Solar evaporation has attracted great interest in water collection, gaining considerable attention recently. While many efforts have been made to enhance solar thermal conversion performance from materials design aspects, little attention has been given to the fundamental solar thermal gradient concept, which significantly affects local heating during evaporation. In this work, the polymer sponge evaporator was designed to control the solar thermal gradient by adding copper–carbon core–shell (Cu@C) nanoparticles with similar solar absorptance to understand the effect of solar thermal gradient or local heating on evaporation performance. The optimized solar evaporation can be 2.0 kg·m⁻²·h⁻¹ under 1000 W·m⁻² (one sun) with a Cu@C mass fraction of 0.5 wt.%, which was higher than that observed in cases with either higher or smaller Cu@C mass fraction. A too-small or large Cu@C mass fraction would enhance heat loss from the bottom or top parts, which was also confirmed by simulation results. Further outdoor water yield experiment showed that the optimized Cu@C mass fraction of 0.5 wt.% achieved the highest water collection (6.67 kg·m⁻²·d⁻¹) compared with the other cases, such as 5.92 kg·m⁻²·d⁻¹ for 0.1 wt.%, 5.29 kg·m⁻²·d⁻¹ for 1 wt.%. These results highlighted the impact of local heating on evaporation performance under the solar thermal gradient during the solar evaporation process.

As global energy demand continues to rise and climate change accelerates, the need for sustainable and energy-efficient cooling solutions has reached a critical level. Conventional air conditioning systems heavily rely on energy-intensive mechanical cooling, which significantly contributes to both electricity demand and greenhouse gas emissions. Passive cooling strategies, particularly radiative cooling (RC) and evaporative cooling (EC), present an alternative approach by harnessing natural processes for temperature regulation. While standalone RC can be affected by weather conditions and EC relies on water availability, Radiative-coupled EC (REC) offers a versatile and sustainable cooling solution suitable for various applications. Here we summarize an overview of the theoretical foundations and mathematical models of REC, encompassing REC by bulk water (REC-BW), REC by perspiration (REC-P), and REC by sorbed water (REC-SW). Moreover, we explore a range of applications, spanning from industrial processes to personal thermal management, and examine the advantages and challenges associated with each REC approach. The significance of REC lies in its potential to revolutionize cooling technology, reduce energy consumption, and minimize the environmental impact. REC-BW can conserve water resources in industrial cooling processes, while REC-P offers innovative solutions for wearable electronics and textiles. REC-SW’s adaptability makes it suitable for food preservation and future potable cooling devices. By addressing the challenges posed by REC, including water consumption, textile design, and optimization of bilayer structures, we can unlock the transformative potential of REC and contribute to sustainable cooling technologies in a warming world.