Carbon nanodots-based interfacial nanofluid for high-performance solar-driven water evaporation

Solar steam generation through volumetric heating using nanofluids is a promising approach for wastewater treatment and desalination. However, low evaporation rate and slow response time to the change in solar intensity seriously affect their cumulative evaporation performance in practice. Here, we propose an interfacial nanofluid structure for high-performance solar-driven water evaporation using carbon nanodot (CDs) nanofluid and airlaid paper. CDs nanofluid transferred down through the paper from a source water tank to form an interfacial evaporation structure and ensure continuous water supply for evaporation. The solar conversion heat was only localized on a small amount of nanofluid on the paper resulting in low heat loss to the bulk nanofluid and a fast response time of within 2 min to reach a steady evaporation rate. In addition, the flowing nanofluid on the paper can absorb environmental energy to achieve high-rate evaporation of 1.93 kg m⁻² h⁻¹ under one sun irradiation. This study provides an effective strategy to improve the performance of volumetric heating systems for solar wastewater treatment and desalination.