A new fuel cell that works with the enzyme hydrogenase is as efficient as those that contain expensive platinum as a catalyst. The enzymes require an aqueous environment, which makes it difficult for hydrogen to reach the enzyme-loaded electrode. Previously developed concepts for packaging the enzymes were combined with gas The researchers carried out biofuel cell tests in this electrochemical cell. Source: Ruhr-Universität Bochum, Marquarddiffusion electrode technology to overcome this limitation.

Gas diffusion electrodes efficiently transport gaseous raw materials for a chemical reaction to the electrode surface with the catalyst. In past research, the catalyst was electrically wired directly to the electrode surface so that only a single layer of enzyme can be applied to the electrode, which limits current flow. Hydrogenase must be shielded from environmental agents because it is unstable in the presence of oxygen.

A redox polymer was formulated to embed and protect the enzymes from oxygen. To combine the hydrophobic electrodes and hydrophilic enzymes, an electron-transferring adhesive layer was applied to the electrode surface. The enzyme-laden polymer matrix, synthesized with an optimal balance of hydrophilic and hydrophobic properties, was then applied to the electrode.

The electrodes remained permeable to gas and the polymer matrix was demonstrated to function as an oxygen shield for porous 3D electrodes. A current density of 8 milliamps/sq cm was documented. A fuel cell assembled with the bioanode and a biocathode achieved a power density of up to 3.6 mW/sq cm and an open circuit voltage of 1.13 V, which is just below the theoretical maximum of 1.23 V.

Researchers from Ruhr-Universität Bochum, the Max Planck Institute for Chemical Energy Conversion and the University of Lisbon contributed to this development, which is described in Nature Communications.