03 Fakultät Chemie

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Institute: search.filters.UBSInstitut.Institut für Technische ChemieAuthor: search.filters.author.Slageren, Joris van

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    Remarkable enhancement of catalytic activity of Cu‐complexes in the electrochemical hydrogen evolution reaction by using triply fused porphyrin
    (2022) Chandra, Shubhadeep; Singha Hazari, Arijit; Song, Qian; Hunger, David; Neuman, Nicolás. I.; Slageren, Joris van; Klemm, Elias; Sarkar, Biprajit
    A bimetallic triply fused copper(II) porphyrin complex (1) was prepared, comprising two monomeric porphyrin units linked through β-β, meso-meso, β′-β′ triple covalent linkages and exhibiting remarkable catalytic activity for the electrochemical hydrogen evolution reaction in comparison to the analogous monomeric copper(II) porphyrin complex (2). Electrochemical investigations in the presence of a proton source (trifluoroacetic acid) confirmed that the catalytic activity of the fused metalloporphyrin occurred at a significantly lower overpotential (≈320 mV) compared to the non‐fused monomer. Controlled potential electrolysis combined with kinetic analysis of catalysts 1 and 2 confirmed production of hydrogen, with 96 and 71 % faradaic efficiencies and turnover numbers of 102 and 18, respectively, with an observed rate constant of around 107 s-1 for the dicopper complex. The results thus firmly establish triply fused porphyrin ligands as outstanding candidates for generating highly stable and efficient molecular electrocatalysts in combination with earth‐abundant 3d transition metals.
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    Hydrogen spillover through hydride transfer : the reaction of ZnO and ZrO2 with strong hydride donors
    (2024) Benz, Michael; Bunjaku, Osman; Nowakowski, Michal; Allgaier, Alexander; Biswas, Indro; Slageren, Joris van; Bauer, Matthias; Estes, Deven P.
    Hydrogen spillover, transfer of H2 from a metal surface to a support (often metal oxides), is pivotal for many heterogeneous catalytic processes, including Cu/ZnO and Cu/ZrO2 catalyzed methanol synthesis. Little is known about hydrogen spillover on ZnO or ZrO2, due to the high complexity of the metal-metal oxide interface. Here, we model hydrogen spillover on ZnO and ZrO2 by reacting them with molecular metal hydrides to see how the properties of the hydrides affect hydrogen spillover. While the good H· donors HV(CO)4dppe (1) and CpCr(CO)3H (2) do not react with the metal oxide surfaces, the strong hydride donors iBu2AlH (3), Cp2ZrHCl (4), and [HCu(PPh3)]6 (5) do reduce ZnO and ZrO2 to give defect sites with the same EPR signatures as obtained via hydrogen spillover. We also observe new M-O bonds to the surface using X-ray absorption spectroscopy (XAS). We propose that these metal oxides undergo hydrogen spillover via initial hydride transfer followed by tautomerization of the surface hydride, giving reduced sites and OH bonds. This mechanism is in contrast to the traditional spillover mechanism involving discrete proton- and electron transfer steps. We also observe that ZnO is easier to reduce than ZrO2, explaining the difficulty observing spillover on Cu/ZrO2.