Hydrogel shields to support and protect catalysts of H2 oxidation and CO2 reduction.

• Applicant: Professor Dr. Nicolas Plumeré
• Subject Area: Analytical Chemistry
• Term: from 2015 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 283974326

The use of metalloenzymes or synthetic inorganic complexes as catalysts in fuels cells or photoelectrochemical cells may open key routes in energy production and in industrial synthesis. However, the intrinsic fragility and oxygen sensitivity of these catalysts has been an obstacle. The German partner in this project has recently demonstrated that hydrogenases, the very efficient but very fragile biological catalysts of H2 oxidation, could be protected from O2 damage upon integration into a specifically designed redox hydrogel, which reduces oxygen at the polymer surface and thus provides self-activated protection from oxygen [Plumeré et al, Nature Chemistry, 2014]. Following the publication of this result, the French and German partners have initiated a collaboration, which already proved fruitful [Fourmond et al, J. Am. Chem Soc., 2015], to rationalize the protection mechanism and optimize the design of the catalyst-polymer films. These recently published results have set the stage for the full investigation that is the goal of this international and interdisciplinary ANR/DFG project.We plan to explore this new concept by examining a variety of configurations (oxidative or reductive catalysis in thick or thin films), using enzymes such as hydrogenases and CO dehydrogenases as models of fragile catalysts. The enzymes, which will be prepared by the French partner, have been selected because they exhibit various properties (reversible or irreversible catalysis, reversible or irreversible inhibition by O2, rates of inactivation and reactivation that can be tuned by protein engineering). A tight collaboration between the two partners is absolutely crucial in this project because understanding how the hydrogel protects the catalysts requires that the kinetic and geometrical properties of the film be determined, and used in realistic mathematical models that take into account the various chemical reactions and diffusion processes occurring in the depth of the film; the models should then be validated by experimental measurements of how the presence of O2 affects the catalytic current, before the knowledge that has been acquired is used to guide the new design of the film (hydrophobicity of the polymer backbone, redox potential of the redox moieties, thickness, load, etc.). The two partners have demonstrated that they have the right expertise to accomplish their parts in the project, and that they can unite their force and knowledge (biochemistry and mathematical modelling in France, polymer design and physical electrochemistry in Germany) by working together.Our ultimate goal is to fully understand the function of these complex systems where the catalysts is embedded into a protective redox-active hydrogel, in order to achieve the best compromise between overall performance, catalyst use and resistance to O2, and thus maximize the utilisation of the catalyst.

• DFG Programme: Research Grants
• International Connection: France
• Partner Organisation: Agence Nationale de la Recherche / The French National Research Agency
• Cooperation Partner: Professor Dr. Christophe Léger