Electronic structure modulation via curvature engineering enables C-C/C-N coupling on Co-graphdiyne for selective CO₂...

Single-atom catalysts provide maximum atomic utilization for CO₂ electroreduction (CO₂RR), yet achieving high selectivity while suppressing the competing hydrogen evolution reaction (HER) remains challenging. Here, density functional theory calculations demonstrate that curvature engineering of Co-graphdiyne (Co-GDY) effectively modulates the electronic structure of the Co active site and enhances catalytic performance. It was observed that the planar Co-GDY configuration exhibits a limiting barrier of 0.45 eV for CO₂-to-CH₄ conversion but suffers from significant HER competition due to excessive negative charge accumulation on the carbon atoms surrounding the Co center. Introducing a tubular curvature redistributes the local charge density, weakens Coulombic repulsion, suppresses HER, and reduces the limiting barrier to 0.40 eV. Beyond C₁ products, the modified structure stabilizes CH₂O intermediates and enables efficient C-C coupling with a low kinetic barrier of 0.29 eV, requiring only 0.14 V for C₂H₄ formation. Strong CO adsorption and favourable N₂ activation on the modified structure further allow feasible C-N coupling toward CO(NH₂)₂ synthesis under low applied potential. These findings establish curvature modulation as an effective strategy for designing multifunctional electrocatalysts for sustainable carbon utilization.