Ag/Ag-Zn IMC-Enhanced Photocatalytic and Antibacterial Properties of Cauliflower-like ZnO Nano-Composite Coatings Prepared by Plasma Spraying-Chemical Vapor Deposition

Photocatalytic coatings enable efficient degradation of environmental pollutants and inactivation of waterborne pathogens, while offering superior reusability and eliminating secondary pollution risks. This study reports a porous ZnO/Ag/Zn/Ag-Zn intermetallic compound (IMC) composite coating fabricated by plasma spraying–chemical vapour deposition (PS-CVD) using a homemade Zn@(Ag/ZnO) core-shell powder. The unique core-shell structure promotes explosive boiling of the Zn core and subsequent vapour-phase deposition, yielding a dendritic coating architecture composed of nanoparticles (40–90 nm) with abundant heterojunction interfaces. The coating exhibits excellent photocatalytic and antibacterial performance. This performance is attributed to the localized surface plasmon resonance (LSPR) effect of the Ag and Ag-Zn IMC nanoparticles. This effect enhances visible light absorption, narrows the ZnO band gap to 2.74 eV, and promotes the generation of reactive oxygen species (ROS). Under simulated sunlight, its photodegradation rate constants are 1.5–3 times higher than those of pure nano-ZnO. Furthermore, the antibacterial efficiencies exceed 98.0% against S. aureus and 97.5% against E. coli. under LED illumination, and reach 94% against both bacteria even in the dark, via the release of Ag⁺/Zn²⁺ ions. Consequently, the PS-CVD method offers a scalable route for fabricating high-performance photocatalytic and antibacterial coatings characterized by fine grains and a high specific surface area.