Moisture-enabled hydrovoltaic power generation with milk protein nanofibrils

Biologic materials have been shown to be good candidates for moisture-enabled hydrovoltaic power generation, but only those from specific bacterial cells have been explored. Herein, we report a moist-electric generator (PN-MEG) based on protein nanofibrils from milk β-lactoglobulin. The as-developed device can generate an open-circuit voltage of up to 0.65 V and a short-current of 2.9 µA. This device can generate a maximum power density of 38.88 μW·cm−2, which is one order of magnitude larger than those of previously reported analogous devices. The superior performance of this device is attributed to the remarkable hydrophilicity, high ionization and surface-to-volume ratio of protein nanofibrils. Density functional theory (DFT) calculations revealed that carboxyl groups were the favorable active sites in protein nanofibrils for binding water molecules. This study provides a novel perspective for common protein nanofibrils and paves the way for developing high-performance hydrovoltaic devices from biological materials.