Trace CsOH Additive Promotes the Reduction of Nitrate to Ammonia

The electrocatalytic nitrate reduction reaction represents a promising technology for wastewater treatment while enabling electrochemical ammonia (NH 3 ) synthesis. However, electrostatic repulsion between nitrate (NO 3 – ) and the cathode impedes NO 3 – diffusion into the electric double layer, thereby hindering the reaction. Herein, the diffusion limitation is mitigated by introducing a trace CsOH additive to the electrolyte, and the underlying mechanism is systematically elucidated. CsOH not only weakens the static repulsion between NO 3 – and the cathode but also enhances the selectivity of NH 3 by preventing the formation of adsorbed H + on the electrode. Remarkably, the addition of CsOH enables an NH 3 production rate of 456.2 μmol cm –2 h –1 at 150 mA cm –2 with a faradaic efficiency of 65.2% in 20 mM NO 3 – . Furthermore, the Zn–NO 3 battery with a CsOH additive achieves a peak power density of 30.16 mW cm –2 . This work not only provides fundamental insights of additive-enhanced NO 3 – reduction but also successfully demonstrates a Zn–NO 3 battery capable of simultaneous high-efficiency NH 3 synthesis and electric power generation.