Cobalt-Modulated Molybdenum-Dinitrogen Interaction in MoS₂ for Catalyzing Ammonia Synthesis

Dinitrogen conversion to ammonia via electrochemical reduction with over 10% Faradaic efficiency is demonstrated in this work. Co-doped MoS_2-x polycrystalline nanosheets with S vacancies as the catalysts are loaded onto carbon cloth by hydrothermal growth from Mo, Co, and S precursors. A sulfur vacancy on the MoS_2-x basal plane mimicking the natural Mo-nitrogenase active site is modified by Co doping and exhibits superior dinitrogen-to-ammonia conversion activity. Density-functional simulation reveals that the free energy barrier, which can be compensated by applied overpotential, is reduced from 1.62 to 0.59 eV after Co doping. Meanwhile, dinitrogen tends to be chemically adsorbed to defective MoS_2-x, which effectively activates the dinitrogen molecule for the dissociation of the N≡N triple bond. This process is further accelerated by Co doping, resulting from the modulation of Mo-N bonding configuration. © 2019 American Chemical Society.