Extended Data Fig. 4: Atomic characterization of nanopore density and size.

a, An STM image of 80 × 80 nm². Corrugation with terrace width of about 20 nm was induced by the Cu substrate. Bright and dark dot features were observed in a large density compared with the conventional CVD graphene on Cu. b, Close-up STM image with atomic resolution for the area of the rectangle in a. Arrows indicated nanopore structures. c, Close-up STM image with atomic resolution for the area of the rectangle in b. The size of the nanopore is about 1 nm. The honeycomb structure of graphene is indicated with an inset of honeycomb cells. Nanopore density of 3.875 × 10¹² cm⁻² was counted in STM images, based on the characterization of the atomic resolution. d–g, CAFM images of pristine graphene and nanoporous graphene samples with different nanopore diameters. The acquirements of the nanopore area are indicated by the white outlines. The diameter of the nanopore is calculated by using \(d=2\sqrt{A/\pi }\), in which A is the area of the nanopore. h,i, The experimental diameter distribution of samples #822 and #835, respectively. j,k, The simulated diameter distribution of samples #822 and #835, respectively.