Fig. 4.

Electrochemical tests of cells with gold current collectors and silver electrodes and the proposed working mechanism. (A) OCV of drop-casted cells with gold current collectors and silver electrodes at room temperature with different RH (error bar represents SD, n = 3). (B) Galvanostatic discharge performance at 0.1 μA at 25 °C RH 70%. (C) CV tests of cells at the slow scan rate of 0.1 mV s⁻¹ (25 °C RH 70%). (D) Schematic of the cell working process. When exposed to an ambient environment, the interlayer spacing of GO and rGO increases with moisture absorption, forming nanochannels with a negative surface charge. Highly concentrated solutions were formed between rGO sheets. Hydrated cations were able to migrate from rGO to GO through these channels driven by ion gradient and capillary force, generating a potential difference. Redox reactions on the silver electrode surface then converted this directional ion migration to electron transportation, thus producing electric current.