Energy-Saving Electrolyzer for Cost-Effective Co-Recovery of Ammonia and Sulfur

Nitrate and sulfide, as typical pollutants from industrialization and agriculture, remain challenging to cleanly transform for eco-friendly development. However, the rational integration of their coupled recycling and energy-saving conversion has received scant attention. Herein, we present a thermodynamically optimized electrolytic cell integrating nitrate reduction reaction (NO3RR) with sulfide oxidation reaction (SOR), which is implemented by developing CoRu/C and Co9S8 nanosheets (NSs) as highly efficient electrocatalysts for the cathode and the anode, respectively. Both CoRu/C and Co9S8 NSs exhibit significantly lower overpotential, faster kinetics, and high Faradaic efficiency (FE) for NO3RR and SOR. The integrated nitrate–sulfide electrolyzer achieves 100 mA cm–2 at an ultralow potential of 0.56 V and demonstrates robust stability at 200 mA cm–2 over an extensive 240 h operation. The scaled-up system delivers ampere-level currents, enabling large-scale NH3 and S production. It reduces 60% energy consumption and generates a net profit of $1.67 per kilogram of ammonia from the dual-recovery of ammonia and sulfur, yielding a notable 7.60-fold enhancement over the NO3RR//OER. This work not only pioneers energy-efficient systems for pollutant degradation but also lays the groundwork for future advancements in chemical recovery.