Unveiling multi-element synergy in polymetallic oxides for efficient nitrate reduction to ammonia

Electrocatalytic nitrate reduction reaction is considered as a promising and sustainable method for ammonia synthesis. However, the selectivity and yield rate of ammonia are limited by the competitive hydrogen evolution reaction and the complex eight-electron transfer process. Herein, we developed a (FeCoNiCu)Ox/CeO₂ polymetallic oxide electrocatalyst for effective nitrate reduction to ammonia. The synergistic effects among the multiple elements in the electrocatalyst were clearly elucidated by comprehensive experiments. Specifically, Cu acted as the active site for reducing nitrate to nitrite, and Co facilitated the subsequent reduction of nitrite to ammonia, while Fe and Ni promoted water dissociation to provide protons. Furthermore, the incorporation of CeO₂ increased the active surface area of (FeCoNiCu)Ox, resulting in an improved ammonia yield rate to meet industrial demands. Consequently, the (FeCoNiCu)Ox/CeO₂ electrocatalyst achieved an ammonia current density of 382 mA cm⁻² and a high ammonia yield rate of 30.3 mg h⁻¹ cm⁻² with a long-term stability. This work offers valuable insights for the future design of highly efficient multi-element electrocatalysts.