<p>The bioaccumulation of hepatotoxic Microcystin-RR (MC-RR) in aquatic products poses a severe threat to human health via the food chain, underscoring the urgent need for sensitive detection methods. Herein, a self-powered electrochemical aptasensor was developed for on-site MC-RR monitoring based on ZIF-67/g-C₃N₄ heterojunctions. By coupling hydrovoltaic and photoelectric effects, the engineered built-in electric field significantly enhanced charge separation and water evaporation, amplifying the electrical signal by 11-fold under illumination. The aptamer-functionalized platform enabled specific MC-RR detection via modulating the interfacial charge transfer, achieving a wide linear range from 1 × 10^− 14 M to 1 × 10^− 10 M and an ultra-low detection limit of 2.36 × 10^− 15 M. Furthermore, the sensor demonstrated excellent selectivity against interfering substances and was successfully applied to the analysis of aquaculture water and crucian carp samples. This work presents a sustainable, high-performance self-powered sensing platform for early cyanotoxin screening to safeguard aquatic food safety. Its advantages of simple operation and high sensitivity make it a promising tool for on-site food safety monitoring.</p> Graphical Abstract <p></p>