Modification of the Coordination Environment of Active Sites on MoC for High-Efficiency CH_4 Production

摘要

Modulating the coordination environment of active sites on catalyst surfaces is crucial to developing effective catalysts and controlling catalysis. However, this may be a highly challenging procedure. Guided by the first-principles calculations, the modification of the coordination environment of active sites on MoC nanoparticle surfaces is experimentally accomplished by anchoring pyridinic N atom rings of holey graphene on Mo atoms. The rings produce electrostatic forces that enable the tuning of the Mo sites ' affinity to reaction intermediates, which passivates Mo hollow sites, activates Mo top sites, and reduces the overadsorption of OH on the Mo active sites, as predicted by calculations. The atomic-level modification is well confirmed by atomic-resolution imaging, high-resolution electron tomography, synchrotron soft X-ray spectroscopy, and operando electrochemical infrared spectroscopy. Consequently, the Faradaic efficiency for CO2 reduction to CH4 is enhanced from 16% to 89%, a record high efficiency so far, in aqueous electrolytes. It also exhibits a negligible activity loss over 50 h.