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.