Rare-earth metal-N 6 centers in porous carbon for electrocatalytic CO 2 reduction.

Single-atom catalysts fabricated using rare earth elements have emerged for electrocatalytic carbon dioxide reduction, but they need to be studied systematically and intensively. Herein, density functional theory was employed to determine the electrocatalytic CO 2 reduction activity of rare earth-N 6 porous carbon (Re = Ce, Nd, Sm, Eu, Gd, Tb, Er, Tm, Yb, and Lu) single-atom catalysts. The results revealed that the binding energy of the rare-earth atoms to the N 6 C monolayers in the ten studied Re-N 6 C monatomic catalysts is much more negative than the cohesion energy of the bulk rare-earth metal, which makes rare-earth atoms stably dispersed in the N 6 C skeleton. CO is the primary chemical product of electrocatalytic CO 2 reduction by Ce, Eu, and Lu. The primary product of the six monatomic species, i.e. , Nd, Sm, Tb, Er, Tm, and Yb, is HCOOH. The dominant product of Gd is CH 4 . The limiting potentials of these catalysts are in the range of 0.31-0.786 V and their overpotentials are in the range of 0.06-0.707 V, all of which are relatively low, showing that they are potential and promising electrocatalysts for CO 2 reduction. Subsequently, Eu-N 6 C was experimentally synthesized and used for electrocatalytic CO 2 reduction to obtain CO products, and the overpotential showed good agreement with the theoretically calculated values.