Sandwich-like reduced graphene oxide/yolk–shell-structured Fe@Fe3O4/carbonized paper as an efficient freestanding electrode for electrochemical synthesis of ammonia directly from H2O and nitrogen

Abstract

Ammonia is an important raw material in the fertilizer industry and a promising H-based fuel. However, its synthesis still largely relies on the conventional Haber–Bosch process, which is not only energy-consuming, but also environmentally damaging. Alternatively, the electrochemical synthesis of ammonia has drawn considerable interest. Herein, sandwich-like reduced graphene oxide/yolk–shell-structured Fe@Fe₃O₄/carbonized paper has been synthesized and employed as a freestanding electrode for nitrogen reduction reaction at room temperature and atmospheric pressure. The electrocatalytic measurements show that the as-obtained freestanding electrode exhibits high electrocatalytic activity (NH₃ formation rate of 1.3 × 10⁻¹⁰ mol cm⁻² s⁻¹), excellent selectivity (faradaic efficiency of 6.25%), and good stability, which are equivalent to (or even higher than) those of previously reported noble metal-based catalysts under comparable reaction conditions. The superior electrocatalytic performance of the rGO/Fe@Fe₃O₄/CP freestanding cathode for electrochemical synthesis of ammonia is mainly attributed to its unique sandwich-like nanoarchitecture with the middle yolk–shell-structured Fe@Fe₃O₄ nanoparticles and the synergistic effect between rGO and Fe@Fe₃O₄.