Solar-hydrodynamic energy coupling enables round-the-clock algal inactivation in natural waters

Sustainable mitigation of harmful algal blooms in natural waters remains constrained by intermittent energy supply, quenching of reactive species (RS) in complex matrices, and limited recoverability of conventional nanocatalysts. Here, we report a piezo-photocatalytic strategy integrating ambient solar and hydrodynamic energy harvesting with floating catalyst deployment and selective RS regulation, enabling round-the-clock in situ algal control under realistic aquatic conditions. A Bi₄O₅I₂/Bi₂O₂S (6BIS) heterojunction couples light and mechanical energy harvesting, extending catalytic activity across illuminated and dark conditions when the corresponding energy input is available. In the dark, weak mechanical agitation yields ∼50% algal inactivation within 4.5 h via limited piezoelectric activation of peroxymonosulfate (PMS), increasing to 90% under ultrasonic stimulation. Under combined ultrasound and low-intensity visible light, complete algal inactivation is achieved within 2.5 h. Microcystin-LR (0.5 mg L^-1) is degraded within 5 min. Mechanistic investigations reveal that PMS adsorption at Bi sites selectively promotes superoxide radicals and singlet oxygen, mitigating quenching by humic substances. Field tests using a floating-supported catalyst achieved 55% algal inactivation within 8 h under natural sunlight and ambient hydrodynamic conditions. This work provides a strategy for improving the temporal continuity of environmental remediation by coupling ambient renewable energy harvesting with selective RS regulation.