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

在燃料电池或光电化学电池中使用金属酶或合成无机配合物作为催化剂，可以开辟能源生产和工业合成的关键途径。然而，这些催化剂固有的易碎性和氧敏感性一直是一个障碍。该项目的德国合作伙伴最近证明，氢化酶是一种非常有效但非常脆弱的H2氧化生物催化剂，在整合到一种专门设计的氧化还原水凝胶中后，可以保护氢化酶免受O2损伤，这种水凝胶可以减少聚合物表面的氧气，从而提供自激活的氧气保护[plumer<e:4>等人，Nature Chemistry, 2014]。在这一结果发表后，法国和德国合作伙伴发起了一项合作，并已证明成果丰硕[Fourmond et al .， J. Am.]。化学Soc。[j]，以理顺保护机制，优化催化剂-聚合物膜的设计。这些最近发表的结果为全面调查奠定了基础，这是这个国际和跨学科ANR/DFG项目的目标。我们计划通过研究各种结构（厚膜或薄膜中的氧化或还原催化）来探索这个新概念，使用诸如氢化酶和CO脱氢酶等酶作为脆弱催化剂的模型。这些酶将由法国合作伙伴制备，之所以被选中，是因为它们具有各种特性（可逆或不可逆的催化作用，可逆或不可逆的O2抑制作用，可以通过蛋白质工程调节的失活和再激活速率）。在这个项目中，两个合作伙伴之间的紧密合作绝对是至关重要的，因为要了解水凝胶如何保护催化剂，需要确定膜的动力学和几何特性，并将其用于考虑在膜深处发生的各种化学反应和扩散过程的现实数学模型；在获得的知识用于指导膜的新设计（聚合物主链的疏水性、氧化还原部分的氧化还原电位、厚度、负载等）之前，应该通过实验测量O2的存在如何影响催化电流来验证模型。这两个合作伙伴已经证明，他们有合适的专业知识来完成他们在项目中的部分，他们可以通过合作将他们的力量和知识（法国的生物化学和数学建模，德国的聚合物设计和物理电化学）结合起来。我们的最终目标是充分了解这些复杂系统的功能，其中催化剂嵌入到保护性氧化还原活性水凝胶中，以实现整体性能，催化剂使用和抗氧性之间的最佳折衷，从而最大限度地利用催化剂。

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.