Green steam from sunlight: interfacial evaporation enabling low-carbon solutions

Interfacial solar evaporation is an emerging technology that enables efficient water evaporation by converting solar energy into localized heat at the water-air interface. This technology utilizes solar-driven interface evaporators deployed on the water surface, requiring no external energy input while achieving high-efficiency steam generation. The core of this process lies in the use of highly efficient photothermal conversion materials that effectively capture solar radiation and localize the absorbed energy, directly transforming sunlight into heat to drive water evaporation. Because this method relies solely on solar energy, the generated steam is considered “green steam”, as the entire process operates with near-zero carbon emissions. This sustainable approach holds great potential in seawater desalination, wastewater treatment, and steam-driven power generation. Particularly in remote and resource-scarce regions, interfacial solar evaporation offers a sustainable and cost-effective solution for resource acquisition, providing new hope for addressing global water shortages.Green steam generated through interfacial solar evaporation has a broad range of applications. One of the most significant uses is in clean water production, where it can efficiently extract fresh water from various sources, including seawater, brackish water, and industrial wastewater. This makes it an ideal solution for household water supply, agricultural irrigation, and emergency drinking water production in disaster-stricken areas. In addition, interfacial solar evaporation is highly effective in wastewater treatment. It enables the purification of municipal sewage and industrial effluents from sectors such as textile manufacturing, thermal power plants, and the pharmaceutical industry, achieving zero liquid discharge by fully separating water from contaminants. Beyond water purification, this technology has demonstrated excellent performance in sterilization and disinfection, making it useful in healthcare, sanitation, and food safety applications. Furthermore, green steam generation through interfacial solar evaporation can be integrated with renewable energy technologies for electricity production, increasing its practicality and expanding its impact in sustainable energy systems.Over the past decade, significant advancements have been made in interfacial solar evaporation, pushing the technology close to its thermodynamic efficiency limit. Under concentrated solar illumination, freshwater production rates have exceeded 80 L m–2 h–1, with stable operation extending beyond 600 hours. These improvements have positioned interfacial solar evaporation as a highly promising clean energy solution. However, despite these impressive laboratory achievements, several critical challenges remain for large-scale deployment. One major obstacle is maintaining high efficiency and stability in real-world conditions, as external factors such as contamination, environmental fluctuations, and long-term durability must be considered. Additionally, reducing the cost of photothermal materials and evaporation devices is crucial to making this technology economically viable for widespread adoption. Addressing these challenges requires further research and innovation in material design, system engineering, and large-scale implementation strategies.This review systematically summarizes the latest advancements in interfacial photothermal green steam across energy, resources, agriculture, environment, and health sectors. It thoroughly explores innovative strategies in material design, device construction, and system integration, while evaluating production potential, application feasibility, and developmental challenges. Finally, it envisions full-spectrum solar utilization and multi-product co-production based on green steam, aiming to enhance comprehensive solar energy efficiency and pave new pathways for China’s green, low-carbon industrial development and circular economy system.