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 (NO3RR) technology provides an energy-efficient alternative to traditional ammonia (NH3) synthesis while promoting environmental sustainability. Herein, we synthesized hierarchical CuCo2O4 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, CuCo2O4 NDs achieve a high Faradaic efficiency (97.86%) and an impressive NH3 yield (34.23 mg h–1 mgcat–1) at −0.3 V for NO3RR, accompanied by excellent stability. These properties arise from the synergistic effect of Cu–Co pairs and the two-dimensional architecture. When applied in a CuCo2O4 NDs||CuCo2O4 NDs electrolyzer, the HzOR-assisted NO3RR operates at 0.997 V (10 mA cm–2), which is 573 mV lower than the conventional NO3RR system with oxygen evolution. This work presents a low-voltage NH3 synthesis strategy coupled with nitrogen pollutant mitigation.