A self-powered aluminum-nitrate battery coupled with chemical reduction for selective nitrate-to-N2 conversion in natural water

With its diverse sources and strong mobility, nitrate has become one of the most common contaminants in natural water bodies worldwide, posing an increasingly serious threat to ecosystems and human health. The wide spatial distribution of nitrate pollution makes traditional centralized treatment techniques (e.g., biological denitrification and reverse osmosis) impractical. Here, we address this challenge by developing an easily deployable decentralized system coupling a self-powered aluminum-nitrate (Al-NO 3 − ) battery with chemical reduction. The metal Al anode undergoes controlled oxidation, and the spontaneously generated electrons drive nitrate reduction to nitrite at the surface-reconstructed silver mesh (SRSM) cathode. The driving force originates from the potential difference between electrodes, requiring no external power supply. A proton exchange membrane physically separates the chambers, completely avoiding aluminum ion leakage and secondary pollution, while dissolved Al precipitates into recyclable aluminum hydroxide. Sodium ascorbate addition suppresses hydrogen evolution reaction at the Al surface, increasing utilization efficiency from 3.54% to 33.69%. Subsequently, the nitrite is quantitatively converted to N 2 by reduction with sulfamic acid. The system achieves highly selective conversion of nitrate to benign N 2 . Notably, the system operates efficiently in real water bodies (tap, lake, and groundwater) without requiring supporting electrolyte addition, achieving up to 94% nitrate removal and 99% N 2 selectivity. Long-term testing demonstrates that removal rate remains above 70% and N 2 selectivity is near perfect after 20 operating cycles. This off-grid, green technology provides a practical decentralized remediation solution for widespread nitrate pollution.