Facile fabrication of superhydrophobic and photocatalytic ZrO<sub>2</sub>@TiO<sub>2</sub>@polydimethylsiloxane coating for efficient self-cleaning and oil-water separation.

Abstract

Since most superamphiphobic coatings contain fluorinated materials, finding eco-friendly alternatives is essential. In recent years, researchers have focused on integrating eco-friendly photocatalytic materials into superhydrophobic coatings to degrade organic pollutants effectively. We successfully designed a porous ZrO₂@TiO₂ (porous ZT) photocatalyst using a combination of the solvothermal, sol-gel, and calcination methods. Porous ZT was modified with polydimethylsiloxane (PDMS) to create a kind of ZrO₂@TiO₂@PDMS (porous ZTP) suspension. The ZTP suspension was then sprayed onto various substrates and heated at 400 °C for 2 min to produce a porous ZrO₂@TiO₂@PDMS (porous H-ZTP) composite coating. The porous H-ZTP coating demonstrates extremely low surface energy (2.37 mN/m), allowing it to prevent contamination from various liquids encountered in daily life while exhibiting outstanding superhydrophobic properties (WCA > 160°, SA < 2°). Additionally, it can decompose organic substance (RhB) under light irradiation, showcasing effective physical and chemical self-cleaning abilities. After exposure to ultraviolet light, the coating can decompose oleic acid and restore its initial superhydrophobic state. Further investigation into the mechanism of photocatalytic degradation reveals that the unique heterojunction structure of the porous ZT significantly enhances its photocatalytic activity. The porous H-ZTP applied onto stainless steel mesh shows excellent flux (40,000 L·h^-1m^-2) and efficiency (99 %) for oil-water separation. This research is significant for developing and applying self-cleaning coatings that combine physical superhydrophobic and chemical photocatalytic properties.