Self-healing Fuel Cells by Biological Actuators

A completely novel approach aims to extend the lifetime of polymer electrolyte membrane fuel cells (PEM-FCs) many times over through a self-healing mechanism, thus contributing to the transition to a sustainable economy and mobility. Many start-up cycles in truck or car applications lead to pinholes in the proton-conducting polymer membranes (Nafion™). Since there is no way to repair this type of defect when the fuel cell is already assembled, the performance of the fuel cell stack is continuously reduced towards the end of its lifetime. The BioHealing project, an interdisciplinary consortium at the Karlsruhe Institute of Technology, investigates an innovative biohybrid technology that can repair occurring pinholes selectively in fuel cell membranes by a self-healing mechanism without disassembling the fuel cell stack. This is enabled by a biohybrid system, i.e., integrating biological and technical components. The filler-forming enzymes are functionally immobilised on the polymer membrane surface via a special peptide linker to enable site-directed filler production during membrane electrode assembly. For self-healing, a substrate is injected into the gas inlet of the fuel cell stack, the enzymatic reaction is catalysed, and the substrate is converted into the filler, a biological polymerised product that seals the existing pinholes. In this publication, the concept is presented with initial research results. The concept includes characterisation of surface properties and functional groups of the Nafion™ membrane, immobilisation of the specially designed fluorophilic peptide linker, selection of suitable enzymes to be screened for activity and stability, and investigation of the filler to be successfully esterified with the membrane.