Polypyrrole-Dopamine Nanofiber Light-Trapping Coating for Efficient Solar Vapor Generation

Heat-Localized and Salt-Resistant 3D Hierarchical Porous Ceramic Platform for Efficient Solar-Driven Interfacial Evaporation

Solar-driven interfacial evaporation (SDIE) is a highly promising approach to achieve sustainable desalination and tackle the global freshwater crisis. Despite advancements in this field, achieving balanced thermal localization and salt resistance remains a challenge. Herein, the study presents a 3D hierarchical porous ceramic platform for SDIE applications. The utilized alumina foam ceramics (AFCs) exhibit remarkable corrosion resistance and chemical stability, ensuring a prolonged operational lifespan in seawater or brines. The millimeter-scale air-filled pores in AFCs prevent thermal losses through conduction with bulk water, resulting in heat-localized interfaces. The hydrophilic nature of macroporous AFC skeletons facilitates rapid water replenishment on the evaporating surface for effective salt-resistant desalination. Benefiting from its self-radiation adsorption and side-assisted evaporation capabilities, the AFC-based evaporators exhibit high indoor evaporation rates of 2.99 and 3.54 kg m-2 h-1 under one-sided and three-sided illumination under 1.0 sun, respectively. The AFC-based evaporator maintains a high evaporation rate of ≈2.77 kg m-2 h-1 throughout the 21-day long-term test. Furthermore, it achieves a daily water productivity of ≈10.44 kg m-2 in outdoor operations. This work demonstrates the potential of 3D hierarchical porous ceramics in addressing the trade-off between heat localization and salt resistance, and contributes to the development of durable solar steam generators.

Self-healing and adhesive MXene-polypyrrole/silk fibroin/polyvinyl alcohol conductive hydrogels as wearable sensor

Conductive hydrogels become increasing attractive for flexible electronic devices and biosensors. However, challenges still remain in fabrication of flexible hydrogels with high electrical conductivity, self-healing capability and adhesion property. Herein, a conductive hydrogel (PSDM) was prepared by solution-gel method using MXene and dopamine modified polypyrrole as conductive enhanced materials, polyvinyl alcohol and silk fibroin as gel networks, and borax as cross-linking agent. Notably, the PSDM hydrogels not only showed high permeability (13.82 mg∙cm-2∙h-1), excellent stretch ability (1235 %), high electrical conductivity (11.3 S/m) and long-term stability, but also exhibited high adhesion performance and self-healing properties. PSDM hydrogels displayed outstanding sensing performance and durability for monitoring human activities including writing, finger bending and wrist bending. The PSDM hydrogel was made into wearable flexible electrodes and realized accurate, sensitive and reliable detection of human electromyographic and electrocardiographic signals. The sensor was also applied in human-computer interaction by collecting electromyography signals of different gestures for machine learning and gesture recognition. According to 480 groups of data collected, the recognition accuracy of gestures by the electrodes was close to 100 %, indicating that the PSDM hydrogel electrodes possessed excellent sensing performance for high precision data acquisition and human-computer interaction interface.

Enabling Further Organic Electrolyte Infiltration of Cellulose-Based Separators via Defect-Rich Polypyrrole Modification for High Sodium Ion Transport in Sodium Metal Batteries

Sodium metal batteries (SMBs) have high-density and cost-effective characteristics as one of the energy storage systems, but uncontrollable dendrite growth and poor rate performance still hinder their practical applications. Herein, a nitrogen-rich modified cellulose separator with released abundant ion transport tunnels in organic electrolyte was synthesized by in situ polymerization of polypyrrole, which is based on the high permeability of cellulose in aqueous solution and the interfacial interaction between cellulose and polypyrrole. Meanwhile, the introduction of abundant structural defects such as branch chains, oxygen-containing functional groups, and imine-like structure to disrupt polypyrrole conjugation enables the utilization of conductive polymers in composite separator applications. With the electrolyte affinity surface on, the modified separator exhibits reinforced electrolyte uptake (254%) and extended electrolyte wettability, thereby leading to accelerated ionic conductivity (2.77 mS cm-1) and homogeneous sodium deposition by facilitating the establishment of additional pathways for ion transport. Benefiting from nitrogen-rich groups, the polypyrrole-modified separator demonstrates selective Na+ transport by the data of improved Na+ transference number (0.62). Owing to the above advantages, the battery assembled with the modified separators exhibits outstanding rate performance and prominent capacity retention two times that of the pristine cellulose separator at a high current density under the condition of fluorine-free electrolyte.

