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 (NO 3 RR) with sulfide oxidation reaction (SOR), which is implemented by developing CoRu/C and Co 9 S 8 nanosheets (NSs) as highly efficient electrocatalysts for the cathode and the anode, respectively. Both CoRu/C and Co 9 S 8 NSs exhibit significantly lower overpotential, faster kinetics, and high Faradaic efficiency (FE) for NO 3 RR 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 NH 3 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 NO 3 RR//OER. This work not only pioneers energy-efficient systems for pollutant degradation but also lays the groundwork for future advancements in chemical recovery.