Atomically dispersed Cu and Fe on N-doped carbon materials for CO electroreduction: insight into the curvature effect on activity and selectivity.

CO electroreduction reaction (COER) by single metal sites embedded in N-doped graphene (M@N-Gr, M = Cu and Fe) and carbon nanotubes (M@N-CNT, M = Cu and Fe) has been explored by extensive first-principles calculations in combination with the computational hydrogen electrode model. Both atomically dispersed Cu and Fe nanostructures, as the single atom catalysts (SACs), have higher selectivity towards COER, compared to hydrogen evolution reduction (HER), and they can catalyze COER to CO, HCOOH, and CHOH. In comparison with Cu@N-Gr, the limiting potentials for generating CO, HCOOH, and CHOH are reduced obviously on the high-curvature Cu@N-CNT. However, the curvature effect is less notable for the single-Fe-atom catalysts. Such discrepancies can be attributed to the d-band center changes of the single Cu and Fe sites and their different dependences on the curvature of carbon-based support materials.