Structural Reconstruction of Ce-MOF with Active Sites for Efficient Electrocatalytic N₂ Reduction

The electrochemical synthesis of ammonia from N₂ under mild conditions is a promising alternative to the energy-consuming Haber–Bosch process. Metal–organic frameworks (MOFs) are promising electrocatalysts for the N₂ reduction reaction, but most of them are active for the undesirable and competitive hydrogen evolution reaction. Herein, we developed a facile strategy to grow a Ce-MOF on copper mesh substrate. The Ce-MOF with a self-supporting structure could be directly used as an electrode for the N₂ reduction reaction, demonstrating highly efficient electrocatalytic performance with an NH₃ yield of 14.83 μg h^–1 cm^–2 and a Faradaic efficiency of 10.81% at −0.2 V versus a reversible hydrogen electrode. Structural characterizations of Ce-MOF after electrocatalysis revealed that Ce-MOF as precatalyst underwent structural reconstruction at negative potential, forming catalytically active CeO₂ with oxygen vacancies embedded in the amorphous Ce-MOF. In addition, the self-supporting structure formed by in situ growth of Ce-MOF on porous and conductive cooper mesh endowed the electrocatalyst with enhanced stability, conductivity, and mass transport. This work demonstrated the structural transformation of Ce-MOF during the electrocatalytic process and provided new insight for the rational design of MOF-based electrocatalysts.