To investigate the mechanism of OCBNP h /MCE-based AWIEG, it was short-circuited to discharge for 12 hours under intermittent addition of water. The surface chemistry of the OCBNP layer and wet-end GP strip before and after discharge was characterized by XPS. As shown in Apart from the contribution of water-induced electrochemical redox reactions to the electricity generation of OCBNP h /MCE-based AWIEG, the effect of water-induced dissociation of oxygencontaining groups on the surface of OCBNP into negatively charged groups and mobile protons (H + ) on the output voltage could not be neglected. This is because many active materials (e.g., GO, polyacrylic acid (PAA), and polystyrene sulfonic acid bearing similar functional groups can generate electricity upon exposure to moisture due to the dissociation and diffusion of H + . To investigate this effect, an aqueous OCBNP suspension was obtained by ultrasonication of an O 2plasma-treated CBNP coating on a glass slide in water. As shown in Figure , the pH value of the OCBNP suspension is about 4.5, which is a bit more acidic than the ambient water (Figure ), implying that the functional groups of the OCBNP layer dissociate into mobile protons and immobile negatively charged groups. Therefore, the acidity of water will affect this dissociation process thus the output voltage of the AWIEG. To investigate this effect, four kinds of aqueous liquids with different acidity were added on the blank end of four OCBNP h /MCE-based AWIEGs, respectively. As shown in Figure and Figure , the output voltage of the AWIEG increases with the increment of acidity (decreasing pH values, as shown in Figure ) of the liquid. It is also found that the zeta potential of OCBNP increases obviously with the increase of pH (2-11) due to the ion-dependent dissociation of the oxygen-containing groups (Figure ), which can be the reason for the pH-dependent output voltage of the AWIEG. It is expected that the alkali electrolyte (e.g., 1 M NaOH) can promote the dissociation of oxygen-containing groups (e.g., -COOH, -C-OH) on OCBNP into negatively charged groups (-COO -and -C-O -) that induce a more negative surface potential on the OCBNP (Figure ), which reduces the total potential of the OCBNP layer (the anode). On the contrary, the strong acidic electrolyte can inhibit the dissociation of oxygencontaining groups and increase the surface potential of OCBNP and the total potential of the anode.