Energy-Efficient Ammonia Production via Coupled Hydrazine Hydrate Oxidation Using CuCo₂O₄ Nanodendrites with Ultrathin Nanosheet Subunits

The hydrazine oxidation reaction (HzOR)-assisted nitrate reduction reaction (NO 3 RR) technology provides an energy-efficient alternative to traditional ammonia (NH 3 ) synthesis while promoting environmental sustainability. Herein, we synthesized hierarchical CuCo 2 O 4 nanodendrites (NDs) composed of ultrathin nanosheet subunits with a spinel structure via a simple coprecipitation method followed by annealing. This spinel framework features well-defined Cu–Co pairs. In an alkaline solution, CuCo 2 O 4 NDs achieve a high Faradaic efficiency (97.86%) and an impressive NH 3 yield (34.23 mg h –1 mg cat –1 ) at −0.3 V for NO 3 RR, accompanied by excellent stability. These properties arise from the synergistic effect of Cu–Co pairs and the two-dimensional architecture. When applied in a CuCo 2 O 4 NDs||CuCo 2 O 4 NDs electrolyzer, the HzOR-assisted NO 3 RR operates at 0.997 V (10 mA cm –2 ), which is 573 mV lower than the conventional NO 3 RR system with oxygen evolution. This work presents a low-voltage NH 3 synthesis strategy coupled with nitrogen pollutant mitigation.