Unlocking the catalytic performance of rare earth single atom catalysts for electrochemical nitrogen reduction reaction

Abstract

In the pursuit of green and sustainable ammonia synthesis, there is a growing need to explore beyond traditional transition metals for active sites in single atom catalysts (SACs). Here, a series of SACs with active sites of rare earth (RE) elements is investigated by means of first-principles computations. We systematically evaluate the stability, reaction mechanism, catalytic activity, and selectivity of these catalysts towards the electrochemical nitrogen reduction reaction (NRR). Our results indicate that the alternating mechanism is favorable for NRR on these SACs, and the adsorption free energy of NNH* can predict catalytic activity by volcanic curve. Notably, Ce embedded g-CN (Ce/g-CN) shows high stability and catalytic activity and suppresses the hydrogen evolution reaction. Electronic structure analysis reveals that Ce-5d orbit is mainly responsible for the hybridization with g-CN, while the activation of π* anti bonding orbits relies more on the charge contribution of Ce-4f orbit. Moreover, the activity of the Ce site can be enhanced by the axial coordination of Li element (the limiting potential can reach −0.17 V). This discovery not only broadens the understanding of SACs but also injects new vigor into the SACs family and contributes to the advancement of green ammonia synthesis.