A 1.6 mW/cm2 Lactate/O2 Enzymatic Biofuel Cell: Enhanced Power Generation and Energy Harvesting from Human Sweat by 3D Interpenetrating Network Porous Structure CNT-Membranes

Abstract

Wearable biofuel cells (BFCs) that rely on human sweat for energy harvesting and power generation require highly active enzymes to modify the electrode for biofuel catalysis and oxidation. However, the aggregation and shedding of biological enzymes leads to coverage and attrition of catalytic active sites, making it difficult to exceed 1 mW/cm2 for current reported BFC power density. An electrode that increases biological enzyme load space and enhances active site area has yet to be developed. Herein, we present CNT-membranes with a 3D interpenetrating hierarchical porous structure enabled by the non-solvent induced phase separation for CNT-bioanode in lactate/O2 BFCs. The interpenetrated porous structure facilitates fast mass transfer kinetics of biofuels and electrolytes, ultralow electron conduction resistance, uniformly and steadily accommodates biological enzymes, and exceptional flexibility that could sustain harsh mechanical deformation. Thus, CNT-bioanode exhibits an impressive power density of 1.6 mW/cm2 when integrated into a BFC with an air-cathode in artificial sweat with only 20 mM lactate. As a human sweat energy harvesting device, 1 cm2 of the CNT-bioanode can operate continuously for 36.8 h and harvest the energy of 4953.6 mJ. Moreover, the device is capable of powering a high-power Bluetooth and sensor integrated circuit, while also being compatible with a customized smartphone app for real-time monitoring of human electrocardiograms. The 3D interpenetrating network porous structure of CNT-membrane establishes an advanced example for the development of future high-performance self-sustainable electronic device systems.