Atomic Molybdenum for Synthesis of Ammonia with 50% Faradic Efficiency.

Abstract

The electrochemical dinitrogen (N2 ) reduction reaction (NRR) under ambient conditions has gained significant interest as an environmentally friendly alternative to the traditional Haber-Bosch process for the synthesis of ammonia (NH3 ). However, up to now, most of the reported NRR electrocatalysts with satisfactory catalytic activities have been hindered by the large overpotential in N2 activation. The preparation of highly efficient Mo-based NRR electrocatalyst in acidic electrolytes under ambient conditions is demonstrated here, consisting of stabilized single Mo atoms anchored on holey nitrogen-doped graphene synthesized through a convenient potassium-salt-assisted activation method. At -0.05V versus a reversible hydrogen electrode (RHE), an electrode consisting of the resultant electrocatalyst immobilized on carbon fiber paper can attain an exceptional Faradaic efficiency of 50.2% and a NH3 yield rate of 3.6µg h-1 mgcat-1 with low overpotentials. Density functional theory calculations further unveil that compared to the original graphene without holes, the edge coordinated Mo atoms and the existence of vacancies on holey graphene lower the overpotential of N2 reduction, thereby promoting the NRR catalytic activity. This work could provide new guidelines for future designs in single-atom catalysis that would be beneficial to ambient N2 fixation, and replacement of classical synthesis processes that are very energy-intensive.