Structural Reconstruction of Ce-MOF with Active Sites for Efficient Electrocatalytic N-2 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 N-2 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 N-2 reduction reaction, demonstrating highly efficient electrocatalytic performance with an NH3 yield of 14.83 mu g 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 CeMOF. 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.