All-Biobased Hydrovoltaic-Photovoltaic Electricity Generators for All-Weather Energy Harvesting

Hygroelectricity generators (HEGs) utilize the latent heat stored in environmental moisture for electricity generation, but nevertheless are showing relatively low power densities due to their weak energy harvesting capacities. Inspired by epiphytes that absorb ambient moisture and concurrently capture sunlight for dynamic photosynthesis, we propose herein a scenario of all-biobased hydrovoltaic-photovoltaic electricity generators (HPEGs) that integrate photosystem II (PSII) with Geobacter sulfurreducens ( G.s ) for simultaneous energy harvesting from both moisture and sunlight. This proof of concept illustrates that the all-biobased HPEG generates steady hygroelectricity induced by moisture absorption and meanwhile creates a photovoltaic electric field which further strengthens electricity generation under sunlight. Under environmental conditions, the synergic hydrovoltaic-photovoltaic effect in HPEGs has resulted in a continuous output power with a high density of 1.24 W/m 2 , surpassing all HEGs reported hitherto. This work thus provides a feasible strategy for boosting electricity generation via simultaneous energy harvesting from ambient moisture and sunlight.