High Ionic Seebeck Effect in Natural Leaves

Plants actively transport ions to sustain life, yet their capacity to convert heat to electricity via the ionic Seebeck effect has remained unexplored. Here, it is demonstrated that natural Ficus elastica leaves can generate ionic thermovoltages up to 7 V under mild temperature gradients, achieving a high ionic figure of merit of ∼5.6 at room temperature. This pronounced thermoelectric response arises from anion thermodiffusion through the apoplast and is significantly amplified by leaf desiccation and electrode selection. A dielectric capacitive model accounts for the observed enhancement. Notably, living leaves generate thermopower under light-induced temperature gradients, underscoring the potential of in vivo ionic thermoelectric assays. These findings reveal an unrecognized energy-harvesting function in plant tissue and introduce a biodegradable platform for sustainable thermal-to-electrical energy conversion.