Fig. 1: Designing strategies of ion-electron conversion enhanced moisture energy harvester (i-eMEH).

a Schematic diagram of the electrode interface and the corresponding output performance of moisture-electricity generators with inert electrode. The insufficient ion storage on electrode will influence the ion-electron conversion at the interface, manifesting in low peak current. The formation of built-in electric field causes the rapid decay of voltage and current. b Schematic diagram of the electrode interface and the output performance of moisture-electricity generators with increased capacitance. The capacitive interface layer promotes the ion-electron conversion, bringing about the increase in peak current and voltage. The restricted formation of built-in electric field weakens the decay rate of voltage and current. c Schematic diagram of the electrode interface and the output performance of i-eMEH with increased capacitance and faradic process. The introduction of redox couples at the interface creates a faradic process for further enhanced ion-electron conversion. The electron transferred in this way can also screen the ionic charge in the interface to stabilize the electrode potential and increase the amounts of ions stored on the electrode. The electron transfer will undergo opposite directions under open-circuit and short-circuit condition.