Electrochemical ammonia synthesis catalyzed with a CoFe layered double hydroxide – A new initiative in clean fuel synthesis

Electrochemical ammonia synthesis is regarded as a green, clean, and sustainable technology alternative to the Haber-Bosch process to reduce fossil fuel consumption and greenhouse gas emission. In this research, an earth-abundant CoFe layered double hydroxide was prepared with a simple one-step hydrothermal method and was employed as a promising catalyst for electrochemical ammonia synthesis. The CoFe double hydroxide exhibited excellent catalytic activity with a high generation rate of 1.1 × 10⁻⁹ mol s⁻¹ cm⁻² in a single-chamber cell, and a high Faradaic efficiency of 14.18% was obtained when the concentration of protons and electrons was limited in a double-chamber cell. The outstanding catalytic performance of CoFe layered double hydroxide was attributed to the abundant N₂ adsorption sites provided by the binder-free three-dimensional nano-structure and the synergy between the Co and Fe atoms in the layer. A microkinetic model of electrochemical ammonia synthesis catalyzed with CoFe layered double hydroxide was proposed, which was consistent with the experimental results. A possible ammonia synthesis mechanism was proposed based on the experiments and theoretical calculations.