Rare-earth metal-N6 centers in porous carbon for electrocatalytic CO2 reduction

Abstract

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 CO₂ reduction activity of rare earth-N₆ 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 N₆C monolayers in the ten studied Re-N₆C 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 N₆C skeleton. CO is the primary chemical product of electrocatalytic CO₂ 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 CH₄. 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 CO₂ reduction. Subsequently, Eu-N₆C was experimentally synthesized and used for electrocatalytic CO₂ reduction to obtain CO products, and the overpotential showed good agreement with the theoretically calculated values.