D8 focus diffraction system

The structures of the samples were determined using a Hitachi S-4800 scanning electron microscope (SEM, 3 kV). Powder X-ray diffraction (XRD) patterns were collected using a Bruker D8 Focus Diffraction System using a Cu Kα source (λ = 0.154178 nm). Transmission electron microscopy (TEM), higher-magnification transmission electron microscopy (HRTEM) and elemental distribution mapping images were taken on a JEOL-2100F system equipped with EDAX Genesis XM2. The thickness of the nanosheets was determined using atomic force microscopy (AFM) (Bruker multimode 8). X-ray photoelectron spectroscopy (XPS) measurements were conducted with a PHI-1600 X-ray photoelectron spectrometer equipped with Al Kα radiation. All binding energies were referenced to the C 1s peak at 284.8 eV.

The scanning electron microscopy images were acquired from a Hitachi S-4800 scanning electron microscope. Transmission electron microscopy and high-resolution transmission electron microscopy images were taken using a JEOL-2100F system. The XRD was measured using a Bruker D8 Focus Diffraction System with a Cu Kα source (λ = 0.154178 nm). X-ray photoelectron spectrum analysis was recorded via a PHI 5000 Versaprobe system using monochromatic
Al Kα radiation. All binding energies were revised according to the C 1-s peak at 284.8 eV. The ultraviolet-visible (UV-Vis) absorbance spectra were measured on a Beijing Purkinje General T6 new century spectrophotometer. Anion chromatography was performed on an ICS-1100, Thermo. Cation chromatography was conducted on an ICS-900, Thermo. The concentration of ¹⁵N isotope labeling was established by isotopic mass spectrometry (MAT-271). The pH values of the electrolytes were determined using a pH-meter (LE438 pH electrode, Mettler Toledo, USA).