First-row transition metal embedded pyrazine-based graphynes as high-performance single atom catalysts for the CO₂ reduction reaction

Single atom catalysts (SACs) have displayed unprecedented activity and selectivity toward the electrochemical CO₂ reduction reaction (CO₂RR). Herein, first-row transition metal embedded pyrazine-based graphynes (TM-pyGYs) were evaluated as potential SACs for the CO₂RR by using density functional theory. The computational results showed that TM-pyGYs exhibited large cohesive energies ranging from 6.67 to 6.78 eV per atom and metal binding energies ranging from 0.79 to 5.48 eV. Electronic structure analyses demonstrated the strong covalent bond, large charge transfer, and distinct orbital overlap between the TM atoms and pyGY, which proved the high stability of TM-pyGYs in the CO2RR. Most TM-pyGYs exhibited preferred CO₂RR selectivity over the hydrogen evolution reaction. The most favorable reaction pathways of the CO₂RR to CO, HCOOH, CH₃OH, and CH₄ on TM-pyGYs were systematically explored. Among all the TM-pyGYs, Mn/Fe/Ni-pyGYs were determined to be outstanding electrocatalysts in the CO₂RR for producing HCOOH with low limiting potentials of −0.21 to −0.36 V, and Co-pyGY exhibited high-performance CO₂RR to CH₄ with a low limiting potential of −0.35 V, which surpassed the performance of the vast majority of electrocatalysts. With applied potential, Fe/Co/Ni-pyGYs exhibited great advantages in the CO₂RR to CH₄. The results of this work highlighted TM-pyGYs as ideal SACs for the electrochemical CO₂RR.