Composite interfaces of g-C₃N₄ fragments loaded on a Cu substrate for CO₂ reduction

Designing an electrocatalyst with high efficiency and product selectivity is always crucial for an electrocatalytic CO₂ reduction reaction (CO₂RR). Inspired by the great progress of two-dimensional (2D) nanomaterials growing on Cu surfaces and their promising CO₂RR catalytic efficiencies at their interfaces, the unique performance of Cu-based 2D materials as high-efficiency and low-cost CO₂RR electrocatalysts has attracted extensive attention. Herein, based on density functional theory (DFT) calculations, we proposed a composite structure of graphitic carbon nitride (g-C₃N₄) fragments loaded on a Cu surface to explore the CO₂RR catalytic property of the interface between g-C₃N₄ and the Cu surface. Three composite interfaces of C₃N₄/Cu(111), C₃N₄/Cu(110) and C₃N₄/Cu(100) have been studied by considering the reaction sites of vertex nitrogen atoms, edge nitrogen atoms and the nearby Cu atoms. It was found that the C₃N₄/Cu interfaces where nitrogen atoms contact the Cu substrate present competitive CO₂RR activity. Among them, C₃N₄/Cu(111)-N3 exhibited a better activity for CH₃OH production, with a low overpotential of 0.38 V. For HCOOH and CH₄ production, C₃N₄/Cu(111)-Cu and C₃N₄/Cu(100)-N1 have overpotentials of 0.26 V and 0.44 V. The electronic analysis indicates the electron transfer from the Cu substrate to the g-C₃N₄ fragment and mainly accumulates on the nitrogen atoms of the interface. Such charge accumulation can activate the adsorbed CO bond of CO₂ and lead to lower energetic barriers of CO₂RR. DFT calculations indicate that the boundary nitrogen sites reduced the energy barrier of *CHO, which is crucial for CO₂RR, compared with that of the pristine Cu surface. Our study explores a new Cu-based electrocatalyst and indicates that the C₃N₄/Cu interface can enhance the activities and selectivity of CO₂RR and open a new strategy to design high-efficiency electrocatalysts for CO₂RR.