First-principles study on the performance of electrocatalytic nitrogen reduction reaction on MoB2(001) surface

The electrocatalytic nitrogen reduction reaction (NRR) is considered a sustainable method for ammonia (NH3) production due to its high efficiency, low energy consumption and mild reaction conditions. Both the high efficiency and selectivity of the catalyst are the key factors. Transition metal borides (TMBs), as catalytic materials with high stability and excellent electrical conductivity, have been applied to electrocatalytic NRR. MoB2 was chosen as the catalyst, and the activity of its MoB2(001) surface, as well as the NRR mechanism, were investigated by first-principles calculations based on density functional theory (DFT). N2 was adsorbed at the top, bridge, and hollow sites on the MoB2(001) surface, and the intermediates of each step in the reaction path and their free energy for the reduction of N2 to NH3 were studied to explain the NRR mechanism. The results demonstrated that the Mo-top site on the MoB2(001) surface was the most favorable site for NRR. When N2 adsorbs on the top site, the potential determining step of NRR through the alternative mechanism exhibits the closest free energy change to 0, and the limiting potential is −0.27V, indicating excellent catalytic activity on the MoB2(001) surface.