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 (NH₃) synthesis. However, electrostatic repulsion between nitrate (NO₃⁻) and the cathode impedes NO₃⁻ 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 NO₃⁻ and the cathode but also enhances the selectivity of NH₃ by preventing the formation of adsorbed H⁺ on the electrode. Remarkably, the addition of CsOH enables an NH₃ 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 NO₃⁻. Furthermore, the Zn-NO₃ 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 NO₃⁻ reduction but also successfully demonstrates a Zn-NO₃ battery capable of simultaneous high-efficiency NH₃ synthesis and electric power generation.