Design of a facile self-floating bio-based Janus evaporators for efficient and stable solar desalination

The utilization of solar-driven photothermal evaporators for desalination offers a highly attractive solution to address the current global freshwater shortage, necessitating the development of scalable and efficient interfacial solar evaporators. In this study, we successfully fabricated a cost-effective Janus evaporator using bio-based chitosan (CS) and epoxidized natural rubber (ENR) latex (CS@ENR) aerogel by controlling single-sided deposition of polypyrrole (Ppy) through in-situ polymerization, followed by subsequent modification with hydrophobic polydimethylsiloxane (PDMS). The PP-CS@ENR (PDMS/Ppy-CS@ENR) aerogel presented high light absorption (95 %) and excellent photothermal conversion capacity (up to 67.7 °C) in the full solar spectrum. The water evaporation rate of the Janus PP-CS@ENR under one sun illumination was 2.16 kg·m −2 ·h −1 , with a superior photothermal conversion efficiency of 91 %. Moreover, the evaporator exhibits exceptional recycling capability and demonstrates a consistent water evaporation rate ≥ 2.0 kg·m −2 ·h −1 after 14 days of continuous evaporation cycles. The daily production of desalinated water under outdoor solar condition is 14.8 kg per square meter (over an 8-hour period), which adequately satisfies the drinking requirements of seven adult individuals. Therefore, these advantage properties of the PP-CS@ENR biomass-based Janus evaporator enable its versatile applications in solar-driven interfacial evaporation systems.