context: All electrochemical measurements were carried out on a CHI 660E electrochemical workstation. The electrochemical properties of the prepared electrodes were tested using a three-electrode system in 1 M H2SO4 aqueous electrolyte. A platinum plate and a saturated calomel electrode (SCE) served as the counter electrode and the reference electrode, respectively. N-PCNFAs and PCNFAs sandwiched tightly between two pieces of 304 stainless steel meshes were directly used as the binder/additive-free working electrodes held by a clamp. To investigate the electrochemical properties, cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS, a frequency response analysis over the frequency range from 100 kHz to 10 mHz) were carried out. The specific capacitance of the electrode material was calculated from discharge curves according to the following equation (eqn (1)): where Cm is the specific capacitance (F g−1), I is the constant discharge current (A), Δt is the discharge time (s), m is the total mass of the active material (g) and ΔV is the set potential window (V).
answer: 1 M H2SO4 aqueous