Photocatalytic Hydrogen Production from Noble Metal Free Systems

Abstract

With the global energy demand constantly rising, the need for developing new abundant and environmentally benign sources of energy is ever increasing.1 Consequently, solar energy is expected to play an increasingly important role in the future. One of the major strategies for solar energy conversion that is currently under development is the light-driven splitting of water into its constituent elements. Inspired by nature’s extensive use of metalloporphyrins as solar energy harvesters and electron transfer agents, artificial porphyrins have found prominent use as photosensitizers in hydrogen producing schemes.2The photocatalytic production of hydrogen can be accomplished by systems containing a photosensitizer, an electron relay, a sacrificial electron donor and a catalyst. The great challenges that remain in the field include the development of systems, which employ earth-abundant materials, and the improvement of the systems activity and durability.Here, we report two noble metal free bioinspired photocatalytic systems, which use porphyrins or a corrole as photosensitizers and the cobaloxime as a catalyst (Figure 1). In the first one a water soluble Zn porphyrin was used as the photosensitizer and [CoIII(dmgH)2(py)Cl)] as the catalyst (Figure 1 left part). This system is effective in photoinduced H2 production in MeCN/water 1:1 with TEOA as a sacrificial donor.3 In the second one the photosensitizer is directly coordinated to the cobaloxime catalyst (Figure 1 right part). From transient absorption studies we observed an electron transfer from the chromophore to the cobalt catalyst, whereas the photocatalytic H2 production was low.4 REFERENCEST. S. Teets, D. G. Nocera, Chem. Commun. 2011, 47, 9268.J. R. Darwent, P. Douglas, A. Harriman, G. Porter, M. C. Richoux, Coord. Chem. Rev. 1982, 44, 83.T. Lazarides, M. Delor, I. V. Sazanovich, T. M. McCormick, I. Georgakaki, G. Charalambidis, J. A. Weinstein, A. G. Coutsolelos, Chem. Commun. accepted, DOI: 10.1039/C3CC45025B.K. Peuntinger, T. Lazarides, D. Dafnomili, G. Charalambidis, G. Landrou, A. Kahnt, R. P. Sabatini, D. W. McCamant, D. T. Gryko, A. G. Coutsolelos, D. M. Guldi, J. Phys. Chem. C, 2013, 117, 1647.