fig4

Figure 4. (A) XRD patterns, (B) Raman spectra and (C) N₂ adsorption-desorption isotherms of ACG-Lys, ACG-Pro, ACG-Gly and ACG-Cys; (D) XPS survey spectra, (E) N 1s spectra and (F) O 1s spectra of ACG-Pro, ACG-Gly and ACG-Cys; (G) CV curves at 10 mV·s^-1, (H) GCD curves at 1 A·g^-1 and (I) Specific capacitance for ACG-Lys, ACG-Pro, ACG-Gly and ACG-Cys electrodes. XRD: X-ray diffraction; XPS: X-ray photoelectron spectroscopy; ACG: activated coffee grounds; CV: cyclic voltammetry; GCD: galvanostatic charge-discharge.