Strain Engineering: an efficient strategy to enhance the catalytic activity of SACs on waved graphene for e-NRR
Ammonia is an important chemical in both industry and agriculture. How to produce ammonia in a green way has been a challenging issue. Electrochemical nitrogen reduction reaction (e-NRR) has been proposed to reach the purpose. However, the technology is still far from practical application due to low production, which is mainly induced by inefficient electrocatalyts. In this work, we design a series of single-atom catalysts (SACs) anchored in waved-graphene (wG) for efficient e-NRR and systematically investigate the effect of curvature on the catalytic performance based on first-principles calculations. Eight SACs (V, Cr, Mn, Fe, Co, Ni, Cu, Zn, and Pt) anchored on waved-graphene with various curvatures (0-50%) are studied. We find that the curvature strongly affect the formation, catalytic activity, and selectivity for e-NRR of SACs: (1) the formation possibility of SACs in wG is greatly enhanced with the increasing curvature; (2) the free energies for the rate-determining steps of SAC-V-wG, SAC-Mn-wG, and SAC-Cr-wG are less than 1.0 eV, leading high catalytic activity for e-NRR. Especially, SAC-Mn-wG shows higher activity for e-NRR than the SAC-Mn on flat graphene. (3) The three systems have higher selectivity for e-NRR than for HER, which can be further highly improved by the compression. We conclude that SAC-Mn-wG is the best SAC on wG for e-NRR because of the easy fabrication, good catalytic performance and high selectivity. We believe that our findings provide new insights on reported experimental results and guidance on the design of novel SACs with high performance for e-NRR.