5). With rapid development in the past few years (6-16), it is clear that there are two key elements to enable efficient solar desalination: broadband and efficient solar absorption and localized heat management for efficient vapor generation with minimized parasitic thermal loss. So far, significant progress has been made on both of these fronts. Absorbers with various rational designs have been demonstrated with efficient solar absorption (11,14,15). Also, from dispersed particles (6, 7, 16), to porous carbon film (8, 9), to thin metallic absorbers (10,11,14,15), there is a clear trend to confine the absorbed energy in a thinner region for localized heating and more-efficient vapor generation, to minimize dissipated heat to the environment and bulk water. Impressive high-energy transfer efficiency has been achieved, but only for a limited amount of solution, with the assistance of both concentrators and thermal insulation.Efficient and effective solar desalination independent of water quantity under normal one-sun illumination without extra supporting systems will fund...

Solar steam generation is emerging as a promising technology, for its potential in harvesting solar energy for various applications such as desalination and sterilization. Recent studies have reported a variety of artificial structures that are designed and fabricated to improve energy conversion efficiencies by enhancing solar absorption, heat localization, water supply, and vapor transportation. Mushrooms, as a kind of living organism, are surprisingly found to be efficient solar steam-generation devices for the first time. Natural and carbonized mushrooms can achieve ≈62% and ≈78% conversion efficiencies under 1 sun illumination, respectively. It is found that this capability of high solar steam generation is attributed to the unique natural structure of mushroom, umbrella-shaped black pileus, porous context, and fibrous stipe with a small cross section. These features not only provide efficient light absorption, water supply, and vapor escape, but also suppress three components of heat losses at the same time. These findings not only reveal the hidden talent of mushrooms as low-cost materials for solar steam generation, but also provide inspiration for the future development of high-performance solar thermal conversion devices.

With recent progress in interfacial solar steam generation, direct solar desalination is considered a promising technology for providing a clean water solution through a cost effective and environmental‐friendly pathway. As a high and stable water production rate is the key to enable widespread applications, salt deposition becomes a critical issue that needs to be addressed. Herein, the authors demonstrate that a flexible Janus absorber fabricated by sequential electrospinning can enable stable and efficient solar desalination. Taking advantage of the unique structure of Janus, two functions of steam generation, solar absorption and water pumping, are decoupled into different layers, with an upper hydrophobic carbon black nanoparticles (CB) coating polymethylmethacrylate (PMMA) layer for light absorption, and a lower hydrophilic polyacrylonitrile (PAN) layer for pumping water. Therefore, salt can only be deposited in the hydrophilic PAN layer and quickly be dissolved because of continuous water pumping. Janus absorber demonstrates high efficiency (72%) and stable water output (1.3 kg m–2 h–1, over 16 days) under 1‐sun, not achieved in most previous absorbers. With a unique structure design achieved by scalable process, this flexible Janus absorber provides an efficient, stable and portable solar steam generator for direct solar desalination.

For the environmental energy-enhanced interfacial solar vapor generator, through elegant structural designs, there will be a net energy gain from the environment during the solar vapor generation, yielding an evaporation rate exceeding the theoretical value, assuming a 100% solar-to-vapor energy transfer efficiency.

Solar steam generation is emerging as promising solar-energy conversion technology for potential applications in desalination, sterilization and chemical purification. Despite the recent use of photon management and thermal insulation, achieving optimum solar steam efficiency requires simultaneous minimization of radiation, convection and conduction losses without compromising light absorption. Inspired by the natural transpiration process in plants, here we report a 3D artificial transpiration device with all three components of heat loss and angular dependence of light absorption minimized, which enables over 85% solar steam efficiency under one sun without external optical or thermal management. It is also demonstrated that this artificial transpiration device can provide a complementary path for waste-water treatment with a minimal carbon footprint, recycling valuable heavy metals and producing purified water directly from waste water contaminated with heavy metal ions.

In recent years, interfacial solar vapor generation has shown great potential in realizing desalination and wastewater treatment with high energy conversion efficiency. However, high evaporation rate cannot be maintained because of the seemingly unavoidable fouling or salt accumulation on the solar absorbers. The degradation accelerates as the solute concentration increases. Here, we demonstrate a water lily–inspired hierarchical structure that enables efficient evaporation (~80% solar-to-vapor efficiency) out of high-salinity brine [10 weight % (wt %)] and wastewater containing heavy metal ions (30 wt %). More notably, neither decrease in evaporation rate nor fouling on absorbers was observed during the entire evaporation process until water and solute were completely separated. With the capabilities of stable and high-rate evaporation out of high-salinity brine and the effective separation of solute from water, it is expected that this technology can have direct implications in various fields such as wastewater treatment, sea-salt production, and metal recycling.

The recent advancements in evaporating water using renewable energy provide one of the promising pathways for treating water with minimized carbon footprint. Pursuing a high evaporation rate of water has been the central focus of this field, as it is directly related to the throughput of evaporative water treatment. However, in conventional designs of evaporators, diffusion of vapor into the atmospheric environment has been the limiting step for evaporation. In this work, we demonstrate that a carbon foam with a three-dimensional interconnected porous structure enables sufficient diffusion of vapor with a convective flow and therefore realizes an evaporation rate as high as 10.9 kg m À2 h À1 and outdoor evaporation of 42.0 kg m À2 for continuous 13 h. With such a high evaporation rate achieved, it shows great promise toward a high-throughput, around-the-clock, and eco-friendly technology of evaporative wastewater disposal.

Earth, this solar device can generate clean water and electricity simultaneously, through storing and recycling the steam enthalpy derived from the interfacial solar steam-generation process. In addition, the integrated capability of thermal storage can enable electricity generation over an extended period after sunset. Combining conversion, storage, and utilization, this integrated solar energy device can provide the basic needs in various off-grid and/or resource-constrained areas.