Ceramic Whiskers Grafted with Liquid-Like Surface for Scalable Underwater Methane Collection

Efficient underwater methane capture is essential for mitigating greenhouse gas emissions. Although a few studies have reported using superhydrophobic surfaces to capture methane bubbles underwater, achieving long-term, fast, and scalable underwater methane bubble collection still faces significant challenges. Here, a rigid plate-like porous skeleton made of <i>in situ</i>-grown mullite whiskers is presented. The surface silanol groups of the whiskers covalently bond with PDMS chains at low temperature, forming a liquid-like surface. Unlike conventional liquid-like surfaces formed on smooth macroscopic substrates, the liquid-like layer here forms on the surfaces of the fine whiskers inside the porous skeleton, i.e., on the internal walls of the pores. Transmission electron microscopy (TEM) was employed to directly measure the layer thickness (2.4-6.1 nm) on the whisker surface. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) was used to analyze the distribution of the layer on individual whiskers. The skeletons show excellent low contact angle hysteresis (2°) and long-term underwater superhydrophobic stability (up to 30 days). They were assembled in series, parallel, or hybrid configurations to enable scalable and continuous methane bubble collection. When a 1 mm-thick plate was submerged at a depth of 85 cm, a collection rate of approximately 4.38 mL·min^-1·cm^-2 was achieved. Continuous underwater gas collection was monitored for 48 h by video. This combination of a ceramic whisker skeleton and a liquid-like surface offers a promising strategy for large-scale methane bubble collection with long-term stability and high collection rates.