Apart from the activity of the current collector and the ion concentration of the aqueous solution, the surface chemistry of CBNP also affects the output of the AWIEG. Previous work has proved that CBNP film after O 2 plasma treatment generates higher voltage, but the detailed mechanism remains to be explored. To introduce oxygen-containing functional groups on the surface of CBNP, a CBNP h /MCE membrane is treated by O 2 plasma for 45 s at a power of 25 W resulting in a membrane denoted as OCBNP h /MCE, as shown in Figure . After plasma treatment, the CBNP layer shows enhanced hydrophilicity, as proved by the decreased water contact angle (Figure ). This is ascribed to the generation of abundant oxygen-containing groups (i.e., C=O, C-OH, and COOH) on the surface of OCBNP. To eliminate the influence of metal current collectors on the output voltage, a pair of conductive GP strips are used as the current collectors. As shown in Figure and Figure , the CBNP h /MCE-based AWIEG outputs very low voltage and shortcircuit current due to the similar activity of the CBNP and graphite, which are both mainly made of sp 2 hybridized carbon atoms. In contrast, the OCBNP h /MCE-based AWIEG outputs remarkably higher voltage and current, indicating the vital role of oxygen-containing functional groups on OCBNP in enhancing the output electricity.