Revealing the Origin of Nitrogen Electroreduction Activity of Molybdenum Disulfide Supported Iron Atoms

Despite encouraging progress in electrocatalytic nitrogen reduction reaction (NRR) catalyst development, efficient NRR has proven extremely challenging to achieve in practice, underscoring the fact that N-2 is a highly stable, non-polar molecule. Hence, discovering electrocatalysts with considerable yields for NRR is highly desired. In this work, combining the state-of-the-art ab initio molecular dynamics and the computational standard hydrogen electrode method, we studied the thermodynamics and kinetics of NRR on Fe-x@MoS2 (x = 1-3) electrocatalysts under an applied electrochemical environment. NH2-NH2 was determined to be an important intermediate, and its N-N bond breaking was proposed as the rate-determining step. On Fe-1@MoS2, we demonstrated that the NRR activity of Fe-1@MoS2 can be attributed to the electric field effect, which triggers the dynamical orientation of NH2-NH2 from side-on adsorption mode to end-on one. The induced interaction between the dipole moment of the titled N-N bond with the local electric field facilitates the N-N bond cleavage. On the contrary, such an electric field effect on Fe-2@MoS2 and Fe-3@MoS2 is minor. Two Fe sites synergistically interacting with NH2-NH2 leads to more efficient N-N bond activation than Fe-1@MoS2. This work not only illuminates the NRR activity origin of single, double, and triple Fe sites supported by MoS2 but also proposes two valuable strategies from the perspective of kinetics to accelerate the catalysis of NRR: one is by the electric field effect, the other is to use the synergistic effect.