||New directions are urgently needed in energy technologies, and in particular in hydrogen technologies, to raise efficiency and stability of the systems while lowering their cost. Bio-inspiration has a great potential to making breakthroughs in research and development. In particular hydrogenase enzymes compete with platinum as catalysts for H2/H+ interconversion and such an activity can be reproduced in synthetic mimics  but such molecular systems are often challenged by solid-state catalysts, both in terms of activity and stability. We will show how the immobilization of biomimics onto surfaces allows the preparation of highly active electrode materials compatible with existing PEM electrolysis technology . Besides, we will also revisit the structure of reactivity of amorphous molybdenum sulfide, which actually stands as a coordination polymer, therefore bridging the molecular and soli-state sides of H2/H+ catalysis . Besides, we will also describe our effort towards the combination of such catalysts with various photoactive motifs for the preparation of photoelectrode materials that can be implemented into photoelectrochemical (PEC) cells for water splitting [4-7].
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 F. Jaouen, D. Jones, N. Coutard, V. Artero, P. Strasser, A. Kucernak, Toward Platinum Group Metal-Free Catalysts for Hydrogen/AirProton-Exchange Membrane Fuel Cells, Johnson Matthey Technology Review, 62 (2018) 231-255.
 P.D. Tran, T.V. Tran, M. Orio, S. Torelli, Q.D. Truong, K. Nayuki, Y. Sasaki, S.Y. Chiam, R. Yi, I. Honma, J. Barber, V. Artero, Coordination polymer structure and revisited hydrogen evolution catalytic mechanism for amorphous molybdenum sulfide, Nat. Mater., 15 (2016) 640-646.
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 N. Kaeffer, J. Massin, C. Lebrun, O. Renault, M. Chavarot-Kerlidou, V. Artero, Covalent Design for Dye-Sensitized H2-Evolving Photocathodes Based on a Cobalt Diimine?Dioxime Catalyst, J. Am. Chem. Soc., 138 (2016) 12308-12311.
 C.D. Windle, J. Massin, M. Chavarot-Kerlidou, V. Artero, A protocol for quantifying hydrogen evolution by dye-sensitized molecular photocathodes and its implementation for evaluating a new covalent architecture based on an optimized dye-catalyst dyad, Dalton Trans., 47 (2018) 10509-10516.