Three-dimensional graphene-polypyrrole hydrogel as cathode for a bioelectric Mg-air battery

A bioelectric Mg-air battery offers a promising solution for powering implantable medical devices due to obvious merits such as easy miniaturization and ease of battery package. One of the key challenges in bioelectric battery is to seek air cathode materials with both satisfied electrocatalytic activity and good biocompatibility. 3D graphene macroassembly is the material of interest in metal air batteries as well as bioelectronics. For further performance enhancement, it is essential to incorporate other materials with better electrocatalytic performance into graphene matrix. Polypyrrole (PPy) has been intensively implemented in biomedical applications and energy storage for its biocompatibility and versatile properties including inherent electrocatalytic activity. In this work, a graphene-PPy composite was prepared based on a paper-like graphene hydrogel scaffold via facile interfacial gelation, and followed by PPy electrodeposition. The obtained G-PPy gel exhibited excellent performance in a Mg-air bioelectric battery, with stable voltage output of 1.15 V and 13.6 mAh cm⁻² at 200 μA cm⁻².