Single Iron-dimer Catalysts on MoS2 Nanosheet for Potential Nitrogen Activation

Electrocatalytic nitrogen reduction reaction(NRR) is a promising way to produce ammonia(NH) at ambient temperature and pressure. Herein, we have constructed single Fe dimer catalysts on a molybdenum disulfide monolayer for potential nitrogen activation. By employing ab initio molecular dynamics simulations, it is suggested that a dual iron-single atom site can be dynamically formed, which exhibits the similar Fe-S-Fe structure as the nitrogenase. We further identify an iron dimer with a sulfur vacancy as the active center for realistic nitrogen activation by the free energy calculations since the bridged sulfur is easy to be released in the form of HS during the reduction process. It is shown that N mainly adsorbs on the Fe dimer at the sulfur vacancies in the pattern of side-on configuration, and the nitrogen reduction reaction is proceeded by an enzymatic mechanism. Charge analyses further show that the Fe dimer mainly works as an electron reservoir while MoS substrate with one sulfur vacancy acts as an inert carrier to stabilize the Fe dimer. Overall, our work provides important insights into how N molecules were adsorbed and activated on Fe-doped MoS, and provides new ideas for the transformation of actual reaction sites during electrochemical reactions. [Figure not available: see fulltext.].