Robust mussel-inspired superhydrophobic sponge with eco-friendly photothermal effect for crude oil/seawater separation

Frequent oil spills have significant implications for the preservation of ecological balance. However, conventional superhydrophobic materials are limited to organic solvent separation, lacking the ability to undergo thermal conversion. In response to these challenges, photothermal materials have emerged as a promising, environmentally friendly, and cost-effective solution. These materials utilize solar energy as a constant power source to effectively reduce the viscosity of crude oil without the need for additional energy input. This work presents the self-assembly of titanium nitride/polydopamine (TiN/PDA) nanoparticles using hydrolytic methyltrimethoxysilane (MTMS) on the polyurethane (PU) sponge and subsequently dip-coats this sponge with polydimethylsiloxane (PDMS). The TiN nanoparticles act as a photothermal medium, while the PDA coating exhibits a photothermal synergistic effect on TiN nanoparticles. Additionally, the PDA coating demonstrates strong adhesion on the PU sponge through chemical bonding with MTMS, as confirmed by density functional theory (DFT). Furthermore, the superhydrophobic sponges process exceptional mechanical or chemical stability in harsh environments, thanks to the dual protective mechanisms provided by MTMS and PDMS. Particularly important, the excellent photothermal conversion efficiency of this material results in a maximum temperature of 99.4 °C being achieved within 3 min and a stable heating performance of over 99.0 °C across 10 cycles under a standard sunlight intensity. These superhydrophobic sponges can be effectively utilized for continuous vacuum-assisted separation of crude oil/seawater, enabling rapid adsorption and purification in oceanic environments.