Sustainable Seawater Desalination and Energy Management: Mechanisms, Strategies, and the Way Forward

Solar-driven desalination systems have been recognized as an effective technology to address the water crisis. Recently, evaporators prepared based on advanced manufacturing technologies have emerged as a promising tool in enhancing ocean energy utilization. In this review, we discussed the thermal conversion, energy flow, salt deposition mechanisms, and design strategies for solar-driven desalination systems, and explored how to improve the desalination performance and energy use efficiency of the systems through advanced manufacturing technologies. In future perspectives, we determined the feasibility of coupling solar-driven solar desalination systems with multi-stage energy utilization systems and emerging artificial intelligence technologies, for which conclusions are given and new directions for future desalination system development are envisioned. Finally, exciting opportunities and challenges in the face of basic research and practical implementation are discussed, providing promising solutions and blueprints for green and novel desalination technologies while achieving sustainable development.

Polydopamine/Fe3O4 modified wood-based evaporator for efficient and continuous water purification

Solar interfacial evaporation is a highly promising technology for seawater desalination and wastewater treatment, while the simple preparation processes and efficient production of clean water based on biomass interfacial evaporators still need further exploration and development. Here, we reported a wood-based evaporator (PFDW) loaded with Fe3O4 and polydopamine (PDA) after simple immersion treatment at room temperature for efficient and continuous water purification. The synergistic photothermal effect of PDA coating and Fe3O4 particles enables the evaporator to achieve high photothermal conversion efficiency in the longer wavelength range, while combined with the rapid water transport capacity endowed by the vertically aligned microporous structure of natural wood, it achieved an evaporation rate of 1.70 kg m-2h-1 and an energy efficiency of 98.0% under 1 kW m-2 irradiation. In addition, the prepared PFDW exhibited sustainable desalination stability and excellent removal efficiency for different water sources including organic dye wastewater, heavy metal effluent, oil-water emulsion and river water. This work provides a new avenue for efficient salt-tolerant portable evaporators.

Conjugated photothermal materials and structure design for solar steam generation

With the development of solar steam generation (SSG) for clean water production, conjugated photothermal materials (PTMs) have attracted significant interest because of their advantages over metallic and inorganic PTMs in terms of high light absorption, designable molecular structures, flexible morphology, and solution processability. We review here the recent progress in solar steam generation devices based on conjugated organic materials. Conjugated organic materials are processed into fibers, membranes, and porous structures. Therefore, nanostructure design based on the concept of nanoarchitectonics is crucial to achieve high SSG efficiency. We discuss the considerations for designing SSG absorbers and describe commonly used conjugated organic materials and structural designs.

Double-Sided Suspending Evaporator with Top Water Supply for Concurrent Solar Evaporation and Salt Harvesting

Solar evaporation of seawater is promising to mitigate the fresh water scarcity problem in a green and sustainable way. However, salt accumulation on the photothermal material prevents the system continuous operation, and the water supply driven by capillary force severely limits the scale-up of the evaporators. Here, we demonstrate a double-sided suspending evaporator with top water supply and a surface water distributor for high-efficient concurrent solar evaporation and salt harvesting for large area applications. Both sides of the evaporator can evaporate water with automatic salt harvesting from the edge concurrently. Top water supply gets away from the limitation of capillary force for a larger area application and completely cuts off the heat leak to the bulk water below for higher efficiency. The energy conversion efficiency reaches 95.7% at 1.40 kg·m^-2·h^-1 with deionized water under 1 sun with a remarkable low surface average temperature (28.2 °C). Based on the simulation and experiment, a novel radial arterial water distribution system is developed to efficiently distribute water on a larger evaporation surface. The water distribution system alters the water transport path in the evaporation surface, leading to salt accumulation on the surface body, where salt is unable to be harvested by gravity automatically. This problem is further resolved by cutting out the salt accumulation area (16.4%) on the surface to create a floriform evaporator, which forcedly exposes the salt at the edge for harvesting. Up to70 h continuous solar evaporation from salt water at a rate of 1.04 kg·m^-2·h^-1 with concurrent salt collection on this floriform evaporator is achieved. This work resolves water supply and salt accumulation problems in scaling up the solar evaporators and advances the structural design of evaporators for high-efficient large area applications.

Simple Design of a Porous Solar Evaporator for Salt-Free Desalination and Rapid Evaporation

Solar-driven interfacial evaporation is considered to be one of the promising and efficient ways of producing clean water in recent years. However, it remains a challenge to develop solar evaporation devices with high solar evaporation rates and salt-free blocking properties. Here, a porous solar evaporator with directed water transport and salt-free desalination through excellent photothermal conversion and purposefully guided migration of the salt solution was developed. The designed porous photothermal sponge with the synergistic effect of MXene and polypyrrole can achieve evaporation rates of 1.47 and 2.27 kg m^-2 h^-1, respectively, in the capillary model and siphon model water-transporting solar evaporation devices. More interestingly, the designed zigzag-shaped device with an evaporation rate of 2.45 kg m^-2 h^-1 was achieved. In addition, the evaporator can operate stably under 9 h in the siphon model solar evaporation device and achieves the effect of salt-free desalination. The above design provides a good strategy for solar-powered desalination applications.