Figure 5

(a) XPS survey of HPGC-750; high resolution XPS spectra of (b) C 1 s, (c) O 1 s, and (d) N 1 s for HPGC-750; (e) synthetic route to the fabrication of HPGC-T by direct pyrolysis potassium citrate and iron citrate. The synthetic route was drawn using Powerpoint 2019 (https://www.microsoft.com/zh-cn/microsoft-365/get-started-with-office-2019).