Trench-Like Piezoelectric Coating for Efficient Removal of Pollutants under All-Weather Conditions

Photocatalytic hydrophobic self-cleaning coatings are a promising means for protecting buildings from environmental damages; however, it still remains a big challenge to develop redox-active catalysts that green-efficiently decompose persistent organic pollutants, directly harnessing natural energy such as the kinetic energy of rainfall and solar energy without the need for high power consumption, while maintaining robust performance under all-weather conditions. Herein, we constructed a functional composite coating with piezo-photocatalytic and hydrophobic self-cleaning properties. Under simulated all-weather conditions, it exhibited excellent pollutant removal efficiency, achieving approximately 94.23% for RhB in 80 min and 94.20% and 90.56% for TC and OTC, respectively, within 5 h. Also, it demonstrated that under flow impact alone, the stress energy variations (maximum value of 3.968 × 10^-5 per droplet), resulting from different heights and incident angles, significantly affected pollutant removal efficiency. The stress induced by water flow activated the piezoelectric response. The maximum droplet spreading radius reached up to 3.5 times the initial, enlarging the solid-liquid contact area by roughly 12.25 times, which greatly promoted mass transfer and oxygen access and amplified reactive oxygen species (ROS) generation as 22.55 μM ^•OH and 23.04 μM ^•O₂^- under water-flow conditions. In addition, it also exhibited outstanding mechanical durability and strong antibacterial activity of 95.79%. Atomic force microscopy (AFM) revealed a high fitted modulus of 56.7 GPa and an ultralow adhesion force of 91.1 nN, corroborating the coating's stiffness and hydrophobic self-cleaning capability. These properties stemmed from the microrough, channel-like architecture of the piezo-photocatalytic hydrophobic coating (PHSC) framework, which enhances contact stiffness and reduces fouling adhesion. Overall, this work presented a scalable and energy-efficient strategy for maintaining outdoor surface cleanliness and hygiene by passively utilizing ambient energy at the solid-liquid-gas interface.