DFT insights into nano-Au/carbon nitride: potent CO oxidation facilitated by weak metal–support interaction

The catalytic performance of gold nanoparticles is critically dependent on the nature of the heterogeneous support used. Spin-polarised density functional theory (DFT) calculations with dispersion corrections (DFT-D3) were employed to investigate 1-, 2-, 4-, and 8-layer Au nanosheets supported on cubic C₃N₂ (Au_x@C₃N₂). Crucially, the near-Fermi-level Au 5d band, which is vital for catalytic turnover, remains essentially unchanged across all thicknesses, confirming that the metal's electronic population is largely insensitive to the C₃N₂ substrate. Charge density and electron localisation function analyses confirm that the interface is governed by weak van der Waals forces, evidenced by Au-support separations of approximately 3 Å and negligible mid-bond charge, ruling out covalent or metallic bonding. This weak interaction prevents electron deficiency in the Au atoms, enabling miniaturisation into the sub-nanometre regime. Among the configurations examined, the four-layer nanosheet offers the highest near-E_Fermi 5d occupation, preserving the high intrinsic activity required for potent CO oxidation.