▎ 摘　　要

Electrocatalytic conversion of nitrogen oxides is a promisingapproachto address nitrogen pollution in underground water. Nitrogen oxides,such as nitrate and nitrite, can be reduced to N-2 and NH3 over an electrocatalyst, with NO as the key intermediate,subsequent reaction of which controls the overall activity and selectivity.Here, we report density functional theory calculations of NO electrocatalyticreduction (NOER) over lanthanum embedded in graphene, through whichwe show that the localized states in La drive the reaction favorablydue to more pronounced molecular adsorption and charge transfer thantransition metals such as Co. The free energy profiles are comparedbetween the La-based single-atom catalyst (SAC) and Co-based SAC,for producing N-2 and NH3. We find that the La-SACintensifies the electron transfer to the adsorbed NO, promoting thefirst protonation step of NO, which is the potential-limiting stepon the Co-SAC. Also, an intriguing effect of the water solvent isrevealed on the La-SAC. In addition to stabilizing the intermediatespecies, water molecules that are coordinated with La participatedirectly in the protonation steps, enhancing the catalyst activity.This study reveals the unique mechanism of NOER over rare-earth-basedcatalysts, highlighting the potential application of atomically dispersedf-block elements for electrocatalytic reactions.