Bio-inspired [NiFe] Hydrogenase Catalysts for H2 production

点击翻译按钮获取中文摘要

Hydrogen production through water splitting appears to be among the preferred solutions in the long run for the storage of renewable energy. Nature offers efficient H2 evolution catalysts in the form of hydrogenases, organometallic enzymes containing nickel and/or iron sites whose catalytic performances rival commonly used platinum catalysts for hydrogen production. Hydrogenases thus offer fascinating blueprints for the design of new molecular catalysts based on earth-abundant metals, to be implemented in technological devices such as electrolysers or photo-electrochemical cells. However, all heterodinuclear NiFe model systems reported so far do not reproduce the Ni-centered chemistry that occurs at the active site of [NiFe] hydrogenases, and their efficiency is still very low compared to the enzyme.By means of the development of innovative bio-inspired H2 evolution catalysts, our major objectives are (i) to contribute to the full understanding of the catalytic mechanism of the [NiFe] hydrogenase and (ii) to develop efficient mimics of this enzyme that model not only the structure and function of the active site but also its impressive reactivity. This requires that the H+/H2 reactivity and redox events occur at the Ni site of a dithiolato-bridged heterobimetallic NiFe complex. Our preliminary results with the characterization of an unprecedented Ni-centered H+ reduction catalyst, which accurately models multiple states of the [NiFe]-hydrogenase, represent a real breakthrough in this field and will be the foundation of this project. More specifically, we plan to focus on the following points: (i) isolation and characterization of active metal hydride intermediates relevant to the [NiFe]-hydrogenase mechanism, (ii) determination of the crucial structural elements to achieve efficient catalysis with Ni-centered hydrogenase chemistry, (iii) definition of the factors that control the electron and proton transfer sequence during the catalytic cycle, (iv) importance of a proton relay for the performance of the catalysts and role of the second coordination sphere, and (v) effect of replacing a sulfur by a selenium donor atom on the redox and electronic properties of the NiFe complexes, and on their reactivity for H2 evolution and toward O2. The latter will provide important insight into key functional differences between [NiFe] and [NiFeSe] hydrogenases. The French-German consortium involved in this fundamental research project brings together partners who combine all expertise required to reach the ambitious multidisciplinary goals, namely expertise from synthetic coordination chemistry, spectroscopy and kinetics, electrochemistry, catalysis and quantum chemistry.