Raney-platinum film electrodes for potentially implantable glucose fuel cells. Part 1: Nickel-free glucose oxidation anodes

We present a novel fabrication route yielding Raney-platinum film electrodes intended as glucose oxidation anodes for potentially implantable fuel cells. Fabrication roots on thermal alloying of an extractable metal with bulk platinum at 200 °C for 48 h. In contrast to earlier works using carcinogenic nickel, we employ zinc as potentially biocompatible alloying partner. Microstructure analysis indicates that after removal of extractable zinc the porous Raney-platinum film (roughness factor ∼2700) consists predominantly of the Pt3Zn phase. Release of zinc during electrode operation can be expected to have no significant effect on physiological normal levels in blood and serum, which promises good biocompatibility. In contrast to previous anodes based on hydrogel-bound catalyst particles the novel anodes exhibit excellent resistance against hydrolytic and oxidative attack. Furthermore, they exhibit significantly lower polarization with up to approximately 100 mV more negative electrode potentials in the current density range relevant for fuel cell operation. The anodes’ amenability to surface modification with protective polymers is demonstrated by the exemplary application of an approximately 300 nm thin Nafion coating. This had only a marginal effect on the anode long-term stability and amino acid tolerance. While in physiological glucose solution after approximately 100 h of operation gradually increasing performance degradation occurs, rapid electrode polarization within 24 h is observed in artificial tissue fluid. Optimization approaches may include catalyst enhancement by adatom surface modification and the application of specifically designed protective polymers with controlled charge and mesh size.