Didier Leonard oral presentation (SN3-Thu4-2-3)
ToF-SIMS Study of Noble Metal-Free and Co-Grafted Dye-Sensitized H2-evolving NiO Photocathodes
1 Institut des Sciences Analytiques (UMR 5280) - Univ Lyon - CNRS-UCBL-ENS de Lyon, 5 rue de la doua, 69100 Villeurbanne, France
2 Laboratoire de Chimie et Biologie des Métaux (UMR 5249 CEA-CNRS-Université Grenoble Alpes), 17 rue des Martyrs, 38000 Grenoble, France
The development of photoelectrochemical cells (PECs) for water splitting is highly demanded to directly convert solar energy into the carbon-free fuel hydrogen (H2). Inspired from the dye-sensitized solar cell technology, the covalent grafting of H2-evolving photocatalytic systems onto suitable transparent conducting oxides recently proved to be efficient . We prepared a novel H2-evolving photocathode by co-sensitizing a nanostructured NiO film with a push-pull organic dye (RBG) and a cobalt diimine dioxime H2-evolving catalyst (CoP) (Figure 1) . This electrode produced H2 with 10% faradaic efficiency under visible light irradiation in aqueous MES buffer (pH 5.5) at an applied potential of 0.14 V vs RHE but exhibited loss of efficiency after a few hours of activity and a post-mortem analysis was undertaken .
ToF-SIMS proved to be a powerful technique both to assess the efficient co-immobilization of the molecular components (RBG and CoP) and to provide detailed identification of the main changes observed at the surface after two hours of activity. Various signatures (including those detected only in the post-mortem analysis) were followed, showing how the variation in surface composition may take place upon use.
Figure 1. Structures of the molecular components RBG and CoP
 N. Queyriaux, N. Kaeffer, A. Morozan, M. Chavarot-Kerlidou, V. Artero, J. Photochem. Photobiol. C 25, 2015, 90-105.
 N. Kaeffer, M. Chavarot-Kerlidou, V. Artero, Acc. Chem. Res. 48, 2015, 1286-1295.
 N. Kaeffer, C. Windle, R. Brisse, C. Gablin, D. Leonard, B. Jousselme, M. Chavarot-Kerlidou, V. Artero, in preparation