Triple-Phase Interfacial Freestanding Fluffy Pine Needle Structures for Efficient Self-Powered Photoelectrocatalysis

Approximately 2 billion people still lack access to clean drinking water. Extensive efforts are underway to develop semiconductor photocatalysts for water disinfection and environmental remediation, but conventional liquid-solid diphase interfacial photocatalysts face challenges like low diffusion coefficients and limited solubility of dissolved oxygen. This study introduces freestanding copper oxide fluffy pine needle structures (CO-FPNs) with tunable water pollutants-gas-solid (WGS) triple-phase interfaces that enhance oxygen enrichment and reactive oxygen species (ROS) production. Three differently structured CO-FPNs-microdendrites, hierarchical dendrites, and nanowires-are designed. The hierarchical CO-FPN/WGS, predominantly in the Cassie-Wenzel coexistence state, showed a 1.81- to 1.91-fold higher reaction rate than the micro- and nanostructured CO-FPNs due to increased interfacial O₂ levels and high adsorption capability. Under illumination, the hierarchical CO-FPN/WGS achieved 99.999% sterilization by preventing pathogen adhesion and enhancing ROS generation. Additionally, a self-powered photoelectrocatalytic system is constructed using nickel-iron oxide-deposited bismuth vanadate (NiFeO/BiVO₄) with hierarchical CO-FPN/WGS, achieving 1.45 times higher than the hierarchical CO-FPN/WGS alone, due to superior oxidation kinetics of NiFeO/BiVO₄ and improved oxygen reduction via atmospheric oxygen from the hierarchical CO-FPN/WGS. This study demonstrates the first example of a triple-phase interfacial self-powered platform for efficient photoelectrocatalysis.